In Vivo Evaluation of a Mechanical Ventilator Prototype

Home , Leipzig University, University of Freiburg

Biomed Tech 2016; 61 (s90) © by Walter de Gruyter • Berlin • Boston. DOI 10.1515/bmt-2016-5008 S90

ID: J-OP-02

Ventilation with “Expiratory Ventilation Assistance” – In vivo evaluation of a mechanical ventilator prototype

Johannes Schmidt, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Christin Wenzel, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Marlene Mahn, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Sashko Spassov, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Heidi Cristina-Schmitz, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Silke Borgmann, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Jörg Haberstroh, Experimental Surgery, Center for Experimental Models and Transgenic Service, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Stephan Meckel, Department of Neuroradiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Steffen Wirth, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] Stefan Schumann, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected]

Emergency access to the airway with small bore catheters is commonly accepted. However, ventilation is limited by insufficient expiratory flow due to the generated high airway resistance. In a controlled in-vivo trial we evaluate a new automatic mechanical ventilator with an “Expiratory Ventilation Assistance” (EVA) via a cuffed endotracheal tube having an inner diameter of 2 mm. This allows a fully controlled ventilation, i.e. flow controlled inspiration and active expiration induced by suctioning. Anesthetised pigs (40-51 kg, 7 per group) were either ventilated with a conventional ventilator (Evita 4, Dräger Medical, Lübeck, Germany; = control group) or the mechanical EVA-ventilator prototype (Ventinova Medical BV, Eindhoven, The Netherlands; = EVA group) for five hours. Respiratory parameters, arterial blood gases (ABG) and hemodynamic markers were recorded hourly. After five hours a computed tomography (CT) of the thorax was performed. For statistical analyses the Welch’s t-test was performed. The EVA-ventilator achieved a minute volume up to 6.2 l/min. Mean airway pressure was significantly higher in the EVA group compared to the control group (12.0 ± 0.6 mbar vs. 8.9 ± 0.2 mbar, p=0.0007). Arterial O2 partial pressure was significantly higher in the EVA-group (142.6 ± 5.6 mmHg vs. 130.7 ± 3.1 mmHg, p=0.006). Despite a significantly lower minute volume in the EVA group (5.5 ± 0.4 l/min vs. 6.7 ± 0.9 l/min, p=0.04), arterial CO2 partial pressure was comparable in both groups (41.3 ± 1.6 mmHg vs. 41.5 ± 1.2 mmHg, p=0.83). Mean arterial pressure was significantly lower in the EVA group (71 ± 9 mmHg vs. 89 ± 9 mmHg, p=0.02). The CT revealed a more constant and steady distribution of ventilation during a breathing cycle in the EVA group. Our results suggest that gas exchange is improved due to increased alveolar ventilation with EVA.

Biomed Tech 2016; 61 (s91) © by Walter de Gruyter • Berlin • Boston. DOI 10.1515/bmt-2016-5008 S91

ID: J-OP-03

Pressure-flow characteristics of coaxial tubing systems

C. Wenzel, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] S. Schumann, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected] J. Spaeth, Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, [email protected]

During mechanical ventilation, tubing systems represent an essential component of the artificial airways. Conventional, a circular tubing system comprises two separate tubes one for inspiration and one for expiration, a Y-piece and a 90°- connector. Since recently, coaxial tubing systems (coaxTS) are available. These coaxTS include the inspiratory tube within the expiratory tube’s lumen. By design, this facilitates clinical handling. However, the cross section areas of the inspiratory and expiratory tubes are reduced, which may impact resistance to airflow. We hypothesized that coaxTS increase resistance to airflow and related work of breathing (WOB) compared to conventional tubing systems. Therefore, we determined the flow-dependent pressure gradient (∆P) across a conventional reusable tubing system (crTS; composed of two silicone tubes, Y-piece and 90°-connector), a conventional disposable tubing system (cdTS; composed of two plastic tubes, Y-piece and 90°-connector) and coaxTS, the latter two from three different manufacturers. Additionally, ∆P across the isolated 90°-connectors were determined. To test the clinical implications of our findings, the tubing related WOB and perception of discomfort of breathing through the different types of tubing systems were investigated in 14 volunteers. At a representative flow rate of 1.0 L/s coaxTS showed the highest ∆P (5.0±0.1 cmH2O), followed by cdTS (1.4±0.1 cmH2O) and crTS (1.3±0.1 cmH2O; two-way ANOVA, p<0.001). ∆P across coaxTS was significantly higher in expiration compared to inspiration (p<0.001) and varied between manufacturers (p<0.05). At the same flow rate the 90°- connector caused up to 40% from ∆P in cdTS but only 8% in crTS, respectively. Additional WOB was up to fourfold higher in coaxTS compared to crTS (4.0±2.3 vs. 0.95±0.53 J/min; one-way ANOVA, p<0.0001) and discomfort was rated the highest across coaxTS (11 from 14 volunteers). As a result from our study, coaxial tubing systems should be carefully considered in patients with pathologically increased airway resistance.

Biomed Tech 2016; 61 (s92) © by Walter de Gruyter • Berlin • Boston. DOI 10.1515/bmt-2016-5008 S92

ID: J-OP-04

Comparative Assessment of Stroke Patients' Upper Limb Tasks to Evaluate a System Based on Inertial Measurement Units and Fuzzy Logic

Braulio Roberto Duarte Benitez, Department of Rehabilitation & Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, Aachen, Germany, [email protected] Catherine Disselhorst-Klug, Department of Rehabilitation & Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, Aachen, Germany, [email protected]

According to the World Health Organization, per year 15 million people suffer a stroke worldwide. Of these, 5 million are permanently disabled. Currently there are several methods to evaluate upper limb movements on stroke patients; they are mostly based on observation by physicians and physiotherapists, whose judgement is influenced by experience and subjective impressions. This study was done on 16 stroke patients, using a system which is based on four Inertial Measurement Units (IMUs) which are composed of accelerometers, gyroscopes, and magnetometers. Each sensor was placed on each segment of the patient´s arm, i.e. scapula, arm, forearm, and hand. Every patient was told to perform simple movements with the arm, such as “move the hand to the mouth” and “hand to the head” starting from a resting position while they were standing, or sitting when requiring a wheelchair. Repeated movements were performed continuously between 15 and 20 times, while the data from the IMUs were recorded. Afterwards, the data were processed to obtain the orientation of every segment of the arm, given as Euler angles in relation to a laboratory coordinate system. The Euler angles were run through a Fuzzy Logic algorithm. The resulting values from a specific repetition were compared with other repetitions of the same exercise, assigning a score to each repetition based on a final scaled value between 0 and 10. Physiotherapists were asked to evaluate the patients´ movements. Comparing their evaluation with the proposed methodology, physiotherapists were able to highlight certain characteristics from the movements on a specific period of the exercise. In contrast with physiotherapists, Fuzzy algorithm considers and processes what the patient performed during the entire exercise. The outcome from the Fuzzy algorithm offered an objective, stable and consistent movement evaluation which was independent of the performed task and the analyzed patient.

Biomed Tech 2016; 61 (s93) © by Walter de Gruyter • Berlin • Boston. DOI 10.1515/bmt-2016-5008 S93

ID: J-OP-05

In vitro assessment of the effects of high glucose levels on rheological blood parameters.

Steven Ndzengue, Institute for Multiphase Processes, Leibniz Universität Hannover, Germany, [email protected] Marc Müller, Institute for Multiphase Processes, Leibniz Universität Hannover, Germany, [email protected] Jörg Vienken, Usingen, Germany, [email protected] Birgit Glasmacher, Institute for Multiphase Processes, Leibniz Universität Hannover, Germany, [email protected]

Diabetic patients suffering from a nephropathy are candidates for a hemodialysis treatment which is related with a lower survival outcome compared to hemodialysis patients from other underlying diseases. Apart from providing energy by oxidation, glucose can also be stored in the organism. Beyond this energetic function, elevated blood glucose levels also lead to changes in blood composition. It can be assumed, that rheological changes of blood from hyperglycemic or even diabetic patients have a direct impact on the effectiveness of the hemodialysis treatment. The aim of the study is to investigate the effects of high blood glucose levels on rheological blood parameters by exposing blood from healthy pigs to an in vitro artificial diabetic environment. The corpuscular blood components as well as clinically relevant rheological variables were examined in porcine citrate blood samples with different glucose concentrations. Purpose-built one-molar glucose solutions were added into blood samples in order to reach the required final concentrations (5, 11.11 and 13.88 mmol/L). Hematocrit (Hct) as well as thrombocytes concentration (Thr) among others were assessed every 30 min in blood vials held under dynamic conditions for up to 3 hours at 37 °C using an automatic hematology system. Clotting time (Clt) was also measured using a coagulation system. Normoglycemic samples with native glucose concentration in range from 3.9 to 4.5 mmol/L served as control and just remained untreated. The samples treated with glucose showed a lower Clt compared to the controls. Clt decreased with increasing glucose concentrations. Hematocrit increased with time and increasing glucose concentrations while thrombocytes concentration decreased with time and decreasing glucose concentrations. Elevated blood glucose levels lead to faster clotting, lower thrombocytes concentration and higher hematocrit. Consequently, a disturbed blood flow is expected to negatively affect the effectiveness of dialysis.

ID: J-PP-01

Camera-based pulse transition time measurement for blood pressure estimation

Fabian Schrumpf, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Juliane Bauer, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Bianca Reichard, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Daniel Matthes, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Mirco Fuchs, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected]

Photoplethysmograhpy (PPG) is a technique that allows non-invasive monitoring of blood volume dynamics by means of optical sensors. It is usually sensed at a finger or the wrist and used for pulse rate, respiratory rate, and even blood pressure estimation. The latter is correlated to the pulse wave velocity which can be estimated by means of the pulse transit time (PTT), i.e. the time in which a pulse wave passes a certain distance. One approach to determine the PTT is measuring the time difference between the electrical stimulation of the heart and the systolic peak amplitude in the PPG signal. Another method is solely based on the PPG signal, i.e. on time differences between the maximum systolic and diastolic amplitude. In recent years, the PPG principle has been utilized by several research groups for camera-based pulse rate detection by means of remote PPG (rPPG). That is, blood volume dynamics are estimated on the basis of particular color information in consecutive pictures of, e.g., the face. However, rPPG signals are prone to errors due to, e.g., movement and ambient light. This usually leads to a poor signal quality. Therefore, none of the available methods to estimate the PTT is actually suited for camera-based measurements. In this work we present a new method which aims to provide PTT estimation for camera-based applications. It is based on the idea to detect rPPG signals in at least two distinct face regions. The PTT between these regions is going to be determined by means of cross-correlation. The method is systematically evaluated according to the location of the employed regions using experimental data. Our method is the basis for the camera-based detection of blood pressure which might open a wide range of medical and home care applications.

ID: J-PP-02

Skin detection based ROI selection for the analysis of rPPG signals in newborns

Daniel Matthes, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Christoph Mönch, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Fabian Schrumpf, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Mirco Fuchs, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected] Gerold Bausch, Laboratory for Biosignal Processing, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany, [email protected]

Remote photoplethysmography (rPPG) is a technique that allows the camera-based detection of blood volume dynamics in arteries located in the upper skin layers. It is based on the absorption of characteristic wavelength in visible light caused by, e.g., oxygenated hemoglobin. Since the amount of oxygenated blood is modulated by the heart beat rPPG allows, e.g., the estimation of the heart frequency only by means of a camera. We utilized this method for the non-invasive measurement of several vital parameters in newborns. A major issue for such an application is the automated robust detection of regions (ROIs) in which strong signals can be expected, usually the forehead or the cheek. Common approaches employ face detection (e.g., according to Viola/Jones) and a subsequent offset-based placement of the ROIs. However, this usually require (1) recording from a frontal direction, and (2) opened eyes of the recorded person in order to provide stable results. We propose an alternative approach that is based on skin detection by means of the hue component in HSV color space and an adaptive optimization of skin detection parameters. The hue is particularly suited since it is widely independent from the lighting conditions. We further applied edge detection algorithms to identify other skin colored objects close to the head, e.g., hands and arms of newborns. Next, the detected skin area is used to estimate the facial region by means of fitting an ellipsoid. This is used as a reference to finally place the desired ROIs. We applied our method to the rPPG-based detection of the pulse frequency in newborns. We conducted datasets of 30 healthy newborns at several maternal wards. A Finger-clip based measurement served as reference. Our method provides a stable detection of the pulse, even in situations where other face detection based methods provide no results at all.