Objective: Accurate total hemoglobin concentration (ctHb) measurement is critical for clinical decision-making, particularly in acute care, where immediate therapeutic decisions are required. This study evaluated previously established laboratory-based accuracy criteria for ctHb measurements in routine clinical practice at an interdisciplinary operative intensive care unit (IO-ICU), and with particular attention to significantly reduced hemoglobin concentrations. Method: Remaining blood from blood gas analysis (BGA) cuvettes was collected directly at the ICU bedside. From these initial samples, three clinically relevant measurement scenarios were established: direct bedside measurement (Group 01), elevated ctHb levels (Group 02), and lowered ctHb concentrations below 9 g/dl (Group 03). The samples were analyzed using the GEM 4000, GEM 5000 (Werfen GmbH, Muenchen, Germany), ABL90 Flex plus (Radiometer GmbH, Krefeld, Germany), HemoCue Hb 201+, and XN 9000/9100 (Sysmex Deutschland GmbH, Norderstedt, Germany) automatic hematology analyzers. Since each measurement device inherently possesses systematic deviations, no single analyzer was defined as an absolute reference. Instead, the mean value across all tested measurement systems was utilized as a best-fit reference (REF) value. Results: A total of 120 data pairs from 40 ICU patients were analyzed using regression analyses, Bland and Altman (B&A) methods, and tolerance level analysis (TLA). The results demonstrated strong concordance among the evaluated measurement devices across the examined ctHb spectrum (~1–18 g/dL). Moderate systematic deviations identified by B&A analysis were most pronounced at critically low ctHb levels (<6 g/dL). A key outcome was the determination of 95% prediction intervals (PIs), representing a quantifiable range of uncertainties for future bedside measurements. The PIs for Group 03 “low” were in the range of ±7% (relative difference) or ±0.38 g/dL (absolute difference). Conclusion: This study effectively translates previous laboratory findings into clinical practice, highlighting the practical utility of PIs to guide the accurate interpretation of bedside ctHb measurements under acute care conditions.

Background: Tumescent local anaesthesia with prilocain can lead to clinically significant methemoglobin levels. New generation multiple wavelength pulse oximeters (e. g. Masimo Radical 7®) can measure methemoglobin levels. Methods: In this prospective observational study we compared the venous methemoglobin levels and the corresponding pulse oximetric values of the Radical 7® in patients undergoing tumescent local anaesthesia for liposuction procedures. The measurements were performed in Hanseklinik, Luebeck, Germany between 2008 and 2011. Results: In 133 patients, we measured a maximum methemoglobin level of 18 per cent. In a Bland-Altman analysis we found a mean bias of +2.2 % (-4.1 to 8.4 limits of agreement) for pulse oximetric values compared to hemoximetry. Conclusion: Pulse oximetric measurement of methemoglobin is an early-warning tool for the detection of clinically significant methaemoglobinemia in patients with tumescent local anaesthesia.

Objective: The main objective of this investigation is to provide data about the accuracy of total hemoglobin concentration measurements with respect to clinical settings, and to devices within the categories of point-of-care and reference systems. In particular, tolerance of hemoglobin concentrations below 9 g/dL that have become common in clinical practice today determines the need to demonstrate the limits of measurement accuracy in patient care. Methods: Samples extracted from six units of heparinized human blood with total hemoglobin concentrations ranging from 3 to 18 g/dL were assigned to the test devices in a random order. The pool of test devices comprised blood gas analyzers, an automatic hematology analyzer, a laboratory reference method, and the point-of-care system HemoCue. To reduce the pre-analytic error, each sample was measured three times. Due to the characteristics of the tested devices and methods, we selected the mean values of the data from all these devices, measured at the corresponding total hemoglobin concentrations, as the reference. Main results: The measurement results of the test devices overlap within strict limits (R2 = 0.999). Only the detailed analysis provides information about minor but systematic deviations. In the group of clinically relevant devices, which are involved in patient blood management decisions, the relative differences were within the limit of +/− 5 % for values down to 3 g/dL. Conclusions: A clinically relevant change of +/− 0.5 g/dL of total hemoglobin concentration can be detected with all selected devices and methods. Compliance with more stringent definitions—these are the relative differences of 5 % in relation to the corresponding reference values and the clinically adapted thresholds in the format of a tolerance level analysis—was achieved by the clinical devices assessed here.

Objective: Due to ongoing technical progress, the ultrasonic measurement of blood pressure (BP) as an alternative to oscillometric measurement (NIBP) or the continuous non-invasive arterial pressure method (CNAP) moves further into focus. The US method offers several advantages over NIBP and CNAP, such as deep tissue penetration and the utilization of different arterial locations. Approach: Ten healthy subjects (six female, aged 30.9 ± 4.6 years) volunteered in our investigation. In the ultrasonic BP measurement, we differentiated between the directly measured (pulsatile diastolic and systolic vessel diameter) and indirectly calculated variables at three different artery locations on both arms, with two different ultrasound devices in the transversal and longitudinal directions of the transducer. Simultaneously, NIBP monitoring served as reference BP, while CNAP monitored the steady state condition of the arm under investigation. The Moens–Korteweg algorithm (MKE) and the algorithm of the working group of San Diego (SanD) were selected for the indirectly calculated ultrasonic BP data. Main results: With US, we were able to measure the BP at each selected arterial position. Due to the investigation setup, we found small but significant interactions of the main effects. Bland and Altman analysis revealed that US-BP measurement was similar to NIBP, with superior accuracy when compared to the established CNAP method. In addition, US-BP measurement showed that the measurement accuracy of both arms can be regarded as identical. In a detailed comparison of the selected arterial vascular sections, systematic discrepancies between the right and left arm could be observed. Conclusion: In our pilot study, we measured BP effectively and accurately by US using two different devices. Our findings suggest that ultrasonic BP measurement is an adequate alternative for live and continuous hemodynamic monitoring.

The measurement and analysis of the arterial pulse wave provides information about the state of vascular health. When measuring blood pressure according to Riva-Rocci, the systolic and diastolic blood pressure is measured non-invasively with an inflatable pressure cuff on the upper arm. Today's blood pressure monitors analyze the pulse wave in reference to the rising or falling cuff pressure. With the help of additional pulse wave analysis, one can determine the pulse rate and the heart rate variability. In this paper, we investigated the concept, the construction, and the limitations of ultrawideband (UWB) radar and continuous wave (CW) radar, which provide continuous and non-invasive pulse wave measurements. We integrated the sensors into a complete measurement system. We measured the pulse wave of the cuff pressure, the radar sensor (both UWB and CW), the optical sensor, and ultrasonic Doppler as a reference. We discussed the results and the sensor characteristics. The main conclusion was that the resolution of the pulse radar was too low, even with a maximum bandwidth of 10 GHz, to measure pulse waves reliably. The continuous wave radar provides promising results for a phantom if adjusted properly with phase shifts and frequency. In the future, we intend to develop a CW radar solution with frequency adaption.

Intralipid emulsion is often used as optical model substance to mimick living tissue’s strong scattering properties. As such it is of considerable importance to utilize realistic parameters for any type of simulation or calculation in context of Near Infrared Spectroscopy. We determined optical properties of diluted Intralipid solutions at often used, realistic volume concentrations ρ il and at two NIRS wavelengths (780nm and 850nm) in a double integrating Ulbricht–sphere setup. The results were used in Monte Carlo (MC) simulations of an experiment, described in our companion paper. Both, phantom experiments and MC simulation showed qualitatively similar results and demonstrated the effects of changing the three major NIRS factors, namely the penetrated layer depth (d), the Intralipid concentration ρ il and the source–detector separation (SDS). The results demonstrated that light reaching the detectors was inversely proportional to ρ il and d. It also showed that very low Intralipid concentrations do not follow the optical properties documented for Intralipid 20%.

Intralipid emulsion is often used as optical model substance to mimic living tissue’s strong scattering properties. As such it is of considerable importance to utilize realistic parameters for any type of simulation or calculation in context of Near Infrared Spectroscopy. We determined optical characteristics of diluted Intralipid solutions at often used, realistic volume concentrations ρil and at two wavelengths (780nm and 850nm) in a simple phantom setup featuring multiple sensors with different source-detector-separation (SDS) and penetration depths d. Both, phantom experiments and MC simulation showed qualitatively similar results and demonstrated the influence of the three major NIRS factors, namely the penetrated layer depth (d), the Intralipid concentration ρil and the source–detector separation (SDS). The results demonstrated that light reaching the detectors is inversely proportional to ρil and d. It corroborates the need for differential measurements with at least two SDS to account for superficial large angle scattering.

In this review, scientific investigations of point-of-care testing (POCT) and point-of-care monitoring (POCM) devices are summarized with regard to the measurement accuracy of the hemoglobin concentration. As a common basis, information according to the Bland and Altman principle [bias, limits of agreement (LOA)] as well as the measurement accuracy and precision are considered, so that the comparability can be mapped. These collected data are subdivided according to the manufacturers, devices and procedures (invasive and non-invasive). A total of 31 devices were identified. A comparability of the scientific investigations in particular was given for 23 devices (18 invasive and five non-invasive measuring devices). In terms of measurement accuracy, there is a clear leap between invasive and non-invasive procedures, while no discernible improvement can be derived in the considered time frame from 2010 to 2018. According to the intended use, strict specifications result from the clinical standards, which are insufficiently met by the systems. More stringent requirements can be derived both in the area of blood donation and in the treatment of patients.

Die Begriffe E‑Health und Digitalisierung sind Kernelemente eines Wandels unserer Zeit. Wesentliche Treiber dieses Wandels sind – neben einem dynamischen Markt – die gravierenden Vorteile für das Gesundheitswesen in der Bearbeitung von Aufgaben und Anforderungen. Das Aufkommen großer Datenmengen, das rapide wachsende medizinische Wissen, die rasch fortschreitenden technologischen Entwicklungen und das Ziel einer personalisierten individuell angepassten Therapie für den Patienten machen den Einsatz zwingend notwendig. Während E‑Health den Einsatz von Informations- und Kommunikationstechnologien im Gesundheitswesen beschreibt, sind dem Begriff der Digitalisierung die zugrundeliegenden Prozesse der Veränderungen und Innovationen zugeordnet. Digitale Technologien umfassen Software- und Hardware-basierte Entwicklungen. Unter dem Begriff „klinische Datenintelligenz“ werden Eigenschaften hinsichtlich der Leistungsfähigkeit und der Zusammenarbeit klinisch relevanter Systeme charakterisiert. Die Hierarchie in der digitalen Bearbeitung bildet Ebenen von der reinen Datenverwaltung über klinische Entscheidungsunterstützung bis zu automatisierten Prozessabläufen und autonom agierenden Einheiten ab. Die Kombination aus Patientendatenmanagement und klinischer Entscheidungsunterstützung beweist hierbei ihren Stellenwert in Bezug auf Fehlervermeidung, Prävention, Qualität und Sicherheit, insbesondere bei der Arzneimitteltherapie. Ziel dieser Übersicht ist die Darstellung der bereits bestehenden Realität in der Klinik mit den daraus abzuleitenden Perspektiven aus der Sicht des medizinischen Anwenders.

In the noninvasive determination of the hemoglobin concentration the main challenge is the "optical path".With sensors -fixed on human skin -the optical path cannot be exactly determined, as it is defined as the layer thickness in the Lambert Beer principle.The layer thickness is significantly involved in the optical interactions in the tissue.To circumvent this problem self-learning algorithms were evaluated which provide the hemoglobin concentration from reflection and transmission data without knowledge of the layer thickness.First various regression models were trained based on an high rate data set.To evaluate the six most promising models, a prediction dataset was measured in a prospective randomized and blinded study to guarantee integrity of the results.For both data sets, the transmission and reflection of diluted heparinized erythrocyte concentrate was determined with a double integrating sphere setup (laser diodes with 780 to 1310 nm).The evaluated hemoglobin concentrations ranged from 4 to 16 g/dl at a constant oxygen saturation above 97 %.Optical flow through cuvettes (1, 2, 3 mm) simulated different layer thicknesses of the blood.The evaluation of the predictions yielded that the layer thickness independent prediction of the hemoglobin concentration is feasible with the selected approaches.The mean absolute error (MAE) of the best regression model (GPRM -Matern 5/2) is 0.79 g/dl.In the clinically relevant tHb range of less than 8 g/dl the MAE was as low as 0.52 g/dl.

The interest of this paper is the determination of the optical properties of oxygenated (saturation above 97 %) hemoglobin in clinical relevant concentrations (ranging from 5 to 15 g/dl), dependent on the layer thickness. Furthermore the generation of a high rate data set for training with machine learning approaches was intended. With a double integrating sphere setup (laser diodes from 780 to 1310 nm) - as a well referenced method - and flow through optical cuvettes ranging from 1 to 3 mm layer thickness, the transmission (𝑀𝑇) and reflection (𝑀𝑅) values of the samples were acquired. From those the layer thickness independent absorption (𝜇𝑎) and reduced scattering coefficients (𝜇𝑠’) were calculated by the means of the Inverse Adding Doubling (IAD) algorithm. For each sample the same coefficients should result correspondingly for all cuvette thicknesses in test. This relationship serves as an internal standard in the evaluation of the collected data sets. In parallel a spectrophotometer in the range from 690 to 1000 nm recorded transmission spectra for all samples as a second reference. First, the IAD algorithm provided optical coefficients (𝜇𝑎, 𝜇𝑠’) in all measurements, with few exceptions at low hemoglobin concentrations. The resulting coefficients match independently of the layer thickness. As a main second result, a high rate data set was generated which serves for further analysis - for example with machine learning approaches.

In the noninvasive determination of the hemoglobin concentration a main challenge is the "optical path". With sensors - fixed on human skin - the optical path cannot be exactly determined, as it is defined as the layer thickness in the Lambert Beer principle. The layer thickness is significantly involved in the optical interactions in the tissue. To circumvent this problem self-learning algorithms were evaluated which provide the hemoglobin concentration from reflection and transmission data without knowledge of the layer thickness. First various regression models were trained based on an high rate data set. To evaluate the six most promising models, a prediction dataset was measured in a prospective randomized and blinded study to guarantee integrity of the results. For both data sets, the transmission and reflection of diluted heparinized erythrocyte concentrate was determined with a double integrating sphere setup (laser diodes with 780 to 1310 nm). The evaluated hemoglobin concentrations ranged from 4 to 16 g/dl at a constant oxygen saturation above 97 %. Optical flow through cuvettes (1, 2, 3 mm) simulated different layer thicknesses of the blood. The evaluation of the predictions yielded that the layer thickness independent prediction of the hemoglobin concentration is feasible with the selected approaches. The mean absolute error (MAE) of the best regression model (GPRM - Matern 5/2) is 0.79 g/dl. In the clinically relevant tHb range of less than 8 g/dl the MAE was as low as 0.52 g/dl.

The development of an optical sensor for non-invasive measurements in humans requires a test setup, where the optical properties of tissue and blood can be adjusted and measured standardized. The goal of this work is to develop a simplified device based on an integrating sphere setup to evaluate the optical properties of tissue and blood phantoms with respect to static as well as flow conditions. Furthermore, the measurement system is intended to be used at different locations such as laboratories and operating theaters. We evaluate the absorption μa and reduced scattering μs' coefficients of specimens, with the developed integrating sphere setup. The measurement is regulated by a microcontroller for averaging and processing the data. The system is housed in a lightproof box and powered by a battery and therefore transportable. Due to this construction, no calibration is necessary between transports of the system. Calculations are executed with the inverse adding doubling algorithm. In order to basically calibrate and evaluate the setup before first transportation, a dilution series with Intralipid and India ink serve for the test. The results were consistent with precedent studies (mean absolute deviation for μs' of 0.75 mm-1) and demonstrate that this method might be able to produce liquids with adjustable optical properties, as required for further research. Furthermore, a first dilution series of heparinized heamoglobin (5 to 15 g/dl) with oxygen saturation of 98 % was measured with this system under flow conditions.

Anaesthesia in ‘remote areas’ is required for medical imaging (CT, MRI, PET-CT), angiography, endoscopy, and interventions (stenting, thrombectomy, coiling, laser therapy, biopsies, radiotherapy) in a number of medical disciplines (paediatrics, radiology, cardiology, pulmonology, gastroenterology, surgery, cardiac surgery, emergency medicine). The spectrum of anaesthetic techniques is broad. It reaches from standby (monitored anaesthesia care), through analgesia and sedation (with spontaneous breathing), to general anaesthesia and mechanical ventilation. Regional anaesthesia techniques are also required under certain circumstances. In the last few years there has been a move away from open procedures to interventional techniques. The complexity of these interventions has increased (i.e. interventional cardiac valve replacements) and the patients tend to be older and suffer from a multitude of co-morbidities. Many of these interventions are performed in the ‘hostile environment’ of the intervention suite. Intervention suites are typically not designed to offer anaesthetists an ideal working area. The space may be limited and medical equipment impedes access to the patient. The infrastructure may be suboptimal (e.g. no central medical gases supply). Protection for staff and equipment against radiation and high magnetic fields must be considered. Loud noise from machinery and shielded walls, doors, and windows may hinder communication and hearing acoustic alarms. The distance to the operating theatre may be considerable and thus support from senior anaesthetists and supply of additional equipment may take some time to arrive. Anaesthesia outside the operating theatre is sometimes underestimated as trivial. Performing a ‘quick’ interventional case can evolve within seconds into a challenge even for the experienced anaesthesiologist if a surgical or anaesthesiological complication occurs. Non-operating-theatre anaesthesia has a higher severity of injuries and more substandard care than operating theatre anaesthesia. This is not acceptable and anaesthetists must ensure the same high standard of anaesthesia care and patient safety both inside and outside the operating theatre.

The combination of an oxidant source, ignition energy and flammable material is the reason for fire, burning and explosion (FBE) in the OR. Attending anaesthesiologists face these risks in their daily routine. Mostly, a situation with FBE arises in an unexpected situation. It is essential to have at hand a catalogue of measures to prevent severe injuries to patients and avoid material damages. There is a systematic way to decrease the risk: awareness and definition of high-risk situations; team work; building up a strategy to avoid the occurrence of fire, burning and explosion in high-risk situations. The risk profile should be part of security checklists. If there is physical injury caused by fire in the OR, the extent of trauma must be assessed and documented. Finally, an interdisciplinary review may be indicated. Institutional standards regarding risk- and quality management, e. g. working place orders and measures of fire prevention, increase patient security. Systematic implementation of measures and annual training sessions are indispensable.

Ultra-wideband signals have a variety of applications. An upcoming medical application is the detection of the heart rate of patients. However, current UWB systems provide poor resolution and are only able to detect vessels with a large diameter, e.g. the aorta. The detection and quantification of vascular dilation of thinner vessels is essential to develop wearable ultra-wideband based devices for real-time detection of cardiovascular conditions of the extremities. The reflection and transmission processes of those signals within inhomogeneous bodies are complex and their prediction is challenging. In this paper, we present an experimental setup (UWB system; phantom) for the detection of vascular dilation within soft tissues. Furthermore, we suggest a theoretical simulation model for the prediction of the reflection of ultra-wideband pulses and compare these simulated predictions to results of measurements within the phantom. The results verify that we are able to identify vascular dilation within the simulation model and the experimental setup, depending on the depth of the vessel (20 mm, 40 mm, 60 mm).

The venous oxygen saturation reflects pathophysiological changes in oxygen delivery and consumption, where the saturation range beneath 50% may represent a clinical borderline to avoid irreversible damage. We present a model to simulate a desaturation investigation with 4 plateaus (PL1 = 99 ± 0.3%; PL2 = 75 ± 3%; PL3 = 50 ± 3%, PL4 = 25 ± 3%). A continuous wave multi-distance near-infrared spectroscopy sensor (wavelengths: 770, 808 and 850 nm; 6 photodiodes (PD1−6), linearly arranged, separated 6 mm each) was equipped to detect the saturation at these plateaus. The study was divided in 5 calibration experiments (1 day; 5 per day) and 25 experiments (5 days; 5 per day) with the calibrated sensor unit. The detected saturation was compared with the reference values from the CO-Oximetry unit (IL-682) while keeping the amount of total hemoglobin (tHb) and the other physiological parameters at constant levels (tHb = 12 ± 0.3 g dl−1, blood temperature = 35.5 ± 0.6 °C, carbon dioxide partial pressure (pCO2) = 39 ± 6 mmHg, glucose = 103 ± 9 mg dl−1 and pH 7.4 ± 0.04). The oxygen saturation, in the range from 99% to 20%, could be detected reproducible with a mean absolute deviation of 3%.

The oxygenation, perfusion and metabolism of the brain—segmented in both hemispheres—can be estimated from the oxygenation and hemoglobin levels of the venous blood in the cerebral efferent vessels. We present a phantom based model to simulate the anatomical target region which was connected to hemodynamic perfusion circuit to provide different oxygenation plateaus inside of the simulated target vessel. A developed triple-wavelength (770, 808 and 850 nm) multi-distance near-infrared spectroscopy sensor (6 photodiodes (PD1–6), linearly arranged, separated 6 mm each) was equipped to detect these different saturation levels. The saturation could be triggered to three consecutively passed plateaus (PL1 = 55 ± 3%; PL2 = 100 ± 0.3%; PL3 = 55 ± 3%) for all 90 experiments (30 measurements per wavelength (3 d; 10 d−1)) while keeping the amount of total hemoglobin (tHb) and the other physiological blood parameters at constant levels (tHb = 11.8 ± 0.2 g dl−1, blood temperature = 35.5 ± 0.5 °C, carbon dioxide partial pressure (pCO2) = 44 ± 6 mmHg, Glucose = 99 ± 8 mg dl−1 and pH 7.35 ± 0.04). The saturation plateaus inside of the target vessel could be detected reproducibly with the presented setup.

Wireless medical sensors are an emerging technology. Wireless sensors form networks and are placed in an unknown environment. For indoor scenarios context detection of medical sensors, e.g. removal of sensors from a specific room, is important. Current algorithms for context detection of wireless sensors are based on RF signals, but RF signal propagation and room location show only a weak correlation. Recent approaches with RSSI-measurements are based on prior fingerprinting and therefore costly. In our approach, we equip wireless sensor nodes with a barometric sensor to measure pressure disturbances that occur, when doors of rooms are opened or closed. By signal processing of these disturbances our proposed algorithm detects rooms and estimates distances without prior knowledge in an unknown environment. Based on these measurement we automatically build a topology graph representing the room context and distances for indoor environment in a model for buildings. We evaluate our algorithm within a wireless sensor network and show the performance of our solution.

Electrochemical sensors are used in various gas measurement applications and are available for different gases. Depending on the application, the sensor might need to be installed far away from the actual measurement site, requiring the use of long sampling lines. Examples are portable gas measurement devices in which remote locations like tanks and chemical reactors need to be monitored. But also medical applications, where the sensors cannot be positioned in close vicinity to the patient, are common like, e.g., the side-stream measurement of breathing gas. Due to the characteristics of electrochemical sensors and to the adsorption and desorption behavior of sampling lines for different gases, the electrical sensor signal may indicate long response times. In this paper, we propose an on-line signal processing algorithm which is capable to significantly improve the performance. After characterizing the dynamic behavior of the sensor system, a properly designed deconvolution filter is used to reduce response time and signal noise. Within this article, we also provide an example of this algorithm for a novel electrochemical sensor for the measurement of the anesthetic agent propofol in exhaled air. For this application, the acceleration is prerequisite for the measurement chain to be of practical use in a clinical setting. Our goals, to establish measurement dynamics to record the physiologic parameter and to reduce non-physiological disturbances, were achieved with additional reserves. This article is based on 1 and is extended by original clinical data. As an example, we present propofol monitoring in breath of one patient in order to demonstrate the performance of the introduced algorithm in a real clinical application. We proved that the electrochemical sensor, associated with the provided algorithm, is capable for real-time monitoring in a clinical setting.