Impedance plethysmography system with inertial measurement units for motion artefact reduction: Application to continuous breath activity monitoring

Abstract

This paper presents an impedance plethysmography system suitable to perform a continuous monitoring of human breath activity. The problem of motion artifact is mitigated through the use of a correction technique exploiting an additional inertial sensor able to detect movements of the arms of the subject under test. The correction algorithm is based on a simple correlation technique and only requires a very brief training at the beginning of the acquisition session, with the monitored subject performing random movements in apnea condition. Application of the proposed system to a healthy adult volunteer demonstrates the potentiality of the correction algorithm, which, thanks to its extreme simplicity and low computational cost, is a suitable candidate for implementation in a low-cost and portable monitoring system

Advanced Computing Methods for Impedance Plethysmography Data Processing

“…Graph from the Figure 2 clearly shows the quasi-periodic fluctuations caused by the patient’s breathing, where there are two components in the rheographic signal [ 13 ]: a useful rheographic signal to reflect fluctuations in blood supply to the organ or limb under test caused by heartbeat; slow baseline drift due to patient breathing (jamming signal). …”

“…In order to extract the impedance of the variable against the background of the dominant base impedance , the existing rheographs use low and high pass filters [ 4 , 9 , 13 ]. The implementation of analog high-pass filters with a very low cut-off frequency of 0.05–0.3 [Hz] to separate the proportional voltage is based on high-capacity capacitors, and the instability of the filter parameters results in phase distortions of the registered rheograms.…”

“…The accuracy of rheographic examinations depends not only on the technical parameters of the rheographs, but also on the methods of developing the rheograms. These methods can be used to eliminate distortions, mainly caused by the breath, as well as to intelligently analyze rheograms to obtain many medical indicators [ 13 , 24 , 25 , 26 , 27 ]. It is also important to test the effectiveness of various compression methods, which will make it possible to reduce the volume of archives of the recorded rheographic runs, which are the primary document of the test result.…”