Ákos Jobbágy

Introduction: Non-invasive measurement of blood pressure in patients with a left ventricular assist device (LVAD) is challenging due to the mechanical properties of these circulatory support devices. Keeping blood pressure in a target range is crucial to reduce the risk of LVAD complications. As current assessment methods require trained personnel resulting in infrequent monitoring, devices for home-based measurements are sorely needed. Objectives: In this paper, we report a measurement method and a custom-made monitoring device based on photoplethysmography (PPG) enabling automated measurement of the mean arterial pressure (MAP) of patients with LVAD. Methods: The method and the device were tested on 21 adult patients with LVAD, and the estimated MAP values were compared to MAP values measured simultaneously by a human expert applying the commonly used Doppler-based method. Results: Results of the proposed method showed highly significant correlation with Doppler-based MAP values ( R = 0.85 for inflation, p < 0.001; R = 0.96 for deflation, p<0.001). The mean difference of the proposed method to the Doppler-based MAP values was 1.48 ± 5.43 mmHg for inflation and −0.19 ± 2.71 mmHg for deflation. Conclusion: The results demonstrate that the proposed method is a promising direction to achieve accurate, automated, non-invasive BP measurement, applicable in home health monitoring for patients with LVAD.

Background: Pulse wave transit time (PWTT) is widely used to characterize the dynamic properties of the arteries. PWTT is most often calculated as the time interval from the R peak in the electrocardiogram (start of the pulse wave) to the rise in the finger photoplethysmogram (arrival of the pulse wave). This is the PWTTHF. The aim of this study was to analyse the effect of cuff occlusion on PWTT, and using this information to improve the reliability of cuff-based indirect blood pressure (BP) measurement.Methods: PWTT was measured with a home health monitoring device that inflates and deflates the cuff slowly (6 mmHg/s). The change in the arterial wall rigidity caused by cuff occlusion is different in the parts of the arterial section proximal and distal to the cuff. Accordingly, PWTT was divided into two parts: PWTT from the heart to the cuff (PWTTHC) and PWTT from the cuff to the fingertip (PWTTCF). Seven patients with various cardiovascular diseases (55–66 years old), seven healthy senior subjects (55–65 years old) and seven healthy young subjects (22–26 years old) were included in the research.Results: Changes in PWTT characterise appropriately the effect of cuff occlusion on BP measurement. Cuff occlusion affected PWTTHC and PWTTCF differently; it increased the former and decreased the latter. Increased PWTTHC reflects a less rigid arterial wall, resulting in an underestimation of BP. The changes in PWTT values are person-specific and not group-specific (patient, healthy senior, and healthy youth).Conclusion: Occlusion with the cuff is an excitation to the cardiovascular system, causing a temporary change in the dynamic properties of the arteries from the heart to the cuff. The change influences the result of indirect BP measurement. Arterial rigidity in the part proximal to the cuff can be characterized by PWTTHC, which provides different information about the arteries than the widely used PWTTHF.

This paper introduces a smart nine-hole peg tester (s-9HPT), which comprises a standard nine-hole peg test pegboard, but with light-emitting diodes (LEDs) next to each hole. The s-9HPT still supports the traditional nine-hole peg test operating mode, in which the order of the peg placement and removal can be freely chosen. Considering this, the s-9HPT was used in lab research to analyze the traditional procedure and possible new procedures. As this analysis required subjects with similar levels of dexterity, measurement data from 16 healthy subjects (seven females, nine males, 25–80 years old) were used. We consequently found that illuminating the LEDs in various patterns facilitated guided tests of diverse complexity levels. Next, to demonstrate the clinical application of the s-9HPT, the improvement in the hand dexterity of 12 hospitalized stroke patients (45–80 years old, six females and six males) was monitored during their rehabilitation. Here, we used traditional and guided tests validated by healthy subjects. Consequently, improvements were found to be patient specific. At the beginning of rehabilitation, traditional tests suitably indicate improvements, while guided tests are beneficial following improvements in motor functions. Further, the guided tests motivated certain patients, meaning the rehabilitation was more effective for these individuals.

The increased stress level of an individual often influences the medical test results. Heart rate variability (HRV) can be used to characterize stress level. Parameters in the time domain are preferred, as they make the assessment possible from relatively short (3 - 5 minute-long) recordings. Electrocardiographic signal (ECG) in Einthoven I lead and photoplethysmographic signal (PPG) at the fingertip were recorded in parallel. This paper analyzes the differences between the lengths of successive heart cycles (NN); the ratio of these differences exceeding 50 ms (pNN50) is considered to be a good measure of stress. The parameter triplet pNNtri has been defined dividing the differences of successive NN intervals into three categories: pNN0_20 (0 – 20 ms), pNN20_50 (20 – 50 ms) and pNN50 (greater than 50 ms). pNNtri characterizes the actual stress level significantly better (especially for senior persons) than pNN50 alone. NN intervals determined from PPG differ from those determined from ECG recorded in parallel.

Sitting in a Huple, a patented hemisphere-like tool, permanently stimulates the vestibular system, thus improving the balancing ability of children with movement disorders. The Gézengúz Foundation for Children with Birth Injuries has been successfully applying this tool in therapy. By attaching x-Inertial Measurement Unit, a wireless three-dimensional orientation sensor, to the Huple, it can serve as an input peripheral for simple PC games. Children are thus motivated; they willingly perform balance training as well as participate in the game-like test. This improves the accuracy and reproducibility of the assessment. Knowing the actual state of the participants is an important element of feedback for the therapy. This paper describes in detail the development of the therapeutic and assessment method on the basis of the Huple: the definition of the movement pattern, the parameters characterizing the movement, and the algorithms used to rank children. Measurement series of 10 children with movement disorders validate the effectiveness of the game-like assessment.