One of the very first pieces of equipment the new biomed is likely to encounter is an intravenous or “IV” pump. It is one of the most common pieces of medical equipment found in a hospital or large clinic, found in the hundreds in large facilities (or in the shop awaiting repair), so it is about time the fundamentals of this device are revealed. The basic IV setup consists of a sterile liquid source, formerly a glass bottle but nowadays a plastic bag, a drip chamber with an attached spike, a length of plastic tubing approximately 48 inches long, a roller clamp, an auxiliary clamp, one or more injection ports, and a needle end. This setup depends on gravity to deliver a prescribed liquid directly into the patient’s vein. The liquid source is generally a disposable container holding a liter of a prescribed fluid. This fluid can be normal saline (9 g of salt per 1000 mL sterile water added to provide a 0.9% saline solution, the same salt concentration as body fluid), to provide simple hydration. A solution of 5% dextrose in water (D5W) is used to provide both hydration and basic nutrition. Another common fluid is Ringer’s lactate (also called lactated Ringer’s or Hartmann’s solution) which consists of sterile water with calcium chloride, potassium chloride, sodium chloride, and sodium lactate added— typically used for rapidly restoring lost blood volume and depleted electrolytes. The drip chamber containing the bag spike performs two functions. One is to penetrate the seal of the sterile liquid source. This allows fluid to enter the drip chamber through an integral needle. When properly set up, the drip chamber is approximately half-full of fluid with air taking up the remaining space. When hanging, the drip chamber supplies the IV tubing with fluid. The roller clamp totally surrounds a short section of the IV tubing and contains a slanted raceway holding a small knurled wheel. When the nurse rolls the wheel all the THE FUNDAMENTALS OF ...

The heart is the cell-nourishment pump of the body. Moving blood oxygenates tissues, pumps nutrients to virtually every cell in the body, and disposes of cell waste. As long as the muscle fibers of the heart operate in precise synchronization, everything is fine. When this vital organ malfunctions, we risk death. One of the more common malfunctions of the heart is ventricular fibrillation, where the heart stops its powerful pumping action and just twitches and quivers instead. This quivering action does not move blood throughout the body efficiently or effectively. Another malfunction is ventricular tachycardia, where the heart is in a “run away”-like state, beating at more than 100 times a minute and with three or more irregular beats in a row. These are the main heart malfunctions that a defibrillator can correct.The world of defibrillators consists of three basic types—external manual, automated external, and implantable (or internal). All three have the same goal—to deliver a life-saving electric shock that restores the normal electrical activity of the patients' heart—but they do so in different ways and under different circumstances. Next to intravenous pumps and electronic thermometers, the external defibrillator is one of the most common pieces of medical equipment found in a hospital or large clinic. One is usually located on each ward, in each clinic, and even the operating room area because they are typically found on every crash cart in the facility. One of the items found in many modern police squad cars is an automated external defibrillator (AED), which is a close cousin of the external manual defibrillator. Selected patients have an internal defibrillator surgically implanted to continuously monitor heart rhythm and deliver appropriate shocks as necessary. This article will delve a bit into each of the three types of defibrillators.All defibrillators have two things in common—they contain circuitry to deliver the lifesaving electrical shock and circuitry to monitor the heart and determine when that shock is indicated. Of the three types, only the two external defibrillators are likely to reach the biomedical electronic technician's bench. The external manual defibrillator is the one that comes to most peoples' minds when one says “defibrillator.” It is the one found on hospital crash carts and ambulances. To overcome thoracic impedance while delivering the lifesaving shock to the heart, both types of external defibrillators provide as much as 360 joules (J) of energy in a single 20-millisecond impulse of between 2 and 4 kilovolts (kV) to the patient.The external manual defibrillator also contains a monitor to display an electrocardiograph for the provider to use in determining the appropriate treatment. The original models featured only a three-lead electrocardiogram (ECG) capability, but most modern units can perform full 12-lead ECGs, determining lead selections using a hard or soft switch. Likewise, all modern and most legacy units are powered either by internal batteries or line power from a convenience outlet. As a safety feature, these devices will operate on line power, regardless of the presence or condition of the internal battery. Likewise, early and legacy models delivered a monophasic waveform, providing a single positive pulse of energy, while the newest models now deliver a biphasic waveform, providing a positive pulse followed by a negative pulse.Studies have shown that patients receiving biphasic shocks correct both ventricular fibrillation and tachycardia more successfully than those receiving monophasic shocks. Additionally, some external manual defibrillators also incorporate a pacemaker for temporary treatment of asystole, bradycardia, sick sinus syndrome, certain types of tachycardia, or any other condition requiring an external pacemaker.External manual defibrillators normally connect their monitor to the patient with conventional ECG electrodes, lead wires, and patient cable. Defibrillation is accomplished using two hand-held insulated paddles that usually also allow the user to view an ECG signal when there is insufficient time to “wire” the patient to the monitor. To deliver the stored energy to the patient, the user must simultaneously press the discharge buttons located on each paddle. Pacemaker-equipped external defibrillators also can use self-adhesive electrode pads for both defibrillation and pacing.After connecting the external manual defibrillator, based upon the providers' impression and diagnosis, the patient may only require the administration of oxygen and/or other drugs, as well as continued monitoring. In other cases, the provider determines that a shock is required, the correct energy level to deliver to the patient, and how often to deliver this level before trying a higher level or some other action. Oftentimes, the administration of both drugs and shocks is required to return the patient's heart to sinus rhythm.Most external manual defibrillators also have an internal mode used to restart hearts near the final stage of open-heart surgery. In this mode, their output is limited to 50 J by design because it is used directly on the heart in an open chest. Another mode found in these defibrillators is the synchronized cardioversion (sync) mode. The sync mode is typically used to cardiovert patients in ventricular tachycardia, which requires the delivery of the shock precisely with the peak of the R-wave. In the sync mode, discharge is inhibited until the defibrillator locks onto the R-wave and then discharges with the peak of the next R-wave. The sync mode prevents discharge during cardiac repolarization, represented by the T-wave, where the shock could cause the heart to fibrillate.Automated external defibrillators, or AEDs as they are more commonly known, oftentimes are part of a public accessible defibrillator (PAD) program. Properly administered PAD programs place defibrillators in areas where certain members of the public, such as security guards, flight attendants, police officers, nonparamedic fire fighters, and other AED-certified individuals, can access them in an emergency. AEDs are not, as many believe, as easy to use as a fire extinguisher. Neither are they intended to be used by untrained casual passers-by to an apparent heart attack.These units come in one of two varieties—fully and semi-automated. Both varieties are powered by internal batteries (only) and contain essentially the same circuitry as the external manual defibrillator to provide the 2- to 4,000-volt biphasic waveform to externally cardiovert the patient. However, the primary difference is that the AED—not a healthcare provider—determines if the shock is required. AEDs acquire cardiac information and deliver their shock through large self-adhesive conductive pads applied to the thorax on either side of the heart, and they use an algorithm to determine if a victim will benefit from defibrillation.If defibrillation is indicated, automatic units alert first responders to stay clear of the patient, and then automatically deliver the required shock. Semi-automated units make the same algorithm-based determination, but depend on the first responder to push a button to deliver the lifesaving shock. Both varieties provide some form of instruction to user personnel, usually both audible and visual, such as when to provide cardio-pulmonary resuscitation (CPR), when to stop, when it is analyzing, and before shocking the patient. Some models even produce a metronome-like ticking sound at the ideal tempo for performing CPR and have both event and audio recording capabilities to document the episode for legal reasons.Because these hermetically sealed pulse generators are implanted in the patient during a surgical procedure and are regulated like other implantable medical devices (such as artificial joints and heart valves), they are rarely seen by biomeds. Implantable defibrillators acquire their cardiac information through small wires implanted in appropriate cardiac muscle tissue. Using a proprietary algorithm, these devices constantly analyze the ECG for patterns of ventricular tachycardia or ventricular fibrillation. When the patient exhibits either condition, it delivers an appropriate shock through the same implanted wires. Directly connecting wires to the heart overcomes thoracic impedance, hence requiring much lower voltages to be effective, and allows them to be powered by an internal battery lasting up to 10 years. These devices contain all the basic functionality of an AED—monitoring, a decision-making algorithm, and the circuitry to shock the heart. However, due to their intimate electronic contact with the heart, they can contain these functionalities in a much smaller package. Implantable defibrillators are totally automatic—they determine if the shock is required and then administer it.External manual defibrillators should be considered as resuscitative devices and managed accordingly. Periodic services, such as preventive maintenance, calibration, and electrical safety testing should be individually scheduled, and a detailed maintenance history should be maintained on each supported device. The history should include all scheduled services and both modification and remediation work orders. Maintainers must perform and document all manufacturer- recommended scheduled services. If not specified by the manufacturer, periodic output readings should be taken, since this is one of the more critical aspects of the external manual defibrillator's functions.The location of AEDs should be documented, with scheduled services usually consisting of checking the on-board status indicator on a periodic basis. Many models do not provide any scheduled maintenance or periodic testing procedures and instead rely solely on internal self-testing. Typically, they use a green/red status indicator to indicate “OK/ready/normal” or “malfunctioning.”Since implantable defibrillators are regulated as implants, like stents and prosthetics, rather than as medical equipment, the operating room staff manages these under the same rules, regulations, and facility policies as other implants. After implantation, the cardiologist programs them in a similar manner to pacemaker programming. There is no biomed involvement in this process.No specific regulations cover defibrillators beyond the requirement to conform to the regulations promulgated by the U.S. Food and Drug Administration (FDA) for sale and use of these types of medical devices in the United States. Other authorities, such as the European Community, have similar requirements. However, the U.S. Department of Health and Human Services (HHS) and the General Services Administration (GSA) jointly issued “Guidelines for Public Access Defibrillation Programs in Federal Facilities” in 66 FR 28495–28501. This document became effective on Aug. 14, 2009, and provides information for establishing public access defibrillation (PAD) programs in Federal facilities. Many state, county, and other non-federal activities use this document as a model for their own PAD programs.The International Electrotechnical Commission (IEC) is a worldwide organization for standardization. IEC 60601-2-4:2002 is the international standard for defibrillators. Additionally, the Association for the Advancement of Medical Instrumentation (AAMI) and the American National Standards Institute (formerly the National Bureau of Standards) developed and published ANSI/AAMI DF80:2003/(R)2010, titled “Medical electrical equipment—Part 2-4: Particular requirements for the safety of cardiac defibrillators (including automated external defibrillators).” This standard specifies requirements for the safety of medical electrical equipment intended to defibrillate the heart by an electrical pulse via electrodes applied either to the patient's skin or to the exposed heart and covers some areas not addressed by the IEC standard. These are the two virtually international defibrillator standards followed by all manufacturers.Risk management issues vary with the type of defibrillator. Issues with external manual defibrillators include those related to battery problems, skin burns at the paddle contact sites, and potential fires. Although modern units are designed to operate from a convenience outlet with a shorted or open battery, finding an outlet after encountering a battery failure wastes precious time, decreasing the likelihood of cardioversion. To mitigate this risk, biomed organizations should employ a battery maintenance schedule, which may consist of periodic conditioning, replacement, or both. Both nickel-cadmium (Ni-Cd) and sealed lead acid batteries should generally be replaced after two years of service or when empirical testing indicates a failing battery. Some manufacturers offer other battery types, such as nickel-metal hydride (Ni-MH), lithium-ion (Li-ion), or lithium-manganese (Li-Mn). Facilities should follow both defibrillator and battery manufacturer instructions for their maintenance.Both first- and second-degree burns may occur if insufficient gel is used, if multiple defibrillation attempts are made, or if the paddles are not pressed firmly enough onto the skin. If the paddles are held to the chest with sufficient force (typically 25 pounds of force is sufficient for good contact), then the burns are probably caused by either insufficient or the increased resistance of dried (from repeated cardioversion attempts) gel. To remediate both cases, a generous amount of conductive gel, sufficient to fully and uniformly coat the surfaces of both paddles, should be applied and reapplied after a couple of discharges. Expired self-adhesive or disposable electrodes can leave similar burns on the patient's skin.There also is a small risk of fire coincident with the use of external manual defibrillators. Although rare, these devices have caused bedding fires when patients had been administered supplemental oxygen immediately prior to defibrillator use. All medical staff should be aware of the effect that oxygen has on the ignition temperature of patient gowns, bedding, and disposable drapes in the head and torso area of the defibrillated patient. Even the fine body hairs on the patient can ignite and burn very easily in an oxygen-enriched environment. Staff also should be taught appropriate precautions to prevent an oxygen-fed fire and actions to mitigate the damage should such a fire occur.AEDs can cause the same skin burns as their manual cousins, so those responsible for the PAD program must closely monitor electrode expiration dates and replace them promptly. Likewise, since AEDs employ primary (nonrechargeable) batteries, responsible individuals must ensure the self-monitoring indicator indicates the unit is ready for use. Batteries must be replaced whenever the self-monitoring indicator or the manufacturers' recommended replacement schedule indicates. Models that have a published biomed checkout procedure should have those checks performed in accordance with the manufacturer's published schedule.Since implantable defibrillators are outside the biomed's purview, virtually no clinical engineering risk exists for them. Nevertheless, since they are managed as an implantable appliance, other areas of the facility have risk management issues. However, the primary risks— nosocomial infection and pocket hematoma from the implant surgery—already should be managed by the facility.Historically, the most problematic part of external defibrillators has been the batteries. External manual defibrillators must have their batteries serviced on a regular basis. Depending on the battery type, batteries should be deep-cycled and proactively replaced before the inevitable failures manifest themselves. Implantable defibrillators are managed as disposables. Implanting internal defibrillators protects them from the fluctuations in environmental factors and reduces the power demand that affect other defibrillators. This serves to minimize their failure rate.As previously mentioned, skin burns at the electrode or paddle sites have occurred, especially when multiple countershocks are attempted, but rarely are they the fault of the device. Most investigated occurrences revealed poor skin preparation, dried or insufficient gel, and insufficient pressure on manual paddles to be the most frequent cause of these burns. All of these are within the purview of the operator to prevent or correct.A good general-purpose medical electronics toolkit is mandatory to perform even minimal work on a defibrillator. For performing scheduled services on an external manual defibrillator, a defibrillator analyzer, battery analyzer/reconditioner/charger system, and a safety analyzer coupled with good manufacturer's service literature are necessary. Most modern units require additional test equipment and service aids commensurate with their capabilities. For example, defibrillators with a noninvasive blood pressure (NIBP) module will require the test equipment for testing stand-alone NIBPs. Testing the sync mode without the proper service aids is virtually impossible. Although device-specific training is useful for performing repairs, a skilled biomed possessing general biomed training alone can perform routine scheduled services. The level of additional training and experience needed for repairing these devices depends heavily on the quality of the manufacturer's service literature.The core technology of external manual defibrillators is considered mature. However, the most recent devices now have additional noncardiac-related module options such as 12-lead ECG, end tidal CO2 (ETCO2), and pulse oximetry (SpO2), so that they almost become a patient transport monitor. As they evolve in the future, we will see improvements in both batteries and battery charging technology to improve their reliability.Today's AEDs represent the state-of-the-art for electronic defibrillation devices. They not only analyze and provide countershocks where appropriate, but modern AEDs contain features only dreamt of just a few years ago. Current AEDs also provide audible prompts to aid in performing CPR, document both their own operation and that of the CPR giver, and even record background sound. This is available for downloading to a flash drive or another device via Bluetooth. Future improvements include better software that is not confounded by motion artifact and allows the device to assess the ECG while CPR is in progress. Improved waveform analysis also could lead to better outcomes by determining the optimal time to produce a countershock.Implantable defibrillators have undergone a rapid and significant development during their short history. They detect a number of arrhythmias that are correctable by cardio-version, are able to shock or pace as necessary, and feature extensive programmability and telemetry function. Future units will be smaller, have improved diagnostics thanks to better software, longer battery life, and the ability to handle occurrences of atrial fibrillation.

For many people, the term “robotic surgery” likely evokes one of two images. One is Asimo, the Honda robot, performing a complex heart-valve replacement with the precision and finesse of the most skilled surgeon. The other is more along the lines of an industrial robot found welding on an automotive assembly line—performing surgery by rote programming on scores of patients in a row, just like in a factory. Neither is the case. Robotic surgery is, by some accounts, the next level of minimally invasive surgery.Conventional invasive surgery involves a large incision in the body to gain access to the area and organ of interest. For example, in a conventional gallbladder removal, the surgeon first performs a laparotomy, which is an incision, usually a large one, through the abdominal wall to gain access to the interior of the torso. The problem with a laparotomy is that it is very stressful physiologically and exposes large portions of the patient's abdominal cavity to infection. Additionally, because the incision is so large, and the surgeon needs access to a large part of the patient's interior, the surgery is characterized by a relatively large amount of trauma to the surrounding tissue, blood loss, and postoperative pain and discomfort coupled with a prolonged healing period. To overcome the problems and side effects of the laparotomy, minimally invasive surgery was developed.Minimally invasive surgery accesses the chest or abdomen through several smaller incisions, each one typically half an inch long. Each smaller incision has a port, or a combination trocar/port is used to make the incision, to protect the surrounding tissue while a particular device is inserted through the hole. The most common items inserted are an endoscope connected to a camera, a light source (which may be part of the other devices), an insufflator, and an instrument with one or more operating channels. In the case of minimally invasive gallbladder removal, now called a laparoscopic cholecystectomy, all the associated steps (draining the gall bladder, severing it from the ducts, and removing the empty bladder) are performed through the operating channel using specially adapted instruments. In minimally invasive surgery, as few as three or four small incisions can take the place of the much larger laparotomy incision. Some surgeons also perform this procedure as “scarless surgery” by accessing the abdomen through the navel and using a specialized operating endoscope with integral illumination and operating channels. Although there technically is a scar, observers might be hard pressed to find it as it is hidden in the folds of the navel. As one would expect, the smaller incisions mean less trauma to the body as a whole, reduced blood loss, and minimal discomfort, all of which equate to a shorter healing period.Minimally invasive surgery techniques are primarily responsible for the increase in “same day surgery” procedures. Cases employing laparatomies frequently required a one to two week hospital stay for observation (in the event of complications like hemorrhage) and recuperation. Now that time is reduced to a few hours of post-recovery room rest, and patients are discharged later that same day to finish their recuperation at home.As good as minimally invasive surgery is, it also has some drawbacks. Because the space inside the torso is very limited, and the operation is performed with a minimum of disturbance to the surrounding tissue, it can be difficult for the surgeon to visualize the surgical field and manipulate the instruments. In such a small space, minute but precise movements of the instruments are required to ensure the operation remains trouble free. Poor visibility in the surgical field has led to problems ranging from accidentally nicking adjacent tissue to more serious matters, such as cutting a liver duct in addition to the bile duct or accidentally severing an artery beyond the surgeon's field of view. Robotic surgery systems are designed to overcome these challenges and provide yet another major advancement in surgery. To date, robotic surgery systems are viewed warily in many healthcare facilities, partially due to their high cost—$1.25 million and up—and to the limited types of procedures they may perform. Despite these obstacles, facilities in 2012 performed approximately 450,000 robotic surgical procedures in more than 2,000 facilities worldwide.Robotic surgery systems are expensive, and they are approved by the U.S. Food and Drug Administration (FDA) for only a handful of procedures in cardiac, gynecology, otolaryngology, pediatric, and urology specialties. Second, as of this writing, there are only three models of systems approved for sale and use in the United States, and all of them are made by a single company. Their high price and relatively limited number of approved applications makes them impractical for many small rural medical facilities. They are found more often at tertiary referral facilities, where the necessary specialists and case workload supports their utilization. Because there is only a single manufacturer, much of the information on the three models is considered proprietary. However, some interesting information about them is available if one digs deep enough.All three robotic surgery systems employ a physician's console with computerized controls and a patient side cart containing up to four instrument arms, including an endoscope connected to a fiber optic camera. The surgeon's console is located within several yards of the operating table and patient side cart. Unlike traditional endoscopic viewing, with robotic systems, the surgeon sits and looks into a large hooded viewing area. The hood blocks outside light and facilitates concentration. The high-resolution video monitors inside the hood provide the surgeon a stereo image magnified tenfold of the operating site from the endoscope mounted on the patient side cart. This video system places the surgeon inside the patient looking at the surgical site from only a few millimeters away, with the instruments and images directly in front of the surgeon, between his or her arms. Even current minimally invasive surgery requires the surgeon to look up and away from the patient and his instruments to view the surgical site on a monitor mounted near the operating table. Some surgeons believe that this view is superior to that provided by even conventional surgery. At the surgeon's left and right hands are joystick-like controls with additional controls mounted at his feet. A “bumper” device in the hand controls provides tactile feedback when using certain tissue grasping instruments. Armrests help to minimize fatigue during the operation. The hand and foot controls manipulate the operating instruments attached to the patient side cart. Additionally, the surgeon is capable of zooming in to obtain a better view of details at the surgical site.The computer forms the interface for the surgeon's hand and foot movements and translates those into movements of the instruments attached to the patient side cart. Two important characteristics of the software is that it controls the zoom of the video and reduces the surgeon's movements to compensate for the magnified view of the surgical field. Lastly, the computer buffers the surgeon's movements to compensate for any minor tremors and provides positive feedback to the bumpers when grasping something.The patient side cart replaces the table-side surgeon and looks like a cross between a praying mantis and the multiarmed Hindu goddess Kali. The cart contains as many as four arms, folded like the forelegs of a praying mantis when retracted to the parked position, arrayed across its top to allow full movement of each arm in all planes. Each arm is capable of holding one of the specially designed or adapted operating instruments—a miniaturized surgical camera, wristed scissors, scalpels, forceps—all designed to help with delicate dissection and reconstruction deep inside the body. As the operation progresses, the instruments are changed by the secondary surgeon or by a trained operating room nurse or technician as required.Maintenance services should be scheduled and tracked uniquely for each system with equal consideration given to liability, the initial cost, and the proprietary nature of the hardware and software. Each system should have a detailed maintenance history. Owing to both the uniqueness and proprietary components of robotic surgery systems, a maintenance contract with the manufacturer is recommended. As competitive products enter the field of robotic surgery, options other than full-service contracts may be viable in the future. With manufacturer training, a first-call contract would be the best mix of in-house and contractor maintenance capabilities.There are no specific regulations covering robotic surgery systems. As always, it is crucial to follow regulations promulgated by the FDA.There have been reported equipment malfunctions in robotic surgery systems that impact the risk manager. Malfunctions of the arms, console, the optics, the computer, or any of the instruments during an operation can result in disaster for the patient. The FDA's Manufacturer and User Facility Device Experience (MAUDE) database contains a number of incident reports and complaints about these systems. In 2012, there were 282 adverse event reports associated with these systems at more than 2,000 hospitals. Before allowing surgeons to use robotic surgery systems, hospitals typically require many hours of simulator training, akin to requiring flight simulator and actual flying hours prior to awarding a pilot's rating. Aside from the few computer-related hardware problems, most of the risk management issues associated with these systems are totally in the surgeon's hands. Although tremor-like movements are filtered out, gross unintended hand movements are replicated by the system, which could result in a surgical error. Postoperative infection is always a concern with any invasive procedure, and robotic surgery is no exception. Although the surgery site or sites are smaller, infection either at the point of intrusion or deep within the torso is still a possibility.The most common problems reported with these systems are blown fuses, damaged cannulae, system “lockups,” and operational failure due to software issues. The first two can be can be resolved by in-house biomeds and nursing staff. Rebooting the system can resolve a software lockup, but this can be problematic if a computer lockup occurs repeatedly, especially during a case. Since contract maintenance is recommended, in-house biomeds will rarely if ever be called in to troubleshoot a problem.At this time, no additional training or equipment is necessary to service robotic surgery systems. Because there is only one manufacturer of this product, contract maintenance is the only sensible way to service these systems. As more manufacturers enter the field of robotic surgery, it's possible that service options could well include something other than a full-service contract. When this occurs, a first-call maintenance contract is the method of choice provided manufacturer training is available. Unlike a typical first-call maintenance agreement, such a contract also should cover software and firmware updates. Additionally, it should contain negotiated prices for system upgrades and other options when needed. Although current system designs are proprietary to the sole manufacturer of robotic surgery systems, future systems may employ, in addition to their computer and electronics components, principles of fluidic and vacuum systems to manipulate the arms, hands, and instruments. Biomeds servicing this equipment must be familiar with these systems and generally well versed in all disciplines of biomedical equipment maintenance.While there is only one manufacturer marketing robotic surgery systems in the United States, more are sure to follow. At this time, the field is wide open for improvements. For example, one system currently under development promises to provide both visible light and ultrasound images of the surgical site. This feature will allow the surgeon to see not only the surface, but also the internal structure of the tissue. Another area needing further development is that of tactile feedback. Current units only provide a vibrating indicator of the pressure being exerted. Future instruments may well provide real-time, pressure-proportionate tactile feedback to the surgeon.

In a previous column, I explained that both biological safety cabinets and clean benches are laminar flow hoods, but they have different purposes and very different airflow patterns. Confusing the two can endanger you, coworkers, and possibly even patients. Unlike biological safety cabinets, clean benches provide no protection to personnel or the room in which they are located. Therefore, their usage is limited to applications in which the user is working with nonhazardous substances and in which a clean, particle-free work area is required. Typical nonhospital uses of clean benches include compounding pharmacies, food microbiology, and cell culturing. Outside healthcare facilities, clean benches are used in the semiconductor and aerospace industries, as well as medical device assembly where a pristine product is required.Hospital laboratories may prepare sterile agar plates by decanting a sterilized liquid culture medium into sterile Petri dishes in a clean bench. Pharmacies in large hospitals and medical centers frequently prepare special intravenous (IV) solutions containing medications such as antibiotics or chemotherapy treatments. To prepare these solutions, a specially trained pharmacist or pharmacy technician uses a needle and syringe to aseptically add the prescribed medication to a small (typically 250 mL or less) IV bag. Facilities usually perform these operations inside a clean bench to reduce the possibility of introducing an infectious contaminant during this process. Once the IV bag is delivered to the ward or clinic, a nurse “piggybacks” it to a “keep vein open” (KVO) or “to keep open” (TKO) primary IV.Clean benches provide a stream of air that moves from one end of the cabinet, across the working space, to the opposite side of the cabinet, then into the room in which it is located. Clean benches have two possible airflow patterns: rear to front in horizontal models, or top to bottom in vertical models. The horizontal models, which are the most common type, often have an open front to facilitate airflow and reduce turbulence within the working space. Designs that employ a front cover or panel have provisions to exhaust the air without reducing airflow or compromising the laminar properties of the air by introducing turbulence within the working space.Vertical clean benches typically have a moveable sash on the front to keep the out-flowing air from blowing directly in the user's face. The sash counterbalance system is typically either a cable-and-pulley or a chain-and-sprocket system.Unlike biological safety cabinets, clean benches provide no protection for the user, but almost total protection for the product. This fact should be apparent since the high efficiency particulate air (HEPA) filtered air passes over the product first, then over the user's hands, finally into the user's face or into the room. Therefore, tasks and materials that are infectious or hazardous, such as streaking agar plates or working with flammables, must not be used in a clean bench. The primary purpose for performing tasks in a clean bench is to keep the product clean and sterile—or as close to sterile as possible.Both vertical and horizontal clean benches depend on the unique airflow pattern of HEPA filters to provide the equal airflow speed and parallel flow that is the definition of laminar flow. Unfortunately, using the clean bench by inserting one's hand and arm into the working space will create turbulence that will allow room air to enter it. Manufacturers handle minimizing turbulence in a number of proprietary and patented ways. Typically, both types of cabinets are equipped with one or more air-velocity sensors that alarm when airflow drops too low because of sash positioning or fan failure. As with other laminar flow hoods, clean benches may contain task-specific utilities, such as compressed air or other gases for equipment, electrical outlets, vacuum, as well as the same germicidal ultraviolet lights in the “C” band (UV-C, 280-100 nm).Maintenance services should be scheduled and tracked uniquely for each clean bench. Likewise, the Clinical Engineering or Healthcare Technology Management Department should maintain a specific maintenance history for each device. If maintenance is the responsibility of the Facilities or Engineering departments, that practice should be documented in writing since clean benches are medical devices.In addition to the usual preventive maintenance and electrical safety testing of installed medical equipment, clean benches require periodic performance testing to ensure they meet airflow rate, pattern, and filter integrity specifications. Cabinets that pass these tests are certified, ensuring that they meet the design and required operating parameters. Test frequency varies by country and state, but generally is required annually, usually after the replacement of the HEPA filter. The test equipment, training, and testing aids are very specialized, so if a facility only has a few clean benches, contracting out is usually the most cost effective way of meeting the certification requirement. If the clinical engineering department is responsible for this testing and certification, I strongly recommend considering an annual service contract covering periodic filter repair and replacement as well as certification testing. Normally, clean benches do not require any decontamination prior to performing maintenance; however, a deep cleaning may be required afterward to remove contaminants introduced into the working space by the maintenance action.A number of countries, including the United States, follow the applicable International Organization for Standardization (commonly known as ISO) standard. Clean benches used in the United States are designed to meet ANSI/IEST/ISO 14644-1, which replaced Federal Standard 209E.Although this standard prescribes classifications of the maximum particulate counts by size within the workspace, it leaves the question of how to accomplish this to designers, engineers, and manufacturers.Additionally, chapter 797 of the U.S. Pharmacopeial Convention (USP) contains standards for pharmacies that prepare “compounded sterile preparations.” This category covers both the commercial compounding pharmacies that have been in the news recently, as well as healthcare facility-based pharmaceutical compounding operations, such as IV additive operations. Since The Joint Commission (TJC) has adopted the USP as a whole, compliance with chapter 797 of the USP is required to attain JC accreditation.While none of these standards are regulations in the formal sense, adherence to them will not only provide a safe and clean operating area for the patient, it will also facilitate attainment of the necessary accreditations.Violation of OSHA good manufacturing practices, the ensuing fines, and subjecting patients to potentially fatal bacterial, viral, and fungal contamination are the primary risk management issues. Under Medicare and Medicaid regulations, the expense of treating nosocomial infections is non-reimbursable, so treatment cost must be borne by the facility. This expense far exceeds the cost of proper clean bench maintenance. The risk to facility workers is virtually nonexistent.One often-overlooked risk exists with clean benches that have integral UV C germicidal ultraviolet lights. These lights, while effective in killing bacteria, viruses, and other micro-organisms, can also result in sunburn, skin cancer, corneal inflammation, and retinal damage in humans. Clean benches incorporate safety devices to ensure that the germicidal lights are only on when the bench is closed and not in use.Clean benches are fairly simply devices. The in-house biomed or hospital engineer should be able correct problems typical of these mechanical devices—such as broken fan belts, burnt out motors, and squeaky bearings— with common hand tools. Firms that specialize in clean bench airflow testing, filter replacement, and certification should be employed to perform such work. Although a biomed is capable of replacing the filter, sealing it properly, and then certifying, the clean bench requires some esoteric equipment and training that is often not cost effective for the typical shop. It would be beneficial for an in-house biomed to cultivate a synergistic relationship with the firm testing and certifying the clean bench.Basic biomedical-oriented and electrical-mechanical training, as well as standard hand tools, are necessary for most repairs to clean benches. The certification of clean benches requires several thousand dollars in training, special certification of the worker, and specialized test equipment. The minimum test equipment for testing a clean bench consists of a cold smoke generator, a calibrated anemometer (airflow pressure/rate meter), an aerosol photometer (particle counter), and a calibrated light meter. Typically, this equipment would be used less than eight hours per year, so if certification is to be performed by trained, certified in-house personnel, equipment rental should be considered. Unless a large number of clean benches will be maintained within the facility, it is normally more advantageous to contract this work to a specialty firm.While vertical clean benches are fairly new in the market, the basic design of the horizontal clean bench has not changed significantly over time. Since both vertical and horizontal clean benches rely on HEPA filter technology, their future development is tied unavoidably to those filters. They are considered mature technology, but subject to improvements in the industry. Filters capable of blocking particles as small as 0.12 μm with 99.99% efficiency have recently been adapted for use in older cabinets. Additionally, improvements in components such as electric motors—for example, quieter and more efficient designs—that are introduced into other industries find their way into cabinets as older motors are replaced. The newest designs contain improved acoustical insulation to reduce motor noise and better ergonomics—all in a smaller package.

Our objectives in conducting this evaluation were to present an overview of a basic phacoemulsification system and its components, to describe the phacoemulsification procedure within the context of the operating principles of the system's components, and to compare two manufacturers' products. Specifications for additional phacoemulsification systems are available in the November 1989 edition of ECRI's Hospital Product Comparison System. Both of the evaluated systems enable a surgeon to perform a complete cataract extraction procedure by phacoemulsification. We rated both units Acceptable. In selecting a unit, users should consider performance, safety, human factors design, and manufacturer training and support. Although list prices vary widely among available systems, cost factors should not override clinical performance and safety requirements. While we measured certain engineering parameters, such as stroke length and ultrasound (US) output forces exerted on a medium, we stress that the results of these tests do not provide enough information to predict clinical performance. Clinical performance of phacoemulsification systems can be determined only by the experience of the clinicians who use them. Clinicians should review our evaluation thoroughly before making a purchasing decision. The information we present is useful for purchasing the evaluated or other available models because our criteria will guide users in assessing all components, and our findings and discussion on some aspects are common to many available systems (e.g., type of pump, irrigation and aspiration [I/A] characteristics). The in-depth clinical and technical information will help users to better understand principles, thereby helping them to better define their needs. Although we discovered a number of problems with the evaluated models, users should not assume that similar or other problems do not exist with systems that we did not evaluate. The willingness of manufacturers to cooperate in our studies and the knowledge they gain through participating may lead to the development of better products.

In the purest sense, telemetry is a technology that allows data acquired in one location to be monitored and displayed in another. The word telemetry is formed by combining two Greek words: tele meaning remote and metron meaning measure. Its use is not unique to the medical community. For decades, applications of telemetry ranged from agriculture (soil moisture sensors) to rocketry (monitoring flight parameters) and beyond by remotely measuring radiation in areas inaccessible or hostile to humans. Early telemetry systems used wires, such as dedicated leased telephone lines, or infrared (a point-to-point beam). Today, most telemetry, including medical telemetry, is wireless, using some type of radio frequency (RF) transmitter.Most of today's medical telemetry systems allow clinicians to monitor continuously selected vital signs of patients on intermediate care ("step-down") units as they move around the facility. More dedicated systems are used as part of a cardiac rehabilitation program employing software programs that generate an exercise protocol, then monitor and trend the patient's progress. This allows a much greater exercise range than wired monitor systems, reduces the possibility of lead entanglement as the patient exercises, and prevents artifact pick up by long patient cables. The most common vital sign—and one monitored by all systems—is the electrocardiogram or ECG. Some systems also monitor other physiologic parameters such as the saturation level of oxygen in hemoglobin (pulse oximetry or SpO2), respiration, temperature, noninvasive blood pressure (NIBP), as well as additional derived parameters.Most telemetry systems consist of a battery-powered transmitter carried by the patient—usually in a pocket in the gown, clipped to the gown, or carried in a pouch attached to a harness—and a receiver located at a central monitoring location, typically at the nurse's station of the step-down unit. However, some large hospital systems have established a central facility at one hospital to monitor all patient monitors, both wired and wireless. This remote location, sometimes referred to as a "war room" or "centralized monitoring room," can be miles from the patient, employs CCD cameras and their wide-area network for visual monitoring, and communicates any alarms back to the nursing staff. For engineering and technical reasons, some systems even employ limited two-way communication. That is, they are able to both transmit patient vital signs and receive signals sent from the base or central station unit. Bilateral communication facilitates the ability to employ "frequency hopping spread spectrum" (FHSS) to minimize interference and "direct sequence spread spectrum" (DSSS) transmissions to facilitate data integrity.Every medical telemetry system consists of one or more of the following modules: a patient (yes, in this case the patient is part of the system), preamplifier/modulator electronics and transmitter electronics located in a small case, antenna/antenna network, receiver electronics, display, alarms, and recorder(s). Each module will be discussed generically in this article since designs vary widely by manufacturer.The patient provides the raw input for the preamplifier and related electronics. The ECG signal is taken as a differential signal between a pair of electrodes applied to the patient's body. Small electrodes are placed on the traditional ECG locations on the body. Three different readings may be obtained from three leads. Many systems use just one reading—either lead I, lead II, or lead III— but more sophisticated systems allow multiple leads to be sent to the central station. Additional leads equate to additional readings, up to the typical 10 leads for a diagnostic "12-lead" ECG, although most telemetry systems only employ no more than five leads. The electrodes are connected to lead wires (not to be confused with the term "lead" when referring to standard differential readings) that are in turn connected to a single yoke or patient cable where they run as a single cable from the connector to the preamplifier/modulator electronics contained inside the "telemetry transmitter."The preamplifier takes the differential milli-voltages obtained from the electrodes and increases their potential to obtain usable signals for the modulator electronics. In doing so, the preamplifier also reduces noise and cancels out some interference picked up by the electrodes and lead wires. The modulator electronics attaches the captured signals to, and in some way modulates, a radio frequency signal that is then transmitted through the air. Some modulators simply use the signal to slightly alter the frequency of the transmitted signal (this technique is known in the communications industry as frequency modulation or FM) while others employ digital technology that ranges from the very basic to the very elegant, such as bidirectional, multilead digital packet transmission, and frequency-hopping spread-spectrum transmissions. Some telemetry systems incorporate a button to alert staff when the patient feels something unusual is occurring. This alert is perceived at the central station as an event and may trigger one or more system responses, such as a patient-triggered alarm or hardcopy recording. High-end systems capable of the simultaneous monitoring of multiple ECG leads and other patient parameters usually employ digital electronics and are often referred to simply as "digital" telemetry systems.The transmitter portion is a low-wattage RF transmitter subassembly usually provided by another vendor (specializing in RF devices) and purchased as a single printed circuit board (PCB) or module for attachment to a primary PCB. Other designs incorporate the transmitter components on the main PCB, but the industry is increasingly going to an RF module that is attached to the primary PCB. From a design standpoint, it is fairly straightforward and standardized. The transmitter itself may operate only on a single frequency or be adjusted in the field to operate on one of a limited number of frequencies. In the United States, modern telemetry systems use the Wireless Medical Telemetry Service (WMTS) frequencies of 608–614, 1395–1400, and 1427–1432 MHz, but older systems may still operate on unused television channels (174–216 and 470–668 MHz) or the private land mobile radio band (450–470 MHz) as secondary users. Some digital telemetry systems even employ the facility's wireless local area network (WLAN) operating under the Institute of Electrical and Electronic Engineers (IEEE) 802.11 family of standards. A few telemetry transmitter designs also include small monitors that display the captured heart signals directly on the case of the transmitter module.The antenna system is literally a system within a system. That is, it consists of multiple antennas, strategically placed throughout the facility, wired together in parallel to form a subsystem that receives the signal transmitted by the patient-worn telemetry transmitter. The individual antennas come in two generic types, active and passive. Active antennas contain an integral preamplifier to boost received signal strength while passive antennas depend solely on signal strength to achieve acceptable signal output to the receiver. Due to the low power transmitted, the transmitter-to-antenna range may only be 100 feet or less; therefore, antennas must be strategically placed (ordinarily just inches above or below drop ceilings) in corridors, therapy and recreational areas, and other areas where monitored ambulatory patients may travel or congregate. Some nontherapeutic areas needing antenna placement include the cafeteria, gift shop, and hospital chapel, as well as corridors between those areas and the step-down unit(s). Even systems using the IEEE 802.11 family must plan transceiver placement throughout the WLAN to avoid signal dropouts.The receiver is the companion of the transmitter. The receiver "accepts" the transmitter's signal and converts the modulated data into usable patient ECG signals. The frequency and modulation method must be compatible with the transmitter. Otherwise, the receiver will not provide a usable ECG. Depending on the system design, some receivers can be tuned to match different transmitter frequencies while others use a fixed frequency. Some receivers will be analog and others will be digital. Similarly, the method of demodulation must match the method of modulation and varies from system to system. In all cases, the characteristics of the transmitter and receiver must match; otherwise, data cannot be passed from one to the other. Sometimes, disparate systems are used coincidently in different areas (medical step-down and cardiac rehab, for example) of the hospital. Although both systems may have been designed and installed by the same vendor, and carry the same manufacturer's name, the underlying designs can be so different, especially when their age is several years apart, that transmitters from one will not work correctly or at all with the other system, and vice versa.In facilities that do not employ remote central monitoring, the central station monitor display is the most visible item at the step-down unit's nursing station. This is where the primary human interface takes place and resembles a large television or computer screen. The central station monitor will display up to 16 ECG traces. Additionally, depending on the complexity of the monitoring system, other information ranging from just the patient name on bare-bones systems to nurses-electable multilead ECG displays, SpO2, patient temperature, respiration, NIBP, and even (user-selectable) trending information for the past eight, 24, or more hours, depending on the manufacturer's design, on demand. Some of these complex high-end systems even track the patient throughout the facility using signal triangulation or GPS coordinate information. Typically, there is a personal computer or small server behind this display, multiplexing the signals from the individual receivers into a single video feed for each monitor. The user interfacing consists of a keyboard and mouse or a touchscreen. The monitor display may be monochrome (green or amber on a black background) or multicolored. Multicolored displays are used on higher-end systems and may display current and past alarm information. Virtually the same bells and whistles available on today's wired physiological monitoring systems, such as editing and trending capabilities, are available on telemetry systems if the facility wishes to invest in a high-end digital system.The alarm function—separate from the display—accounts for a major portion of the information provided at the central station console. Alarms can range from the simple (triggering of both audible and visual indications, and storing the types, number, and direction of arrhythmia events) to the complex (ST-segment analysis and alarming when variations beyond selected limits occur). Some systems signal an alarm condition by changing the trace or screen color for that patient and display or flash a message stating the reason for the alarm and add an audible indicator for major alarms. Other systems will indicate an alarm condition and then allow a staff member to respond with the severity of the alarm or even an indication that the situation is normal for this patient. The system then "learns" what constitutes an alarm for this patient and thereafter acts accordingly. Some telemetry systems even employ a hierarchical form of alarm management. When two or more alarm conditions occur simultaneously or near simultaneously, the more serious condition triggers the primary alarm. The other conditions are noted, tracked, and documented. Should the more serious condition be resolved while the other(s) still exist, the alarm is reactivated. Other than some type of audible and visual indicator, the number and types of alarm conditions and indicators vary so widely from system to system that there is no across the board standard.Recorders work in conjunction with the alarms to record the event triggering the alarm. Normally all systems have at least a strip-chart recorder to provide immediate hardcopy documentation of alarm events. This is typically a thermal printer using temperature sensitive, chemically treated paper. The downside of this form of documentation is the relatively short storage time before the image begins to deteriorate. The workaround for this is to photocopy the image to standard paper and store that in the patient record. Better systems typically employ two or more printers. At least one is the traditional strip-chart recorder, while at least one other is an administrative-type laser printer. The laser printer allows the system to print out multilead ECGs and historical information on standard size paper suitable for inclusion in the medical record. High-end systems usually contain two thermal printers, in case one runs out of paper or is busy with another alarming patient, plus the laser printer. Many times, the system contains a built-in time delay, which allows it to print a recording of the patient parameter(s) for some period, typically 30 seconds, before the alarm triggered. This allows the physician to see heart activity (multiple premature ventricular contractions (PVCs), for example) leading up to the alarm event (the arrhythmia that triggered the alarm).Telemetry systems should be managed as a single item, but with component-unique tracking of both scheduled and remedial services. Likewise, a detailed maintenance history should show all services performed, modifications and additions to the system, along with a complete diagram (a blueprint overlay is recommended) showing the exact locations of antennas and line amplifiers in the system.All of the system's components, with the exception of the telemetry transmitter and receiver, are good candidates for in-house maintenance—especially if the telemetry system is similar to or shares components with one or more physiological monitoring system(s) in the facility. Most of the components will be identical or bear a family resemblance to each other. With proper acquisition planning, additional major components (e.g., monitor, printer), as well as modules (e.g., I/O interface boards, power supplies) should be purchased as maintenance "float" items and can be used with both the telemetry and other monitoring systems in the facility. Having these float items immediately available will substantially reduce downtime and overall system maintenance cost.The two items this author recommends be maintained by either the original equipment manufacturer (OEM) or a third-party specialty firm are the telemetry transmitter and receiver. Maintenance of these items requires specialized communications industry expertise, test equipment, and service aids rarely found in a biomed shop. Additionally, the use (utilization rate) of these items is typically so low that investment in them for just the telemetry system is neither warranted nor justified. Out-of-house or one-time contract maintenance is cost-effective for the times when this specialized maintenance is required. A first-call service contract should be considered, especially if RF-component coverage is included.In the United States, the Federal Communications Commission (FCC) has jurisdiction over all aspects of the telemetry transmitters. Old legacy telemetry systems operated as a secondary user on locally unused television channels 7 to 46 (174–216 MHz and 470–668 MHz) and the private land mobile radio portion of the 450–470 MHz band. As several large medical centers learned the hard way, being a secondary user became both costly and dangerous once the FCC began assigning the unused frequencies for digital television service. To address industry concern and to ensure that patient care would not be adversely impacted, the FCC established the WMTS under 47 CFR Part 95H in 2000. The service allocated certain radio frequencies (608–614 MHz, 1395–1400 MHz, and 1427–1432 MHz) to WMTS as a primary user. Unlike traditional radio stations, the language used in Part 95H meant that an individual license is not required to operate the transmitter; it is "licensed by rule." However, Part 95 H also contained a number of restrictions. For example, it restricted WMTS frequency use to authorized healthcare providers (i.e., properly licensed to provide healthcare services). It also called for the designation of a frequency coordinator (the American Society for Healthcare Engineering accepted this role) and the subsequent registration of WMTS devices. Since the transmitter output power must, by law, be less than 1.5 watts and most WMTS transmitters operate within 20 cms of the wearer's body, they are required to meet the RF exposure limits of 47 CFR 2.1093.The most obvious risk management challenge is legacy systems operating on unused television channels and private land mobile radio frequencies. Although it has been 12 years since the establishment of the WMTS, it is possible that, due to economic constraints and questionable management decisions, telemetry systems are still operating outside of the protection afforded by the WMTS.Another is a patient wandering outside of the radio reception area, resulting in a decrease in, then the total loss of, the signal and a lack of monitoring. Just prior to being totally out of range, the ECG signal can be distorted, resulting in an incorrect interpretation and possibly a false arrhythmia alarm.A similar situation occurs when there is a loss of signal strength due to poor antenna placement, loss of an antenna preamplifier, outside interference caused by some other RF-producing device either operating on the same frequency or generating harmonics, cross talk, or heterodyning. Cross talk is especially insidious because it can cause the receiver to capture the signal from a transmitter with which it is not associated. Heterodyning occurs when one radio frequency modulates another slightly different frequency to produce beat frequencies or sidebands. The receiver may perceive these signals as a problematic ECG. Heterodyning commonly occurs when two or more unused active transmitters are stored in close proximity, such as in a drawer at the nurse's station.Manufacturers employ one or more fault tolerant and redundant system designs to mitigate these risks. Examples include WMTS systems employing spread-spectrum and frequency hopping transmitters, bidirectional digital systems that verify each digital packet, and unique transmitter codes programmed into the transmitted signal. Institutions and users can mitigate these issues by careful system selection, controlling RF-producing devices on the grounds of the facility, and always removing the batteries from unused transmitters.The most common problem biomeds encounter with telemetry systems is the dropping of a transmitter. While not appearing to be a biomed issue at first, a transmitter can end up in the biomed's bench for repair—with a piece of white tape stuck to it saying, "doesn't work," without mentioning it was dropped. Upon disassembly, the biomed may find a damaged printed circuit board (PCB) or even droplets inside the case. A damaged PCB can be replaced, but alignment is a challenge since it is rare to find RF alignment equipment in a biomed shop. In such a case, either turning to the OEM or a third-party repair service is recommended. Dealing with droplets is trickier: Are they from pure water, did the patient shower while wearing the transmitter, or was it dropped into a toilet? Often there is no clear answer unless there is a tell-tale smell or visible residue—another good reason to use either OEM or third-party repair.Other common problems with telemetry systems mirror those encountered in conventional bedside monitors, for example, poor electrode-to-skin contact and broken electrode wires. The same resolutions apply to these for telemetry patients as for wired patients. Additionally, loss of transmitter signal will always be a problem since patients are ambulatory and do not always follow prescribed pathways or stay in monitored areas.Except for the RF components (transmitter and receiver), troubleshooting of most of the telemetry system requires the same tools and common test equipment used for wired physiological monitoring systems. Maintenance of telemetry systems requires an experienced biomed, backed up by good service literature (including block diagrams, schematics, circuit descriptions, and installation layout). Model-specific training is not required, but is recommended.Telemetry system technology is considered mature. The only future improvements foreseen are further reductions in size and weight.

Cell washing centrifuges are used in performing blood grouping, typing, compatibility and cross-matching; Rh and antiglobulin (AGT or Coombs) tests; and slide staining. They contain the same basic components as any other centrifuge: the electric motor, the rotor or head, the bowl, and the motor drive electronics. Some cell washing centrifuges also employ the cooling system used in “regular” refrigerated centrifuges. The characteristic that distinguishes a cell washing centrifuge is the special purpose rotor or head fitted to the motor shaft. This head facilitates automatic washing, decanting, mixing, and rewashing of red blood cells. Other ancillary components facilitate the concentration of cells onto slides for microscopic evaluation.Many of the principles outlined in this article also apply to auto-transfusion units—medical devices that connect to a patient, collect specific components of their blood, and reinfuse the remainder plus replacement fluid. At the heart of most auto-transfusion units is a cell separating and washing centrifuge. In a sense, an auto-transfusion unit is the ultimate in semi or fully automatic control of a cell washing centrifuge and its ancillary components.Cell washing begins as any other centrifuge operation: loading test tubes into their holders in the rotor. But unlike normal centrifugation, the caps are removed from the tubes before a lab technician places them into the rotor. Sometimes a separate cover is lowered and secured over the rotor, while other designs incorporate the cover into the lid. A typical wash cycle consists of filling the test tube with saline, centrifuging it, then removal of the supernatant. A subsequent cycle begins by resuspending the sediment in fresh saline solution, usually agitating the tubes, and then repeating the process.Test tubes can be filled two ways: manually by the technician on basic models, or automatically through the use of a container of cell washing solution. That would normally be an IV bag of saline solution and a saline distribution manifold mounted in the cover or on the lid over the rotor on fully automatic models. Once the tubes are filled, they are generally agitated by rapid oscillating rotor movement and then centrifuged to separate the cells from the wash solution, which becomes supernatant. Once the rotor comes to a stop, the bottom of the tubes are held in place or tilted slightly outward, either electromagnetically or by deployment of a mechanical ring, to prevent them from swinging out during the next portion of the cycle. The rotor starts to revolve again at a lower speed, allowing the supernatant to be ejected from the top of the open test tube. Typically the ejected supernatant is caught by the internal cover, allowed to run down the sides of the internal cover, and collected in the bowl or internal trough of the centrifuge. It then exits the centrifuge where it either goes down the drain or is caught by an entrapment system and disposed of in accordance with local environmental laws. This basic cell washing process is used in a number of specialized centrifuges.Cell washing centrifuges performing the direct antiglobulin test generally follow these basic steps using a 0.8% to 0.9% saline solution as the wash. The lab technician prepares a suspension of the patient's red blood cells in a 2% to 5% saline solution in several test tubes, places them in the centrifuge, and initiates the wash cycle. At the appropriate time, either the technician adds antiglobulin, or it is added automatically as part of the cycle. This mixture is agitated and recentrifuged one final time, and the automated cycle ends. The technician removes each tube from the centrifuge and examines the contents for agglutination of the red blood cells. If negative, the technician leaves the tube for about 10 minutes at room temperature, recentrifuges it, and reads it again. A positive reading allows for varying degrees of red blood cell agglutination.Indirect antiblobulin tests are performed in a similar manner, except that the sample serum is first incubated with suspensions of several commercially available reagent red blood cells. The tubes are then placed into the cell washing centrifuge and processed similarly to the direct test. The lab tech then adds antiglobulin serum, recentrifuges the tubes, and checks for agglutination.The cytological centrifuge is an adaptation of the basic cell washing variety, and automatically prepares slides for microscopic examination. The cytological centrifuge uses the outward force generated by the rotation of the head to place cells suspended in a fluid onto microscopic slides. Typically, the lab technician fits together a specimen container, disposable filter card or absorption pad containing two round holes, and a slide. The technician then fills the specimen container. One such assembly is prepared for each slide, and each assembly is placed into a special centrifuge head. The rotor holds the fluid container at an angle away from the filter card while at rest. When rotated, the container tips, driving the fluid into contact with the filter card and glass slide. The outward force of the rotating head creates a layer of cells on one or two small areas of the glass slide over the holes in the filter card. The remainder of the fluid is absorbed by the filter card or absorption pad. The centrifuged slide is then removed from the rotor and fixed using prescribed procedures. If the specimen container is designed for a single use, the entire assembly is discarded. If the specimen container is reusable, the chamber is cleaned and dried; only the filter card and absorption pad are discarded.The rules and management techniques used for general purpose centrifuges apply to the cell washing type as well. It's a good idea for the laboratory to maintain copies of both preventive and remedial service records, as prescribed by its accreditation organization.As is the case with general purpose centrifuges, the College of American Pathologists (CAP), the American Association of Blood Banks (AABB), and The Joint Commission (TJC) certify laboratories and healthcare facilities that employ cell washing centrifuges. Although not regulatory agencies, their certification is necessary for the receipt of federal funding—particularly from Medicare and Medicaid—and seen as a mark of competency, quality, and accuracy. Private sector insurance companies typically follow the lead of the federal government in determining rules for paying providers. Therefore, certification is a virtual requirement for all nonpersonal payments. Maintenance procedures are outlined in the publications available from the various certifying bodies.Of the risks found in general purpose centrifuges, the cell washing type are particularly sensitive to rotational speed, timing, and braking issues. These are key parameters for ensuring proper processing of the cells. The correct speed and timing ensures proper separation between cells and the wash solution. Braking effectiveness ensures the head has come to a complete stop, which is especially important after decanting, before another wash cycle begins. Improper washing and decanting of the supernatant will adversely affect the end product and distort the final results.Additionally, the cell washing centrifuge is designed for only one size of test tube, typically either 10 X 75 mm or 12 X 75 mm. Likewise, the system is designed to use a specific inside diameter of plastic tubing for dispensing the rinsing saline. Using a different inside diameter will change the volume of saline dispensed during the timed filling period. The use of other sizes of test tubes and tubing must be avoided since this will also distort the final results. Lastly, improperly cleaned sample chambers can result in cross-contamination between patient samples and result in false readings.To minimize risks, regular and proper scheduled maintenance of cell washing centrifuges absolutely essential. Additionally, automatic braking must be included in regular preventive maintenance checks to ensure it stops rotating within the allotted time to maintain cycle sequencing. Fortunately, today's centrifuges are relatively maintenance and failure free. As with general purpose centrifuges, their main problem areas are brushes and bearings in the electric motor. Most modern units employ brushless induction motors and long-wearing bearings to minimize their problems.Since a typical cell washing centrifuge is an adaptation of its general purpose cousin in the manufacturer's product line, the training and equipment necessary to service the base—consisting primarily of the motor and control electronics—is the same. The two most important service aids are a tachometer, to determine and confirm that the centrifuge is operating at the correct speed, and a stopwatch to confirm the accuracy of cycle times. The upper portion or bowl components—the rotor, saline distribution manifold, mechanism to hold the bottom of the tubes in place, internal cover or centrifuge lid, the bowl of the centrifuge, and drain—are straightforward items. Likewise, supporting external items such as a saline pump and solenoid valves are generally standard and off the shelf. Manufacturer's literature coupled with common hand tools should take care of most problems with cell washing centrifuges. Manufacturer training would be a plus, although it is not mandatory to service these devices.Cell washing centrifuges employ induction motors, permanently lubricated bearings, and microprocessor technology to control their operating cycles. They are the midpoint between completely manual and fully automated cell processing. Additional improvements on the horizon include multiuse cell washing centrifuges that automatically “sense” which rotor is installed by reading a bar code and accessing an on-board database to set up the processing parameters.Agglutination: the process by which suspended bacteria, cells, or other particles are caused to adhere and form into clumps; similar to precipitation, but the particles are larger and are in suspension rather than being in solution.Antiglobulin: an antibody directed against gamma globulin.Decant: to pour off (wine, for example) without disturbing the sediment or to pour a liquid from one container to another.Supernatant: the soluble liquid portion of a sample after centrifugation or precipitation of insoluble solid matter.

The word chromatography is a combination of two Greek words, chroma (meaning color) and graphein (meaning to write)—the resultant word literally means “color writing.” Chromatography systems are used to separate a complex mixture into its components for further examination or identification. A chromatograph separates components of a mixture by taking advantage of the fact that each component has a different affinity for a particular media. All forms of chromatography use this principle and employ two different media—a sorbent-packed column and a solvent—to separate a mixture into its components. The relative affinity of each component of a mixture to both the stationary phase and the mobile phase causes each component to pass through the column with a unique transit time. This is the basic principle of chromatography. The sorbent-packed column is referred to as the “stationary phase” probably because it does not move. Some of the unknown substance is first mixed with a solvent, called the “mobile phase,” to form a “sample.” This can lead to THE FUNDAMENTALS OF ...

The word chromatography is a combination of two Greek words, chroma (meaning color) and graphein (meaning to write)—the resultant word literally means “color writing.” Chromatography systems are used to separate a complex mixture into its components for further examination or identification. A chromatograph separates components of a mixture by taking advantage of the fact that each component has a different affinity for a particular media. All forms of chromatography use this principle and employ two different media—a sorbent-packed column and a solvent—to separate a mixture into its components. The relative affinity of each component of a mixture to both the stationary phase and the mobile phase causes each component to pass through the column with a unique transit time. This is the basic principle of chromatography. The sorbent-packed column is referred to as the “stationary phase” probably because it does not move. Some of the unknown substance is first mixed with a solvent, called the “mobile phase,” to form a “sample.” This can lead to THE FUNDAMENTALS OF ...

Overview All forms of chromatography separate components of a mixture by taking advantage of the fact that each component has a different affinity for a particular media. Both liquid and gas chromatographs use this principle and employ two different media—a sorbent-packed column and a solvent (termed the stationary phase and the mobile phase)—to separate a mixture into its components. The relative affinity of each component of a mixture, to both the stationary phase and the mobile phase, causes them to pass through the column with a unique transit time. This is the basic principle of chromatography. In “Fundamentals of Liquid Chromatography” (BI&T, July/August 2012), we learned that chromatography systems are used to separate a complex mixture into its components for further examination or identification. The liquid chromatograph performs relatively low-temperature analyses of bodily fluids and is best suited for separating proteins and peptides, measuring toxins, and measuring drug levels in serum for both therapeutic monitoring and unknown drug identification. The gas chromatograph (or GC for short) operates in a comparable manner, performs similar analyses on volatile samples, and does an excellent job of separating mixtures with similar vapor pressures and chemical structures. Gas chromatographs are used to provide fatty acid profiles and blood alcohol determinations. A GC is the only instrument sensitive enough to detect low concentrations of volatile organic mixtures, such as the aromatics (benzene, toluene, xylene, etc.). A GC connected to a mass spectrometer is often referred to as a gas chromatograph-mass spectrometer or GCMS, and is used extensively for performing confirmatory tests for both therapeutic and street drugs. As a general rule, if the sample is not compromised or degraded by the processing temperature, it is suitable for analysis by a GC. Like its cousin the liquid chromatograph, the GC uses both a sorbent-packed column and a solvent. However, since the mobile phase is a gas, the stationary phase can be one of two types. The first is a solid sorbent packed into a tube, similar to that used in liquid chromatography. The other stationary phase employs a solid support with a nonvolatile liquid coating. As is the case in a liquid chromatograph, the relative affinity of each component of a mixture to both the sorbent and the solvent causes each component to exit the column at a particular time after sample injection. Using Kovat’s Retention Index, the retention time of the unknown is compared to retention times stored in a sample library to determine the component(s) of the sample.

The resolution provided by conventional optical microscopes is around 200 nanometers (nm or 10 meters), which is useful to magnify objects up to 2,000 times their size. This is sufficient for examining blood cells, human hairs, postsurgical tissue specimens, most bacteria, and most normal resident and transient flora. However, there exists a world beyond this, which cannot be seen by conventional microscopes. For instances where it is essential to see into this world, electron microscopes are employed. These devices provide resolution down to 50 picometers (pm or 10 meters) and magnifications up to about 10 million. This allows technicians in research laboratories to visualize microorganisms, cells, large molecules, viruses (such H2N2 and the next SARS), and crystals as clearly as blood cells and human hair. Due to their size, cost of acquisition and operation, and plant requirements (such as physical space, electrical power requirements for the components, heating, ventilation, and air conditioning (HVAC) load, dimmable room lighting, utilities), electron microscopes are rarely found outside of research organizations and are rarely used as a diagnostic aid in healthcare facilities. The world of electron microscopes breaks conveniently down into three types—transmission, scanning, and scanning/transmission electron microscopes (which are a combination of both types). They are commonly referred to as TEMs, SEMS, and STEMs. This article will cover TEMs in detail and only touch on the SEM since it is a derivative type. TEMs are the more common type and typically provide better images than either SEMS or STEMs.