OBJECTIVE:Describe reproducibility of a measurement method to investigate deficits in eye-head co-ordination.METHODS:Combined recordings of head and eye rotation using wireless motion sensors and electro-oculography (EOG) were used as an initial step towards a method to quantify eye-head co-ordination deficits. Head rotation to the side during gaze fixation and sequential head and eye movements were studied on 20 asymptomatic control subjects and six subjects with chronic whiplash disorders. All included whiplash subjects reported eye disturbances according to a vision symptom questionnaire.RESULTS:The trial-to-trial reproducibility was moderate to high for 24 of 28 variables (Intraclass Correlation Coefficient 0.44 to 0.87). Velocity gain (ratio of eye and head velocities) was on average close to unity in both groups. Head stability was high in control subjects, while three of six whiplash subjects demonstrated head instability during eye movement. Whiplash subjects also demonstrated a decreased range of head movement during gaze fixation and lower head velocities as compared with the asymptomatics.CONCLUSIONS:The method of combined head and eye motion appears to give accurate, repeatable measurements. Case studies of whiplash subjects indicated deficits in head eye co-ordination. The method could be useful in further clinical research into eye and head movement in those with neck disorders.
In conventional in vivo microscopy, a three dimensional illustration of tissue is lacking. Concerning the microscopic analysis of the pulmonary alveolar network, surgical preparation of the thorax and fixation of the lung is required to place the microscope’s objective. These effects may have influence on the mechanical behaviour of alveoli. Relatively new methods exist for in vivo microscopy being less invasive and enabling an observation without fixation of the lung. The aim of this study was to compare a fibered confocal laser scanning microscopy (FCLSM) with optical coherence tomography (OCT) in a mouse and a rabbit model. Moreover, FCLSM was also used endoscopically in the rabbit model.
This review considers the some of the methods of automatic control which are usable in medicine. The features of each type of control system are explained and the advantages and disadvantages summarised. The author has attempted to maintain a balance between what is possible with the excellence of modern engineering, and what is feasible in the clinical area, and practical when working with patients. The problem of lack of knowledge of an individual patient is emphasised, as is the potential of fuzzy logic methods in the future.
We examined spectral components of beat to beat variability in AC and DC signals of the reflectance photoplethysmograph at finger and earlobe sites in 20 resting volunteers and 20 patients during propofol, alfentanil, isoflurane, nitrous oxide anaesthesia.. We observed that at rest, the majority of spectral power at both sites and in both signals was in the low ‘thermoregulatory’ frequency band (0.01–0.08 Hz). These fluctuations were greater in the finger than in the earlobe and in the AC signal compared to the DC. With anaesthesia, low as well as mid (0.08–0.15 Hz) frequency variability decreased at both sites and in both signals whereas high frequency ‘ventilatory’ power (0.15–0.45 Hz) was maintained. During anaesthesia we found no significant differences between the spectral components of the AC or DC signals or between the finger and the earlobe sites. At all frequencies, the fluctuations in the AC and DC signals were out of phase with each other.
Attempts to quantify the 'Depth of Anesthesia' from EEG have only met with limited success because metric of anesthesia is not uniquely defined.Similarly, many parameters from the EEG have been examined such as Median Frequency, Spectral Edge Frequency, and Power Bands, and none has been found to have universal acceptability.Confounding the application of EEG is the fact that EEG is time varying and differs from region to region in the brain.In most clinical situations, drug dosing is done by choosing a standard dose (eg.EDso or ED9s ), guessing the degree to which a patient is tolerant or sensitive to the drug, and then adjusting the dose by trial and error to avoid toxicity.The drug is most commonly given as a bolus, or in some cases by continuous infusion, and most recently by target-controlled infusion systems that employ pharmacokinetic models derived from population statistics.Recently, several statistically-derived multiparametric indices have been developed, the most successful of which is the Bispectral Index (BIS).BIS has been design to reflect the common sedative effects of anesthetic drugs in a reliable monotonic fashion.The development of this reliable index of level of sedation has allowed the exploration of several automated infusion control strategies.Using the BIS as a feedback control variable, one can either directly control the rate of drug infusion, or the predicted plasma target level can be adjusted in a pharmacokinetic control program such as STANPUMP.While control algorithms as simple as PID have been used, Fuzzy Logic controllers appear to have significant advantages.The application of Artificial Neural Network (ANN) controllers also appears promising, but there has been insufficient training and testing thus far.An Automated BIS Controller (ABC) is in development for the infusion ofPropofol, Methohexital, or ThioPental along with an opiate such as Fentanyl or Alfentanil.Thus far control of the opiate infusion has been without feedback control by front-loading and then either a fixed rate or TCI infusion, but variance in the BIS appears to have useful information for adjusting the opiate infusion and an 'opiate EEG index' similar to BIS can possibly be developed.2. Building a remote control anesthesia information network by a low cost commercial peer to peer system
A PC-based system capable of measuring R-R intervals in the electrocardiogram and detecting respiration phases is presented. It consists of standard amplifiers for ECG and respiration signals and a personal computer that detects QRS complexes, inspiration and expiration using low-pass, high-pass and differentiation processes. The performance of the method is evaluated using an application for real ECG and respiratory data.
Live video and sound from the 11th World Congress of Anaesthesiology in Sydney, Australia were broadcast over the Internet using the CuSeeme software package as part of an ongoing evaluation of Internet-based telecommunication in the delivery of Continuing Medical Education (CME). This was the first time such a broadcast had been attempted from a medical convention. The broadcast lasted for four days, during which a functioning combination of computer hardware and software was established. Technical issues relating to broadcast of these real time signals over ISDN links and the Internet itself were addressed. Over 200 anaesthetists from around the world were able to 'attend' the plenary sessions via the Internet. Evidenced by feedback received audio reception was quite good. Video reception was less successful for those receiving the broadcast via a modem based Internet connection. The received signal in such circumstances was adequate to provide a video presence of the speaker but inadequate to allow details of 35 mm slides to be visualised. We conclude that this technology will be of use in the delivery of CME materials to remote areas provided simultaneous viewing of high resolution still images is possible using another medium, such as the World Wide Web.
Objective. Fast paramagnetic oxygen analyzers have made it possible to measure inspiratory to end-tidal oxygen concentration difference (P(i-et)O2) breath-by-breath. It is now frequently displayed on monitors during routine anesthesia. We wanted to study the effects of major changes in metabolism, ventilation and circulation on P(i-et)O2. Methods. Ten healthy male volunteers were studied under exercise. P(i-et)O2 was measured with a fast-response paramagnetic differential oxygen sensor. Cardiac output was measured with non-invasive transthoracic electrical bioimpedance. Metabolism was measured with indirect calorimetry and ventilation with a side stream spirometer. After a rest period, the subjects cycled at 30W and 60W, 6 minutes on each work load and were then observed during 10 minutes of rest. Results. P(i-et)O2 corresponded well to V̇O2/V̇a (the oxygen uptake to alveolar ventilation quotient) correlation showed r = 0.79. P(i-et)O2 was influenced by changes in cardiac output which occurred primarily at the start and at the end of exercise. Expired minute ventilation (V̇e) multiplied by P(i-et)O2 was related to cardiac output with a high intrapersonal correlation. Conclusion. P(i-et)O2 is a good measure of adequate ventilation in relation to the oxygen consumption level and multiplied by V̇e it might offer a non-invasive bedside parameter indicating changes in cardiac output.
Blood pressure is usually determined by arm sphygmomanometry. However, this technique does not allow continuous blood pressure monitoring. Over the last years, a technique introduced by Peñaz makes it feasible to determine blood pressure noninvasively and continuously from the finger artery. Study on 46 normotensives showed that both methods have high retest-reliabilities for systolic blood pressure while for diastolic blood pressure, arm sphygmomanometry resulted in lower reliabilities than the Peñaz-method. Between-method-comparisons showed only small correlations. Diastolic blood pressure levels were significantly lower in the Peñaz-method than in arm sphygmomanometry. In conclusion, blood pressure levels determined by arm sphygmomanometry and the Peñaz-method differ systematically because of different methodologies. If blood pressure or blood pressure changes are determined, the method and the circumstances of its application need to be carefully reported.
Although auscultation is commonly used as a continuous monitoring tool during anesthesia, the breath sounds of anesthetized patients have never been systematically studied. In this investigation we used digital audio technology to record and analyze the breath sounds of 14 healthy adult patients receiving general anesthesia with positive pressure ventilation. Sounds recorded from inside the esophagus were compared to those recorded from the surface of the chest, and corresponding airflow was measured with a pneumotachograph. The sound samples associated with inspiratory and expiratory phases were analyzed in the time domain (RMS amplitude) and frequency domain (peak frequency, spectral edge, and power ratios). There was a positive linear correlation (R2 > 0.9) between inspiratory flow and sound amplitude in the precordial and esophageal samples of all patients. The RMS amplitude of the inspiratory and expiratory sounds was approximately 13 times greater when recorded from inside the esophagus than from the surface of the chest in all patients at all flows (p < 0.001). The peak frequency (Hz) was significantly higher in the esophageal recordings than the precordial samples (298 +/- 9 vs 181 +/- 10, P < 0.0001), as was the 97% spectral edge (Hz) (740 +/- 7 vs 348 +/- 16, P < 0.0001). In the adult population esophageal stethoscopes yield higher frequencies and greater amplitude than precordial stethoscopes. Quantification of lung sounds may provide for improved monitoring and diagnostic capability during anesthesia and surgery.
OBJECTIVE:Many drugs are known to affect the results of laboratory tests. This may cause problems in the interpretation of clinical laboratory data and lead to wrong diagnoses, unnecessary further tests and additional costs. A computerized monitoring system of potential drug effects on laboratory tests was developed in Turku University Central Hospital. In the present study the incidence and nature of potentially interfering drug effects in thyroid function diagnostics was examined in order to ease the clinical implementation of the system.METHODS:Computerized medication data of 754 hospital in-patients whose thyroid function was tested were combined with a knowledge base of drug effects on laboratory tests. All medications that potentially affected the levels of serum thyrotropin or free thyroxin in study patients were detected.RESULTS:40% (292 of 735) of the patients tested for thyrotropin and 32% (107 of 333) of the patients tested for free thyroxin received potentially interfering medication during the tests. The most common potentially interfering medication was acetylsalicylic acid, but the daily dose was usually low, 100 mg.CONCLUSIONS:The coincidence of potentially interfering medication and thyroid function tests was substantial. On-line hints of drug effects on thyroid function tests might offer valuable decision support to clinicians, but further development of the system is needed to regulate the prevalence of warnings into a clinically optimal level.
Beat-to-beat heart rate variability analysis is a powerful tool for the diagnosis of neuropathy. Respiration-related heart rate variability (respiratory sinus arrhythmia, RSA) reflects the function of parasympathetic nervous system during spontaneous ventilation while awake. RSA is also claimed to monitor the depth of anaesthesia. Power spectrum analysis or various averaging techniques of the heart rate variability are usually applied. The current literature, however, does not usually interpret the ground rules and limitations of the method used, and this may sometimes lead to erroneous conclusions on the data.
The assessment of respiratory system performance may involve issues such as pulmonary gas exchange, respiratory mechanics, oxygen transport and other factors. This paper describes an MS-DOS program called Respiratory Consultant that was designed for use with a hand-held MS-DOS computer, but can also run under Windows 3.1 and Windows 95 if desired. Respiratory Consultant performs a number of computational tasks potentially appropriate to respiratory care in the ICU and elsewhere. These include: predicted arterial oxygen tension from age, interconversion of oxygen tension and saturation, calculation of gas exchange indices and oxygen transport parameters, dead-space estimation, and pulmonary function test interpretation. Respiratory Consultant is freeware that will run easily on most IBM-compatible PCs and may be downloaded from the Internet.
OBJECTIVE:To determine acceptable strategies for automated data acquisition and artifact rejection from computerized ventilators using the Medical Information Bus.DESIGN:Medical practitioners were surveyed to establish 'clinically important' ventilator events. A prospective study involving frequent data collection from ventilators was also conducted.SUBJECTS:Data from 10 adult patients were collected every 10 seconds from a Puritan Bennett 7200A ventilator for a total of 617.1 hours.INTERVENTIONS:Twelve different computerized data selection and artifact algorithms were tested and evaluated.MEASUREMENTS AND MAIN RESULTS:Data derived from 12 data selection algorithms were compared with each other and with data manually charted by respiratory therapists into a computerized charting system. Ventilator setting data collected by the algorithms, such as FIO2, reduced the amount of data collected to about 25% compared to manually charted data. The amount of data collected for measured parameters, such as tidal volume, from the ventilator had large variability and many artifacts. Automated data capture and selection generally increased the amount of data collected compared to manual charting, for example for the 3 minute median the increase was a modest 1.2 times.CONCLUSION:Computerized methods for collecting ventilator setting data were relatively straightforward and more-efficient than manual methods. However, the method for automated selection and presentation of observed measured parameters is much more difficult. Based on the findings and analysis presented here, the authors recommend recording ventilator setting data after they have existed for three minutes and measured parameters using a three minute median data selection strategy. Such an algorithm rejected most artifacts, required minimal computational time, had minimal time-delay, and provided clinically acceptable data acquisition. The results presented here are but a starting point in developing automated ventilator data selection strategies.
We present a computing system for the recording and on-line analysis of analogue signals derived from bedside cerebrovascular monitors in different pathophysiological conditions. These include arterial blood pressure and oxygen saturation, end-tidal carbon dioxide concentration, cerebral blood flow velocities using transcranial Doppler ultrasonography, and concentration changes in cerebral oxy- and deoxyhaemoglobin from near infrared spectroscopy. Configuration and analysis adopts arithmetic expressions of different signal processing functions, various statistical properties for each signal, frequency spectrum analysis using fast Fourier transformation, and correlation/cross-correlation. The software offers off-line analysis of non-invasive tests of cerebrovascular reactivity. Several examples of clinical assessment of cerebrovascular reactivity are presented, including cerebral haemodynamic stress tests which employ carbon dioxide, acetazolamide, the breath holding test, leg cuff inflation and deflation, and transient carotid artery compression. Application within the experimental setting with induced haemorrhagic hypotension can also be used.
Objective: To identify factors which influence the choice of nurses to use automated collection of IV pump data from a prototype Medical Information Bus. Design: Observational study for a duration of three and one-half months. Setting: Four intensive care units, each with different missions, in an adult hospital. Subjects: One hundred fifty-eight registered nurses including both full and part time. Measurements and Main Results: Data were collected from the hospital information system about infusion orders including the type of medication, the number of rate changes, the method of documenting rate changes and the infusion methods. The method of documentation for infusion rate changes was defined as either automated, using a prototype Medical Information Bus (MIB), or manual, using the keyboard at a bedside computer terminal. The method of infusion was defined as either straight gravity feed without an IV pump (‘no pump’), infusion using a pump but without connection to the hospital information system (‘pump only’) and infusion using a pump which was connected to the hospital information system using a prototype Medical Information Bus (‘automated’). A total of 22,199 rate changes were documented during the study period and of those, 22,055 (99.35%) used the ‘automated’ method. Medications with the highest average rate change per single container were; Nitroprusside Sodium (9.50), Epinephrine (9.08) and Epoprostenol (7.50). Conclusions: The nurses used automated IV pump data acquisition with medications which required frequent rate changes.
