Estimating cardiac output based on gas exchange during veno-arterial extracorporeal membrane oxygenation in a simulation study using paediatric oxygenators.

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) therapy is a rescue strategy for severe cardiopulmonary failure. The estimation of cardiac output during VA-ECMO is challenging. A lung circuit ([Formula: see text]Lung) and an ECMO circuit ([Formula: see text]ECMO) with oxygenators for CO2 removal ([Formula: see text]CO2) and O2 uptake ([Formula: see text]O2) simulated the setting of VA-ECMO with varying ventilation/perfusion ([Formula: see text]/[Formula: see text]) ratios and shunt. A metabolic chamber with a CO2/N2 blend simulated [Formula: see text]CO2 and [Formula: see text]O2. [Formula: see text] Lung was estimated with a modified Fick principle: [Formula: see text]Lung = [Formula: see text]ECMO × ([Formula: see text] CO2 or [Formula: see text]O2Lung)/([Formula: see text]CO2 or [Formula: see text]O2ECMO). A normalization procedure corrected [Formula: see text]CO2 values for a [Formula: see text]/[Formula: see text] of 1. Method agreement was evaluated by Bland-Altman analysis. Calculated [Formula: see text]Lung using gaseous [Formula: see text]CO2 and [Formula: see text]O2 correlated well with measured [Formula: see text]Lung with a bias of 103 ml/min [- 268 to 185] ml/min; Limits of Agreement: - 306 ml/min [- 241 to - 877 ml/min] to 512 ml/min [447 to 610 ml/min], r2 0.85 [0.79-0.88]). Blood measurements of [Formula: see text]CO2 showed an increased bias (- 260 ml/min [- 1503 to 982] ml/min), clinically not applicable. Shunt and [Formula: see text]/[Formula: see text] mismatch decreased the agreement of methods significantly. This in-vitro simulation shows that [Formula: see text]CO2 and [Formula: see text]O2 in steady-state conditions allow for clinically applicable calculations of [Formula: see text]Lung during VA-ECMO therapy.

Estimation of Arterial Pulse Wave Velocity from Doppler Radar Measurements: a Feasibility Study.

Pulse wave velocity has emerged as important diagnostic parameter due to its association with various cardiovascular disorders, such as hypertension, vascular aging, and atherosclerosis. Long-term monitoring of pulse wave velocity can be beneficial in carrying out accurate diagnosis of the underlying conditions or even for an early prediction of cardiovascular diseases. Doppler radar has emerged as a promising technology for contact-less monitoring and assessment of physiological parameters. In this study, we aimed at: i) as a first step, assessing the feasibility of measuring arterial pulse waves at the femoral region using the Doppler radar technology, and consequently, ii) estimating the pulse transit time between the heart-femoral regions as well as between the carotid-femoral regions using simultaneous Doppler radar measurements. The results of our feasibility study demonstrate that the arterial pulse waves in the femoral region, arising due to cardiac activity, can be estimated using the Doppler radar technology in a contact-less fashion. Furthermore, simultaneous pulse wave measurements at distinct surface locations using this technique can enable contact-less estimation of the pulse transit time and consequently pulse wave velocity.

Augmented marker tracking for peri-acetabular osteotomy surgery.

OBJECTIVE: To develop a hybrid augmented marker-based navigation system for acetabular reorientation during peri-acetabular osteotomy (PAO). METHODS: The system consists of a tracking unit attached to the patient's pelvis, augmented marker attached to the acetabular fragment and a host computer to do all the computations and visualization. The augmented marker is comprised of an external planar Aruco marker facing toward the tracking unit and an internal inertial measurement unit (IMU) to measure its orientation. The orientation output from the IMU is sent to the host computer. The tracking unit streams a live video of the augmented marker to the host computer, where the planar marker is detected and its pose is estimated. A Kalman filter-based sensor fusion combines the output from marker tracking and the IMU. We validated the proposed system using a plastic bone study and a cadaver study. Every time, we compared the inclination and anteversion values measured by the proposed system to those from a previously developed optical tracking-based navigation system. RESULTS: Mean absolute differences for inclination and anteversion were 1.34 ([Formula: see text]) and 1.21 ([Formula: see text])[Formula: see text], respectively, for the cadaver study. Mean absolute differences were 1.63 ([Formula: see text]) and 1.55 ([Formula: see text])[Formula: see text] for inclination and anteversion for the plastic bone study. In both validation studies, very strong correlations were observed. CONCLUSION: We successfully demonstrated the feasibility of our system to measure the acetabular orientation during PAO.

K-band Doppler radar for contact-less overnight sleep marker assessment: a pilot validation study.

An estimated 45 million persons in Europe are annually subjected to sleep-wake disorders. State-of-the-art polysomnography provides sophisticated insights into sleep (patho)physiology. A drawback of the method, however, is the obtrusive setting dependent on a clinical-based sleep laboratory with high operational costs. A contact-less prototype was developed to monitor limb movements and vital signs during sleep. A dual channel K-band Doppler radar transceiver captured limb movements and periodic chest wall motion due to respiration and heart activity. A wavelet transform based multi-resolution analysis (MRA) approach isolated limb movements, respiration, and heart rate from the demodulated signal. A test bench setup characterized the prototype simulating near physiological chest wall motions caused by periodic respiration and heartbeats in humans. Single- and multi-tone test bench simulations showed extremely low relative percentage errors of the prototype for respiratory and heart rate within -2 and 1%. The performance of the prototype was validated in overnight comparative studies, involving two healthy volunteers, with polysomnography as the reference. The prototype has successfully classified limb movements, with a sensitivity and specificity of 88.9 and 76.8% respectively, and has achieved accurate respiratory and heart rate measurement performance with overall absolute errors of 1 breath per minute for respiration and 3 beats per minute for heart rate. This pilot study shows that K-band Doppler radar and wavelet transform MRA seem to be valid for overnight sleep marker assessment. The contact-less approach might offer a promising solution for home-based sleep monitoring and assessment.

Augmented marker tracking for peri-acetabular osteotomy surgery.

We developed and validated a small, easy to use and cost-effective augmented marker-based hybrid navigation system for peri-acetabular osteotomy (PAO) surgery. The hybrid system consists of a tracking unit directly placed on the patient's pelvis, an augmented marker with an integrated inertial measurement unit ('MU) attached to the patient's acetabular fragment and the host computer. The tracking unit sends a live video stream of the marker to the host computer where the marker's pose is estimated. The augmented marker with the 'MU sends its pose estimate to the host computer where we apply sensor fusion to compute the final marker pose estimate. The host computer then tracks the orientation of the acetabular fragment during peri-acetabular osteotomy surgery. Anatomy registration is done using a previously developed registration device. A Kalman filter-based sensor fusion was added to complete the system. A plastic bone study was performed for validation between an optical tracking-based navigation system and our proposed system. Mean absolute difference for inclination and anteversion was 1.63 degrees and 1.55 degrees, respectively. The results show that our system is able to accurately measure the orientation of the acetabular fragment.

An in vitro lung model to assess true shunt fraction by multiple inert gas elimination.

The Multiple Inert Gas Elimination Technique, based on Micropore Membrane Inlet Mass Spectrometry, (MMIMS-MIGET) has been designed as a rapid and direct method to assess the full range of ventilation-to-perfusion (V/Q) ratios. MMIMS-MIGET distributions have not been assessed in an experimental setup with predefined V/Q-distributions. We aimed (I) to construct a novel in vitro lung model (IVLM) for the simulation of predefined V/Q distributions with five gas exchange compartments and (II) to correlate shunt fractions derived from MMIMS-MIGET with preset reference shunt values of the IVLM. Five hollow-fiber membrane oxygenators switched in parallel within a closed extracorporeal oxygenation circuit were ventilated with sweep gas (V) and perfused with human red cell suspension or saline (Q). Inert gas solution was infused into the perfusion circuit of the gas exchange assembly. Sweep gas flow (V) was kept constant and reference shunt fractions (IVLM-S) were established by bypassing one or more oxygenators with perfusate flow (Q). The derived shunt fractions (MM-S) were determined using MIGET by MMIMS from the retention data. Shunt derived by MMIMS-MIGET correlated well with preset reference shunt fractions. The in vitro lung model is a convenient system for the setup of predefined true shunt fractions in validation of MMIMS-MIGET.