Respiration Monitoring via Forcecardiography Sensors

Abstract

In the last few decades, a number of wearable systems for respiration monitoring that help to significantly reduce patients’ discomfort and improve the reliability of measurements have been presented. A recent research trend in biosignal acquisition is focusing on the development of monolithic sensors for monitoring multiple vital signs, which could improve the simultaneous recording of different physiological data. This study presents a performance analysis of respiration monitoring performed via forcecardiography (FCG) sensors, as compared to ECG-derived respiration (EDR) and electroresistive respiration band (ERB), which was assumed as the reference. FCG is a novel technique that records the cardiac-induced vibrations of the chest wall via specific force sensors, which provide seismocardiogram-like information, along with a novel component that seems to be related to the ventricular volume variations. Simultaneous acquisitions were obtained from seven healthy subjects at rest, during both quiet breathing and forced respiration at higher and lower rates. The raw FCG sensor signals featured a large, low-frequency, respiratory component (R-FCG), in addition to the common FCG signal. Statistical analyses of R-FCG, EDR and ERB signals showed that FCG sensors ensure a more sensitive and precise detection of respiratory acts than EDR (sensitivity: 100% vs. 95.8%, positive predictive value: 98.9% vs. 92.5%), as well as a superior accuracy and precision in interbreath interval measurement (linear regression slopes and intercepts: 0.99, 0.026 s (R2 = 0.98) vs. 0.98, 0.11 s (R2 = 0.88), Bland–Altman limits of agreement: ±0.61 s vs. ±1.5 s). This study represents a first proof of concept for the simultaneous recording of respiration signals and forcecardiograms with a single, local, small, unobtrusive, cheap sensor. This would extend the scope of FCG to monitoring multiple vital signs, as well as to the analysis of cardiorespiratory interactions, also paving the way for the continuous, long-term monitoring of patients with heart and pulmonary diseases.

A Novel Broadband Forcecardiography Sensor for Simultaneous Monitoring of Respiration, Infrasonic Cardiac Vibrations and Heart Sounds

“…This study presented a novel piezoelectric force sensor for simultaneous monitoring of respiration (FRG), infrasonic cardiac vibrations (LF-FCG, HF-FCG) and heart sounds (HS-FCG). The novel sensor was compared to the FSR-based sensor proposed in Andreozzi et al (2020Andreozzi et al ( , 2021 by carrying out measurements on six healthy volunteers, while breathing at rest. The FCG signals provided by the two compared sensors turned out to be very similar, proving that the novel PZT sensor is suitable for FCG.…”

“…In particular, a novel FCG sensor based on a small piezoelectric lead-zirconatetitanate (PZT) disk is demonstrated to be a suitable device for multimodal cardiorespiratory sensing, offering the opportunity to monitor respiration, heart sounds, seismocardiogram and the potentially ventricular-volume-related signal (i.e., the LF-FCG), simultaneously from one single signal: the forcecardiogram. The piezoelectric sensor was first compared, in terms of signal morphology, with the FSR-based sensor that had been originally employed to develop the FCG technique (Andreozzi et al, 2020(Andreozzi et al, , 2021. Then, the cardiorespiratory monitoring performances of the piezoelectric sensor were assessed via comparison with a respiratory electro-resistive band (ERB) (Jayarathna et al, 2020) and an ECG monitor, considered as benchmarks for respiratory and heart rate measurement, respectively.…”

Data_Sheet_1.CSV

“…The FSR was equipped with a dome-shaped mechanical coupler, so as to ensure a good transduction of the force to its active area. Considering the linear relationship between the applied force and the FSR electrical conductance, a conditioning circuit based on a transimpedance amplifier was used, which ensured high linearity while minimizing the sensor drift by keeping the voltage across the FSR at a constant value (Paredes-Madrid et al, 2017a,b;Esposito et al, 2018;Andreozzi et al, 2020Andreozzi et al, , 2021.…”

“…In addition to MEMS sensors, also piezoelectric sensors have been investigated for SCG recording (Bifulco et al, 2014;Ha et al, 2019;Nayeem et al, 2020). Very recently, the novel Forcecardiography (FCG) technique has been proposed (Andreozzi et al, 2020(Andreozzi et al, , 2021. FCG is based on the use of customdesigned force sensors (FCG sensors) that allow measuring the heart-induced vibrations of chest wall (Andreozzi et al, 2020) and the respiratory activity simultaneously (Andreozzi et al, 2021), thus standing as a novel promising technique for cardiorespiratory monitoring.…”

“…Very recently, the novel Forcecardiography (FCG) technique has been proposed (Andreozzi et al, 2020(Andreozzi et al, , 2021. FCG is based on the use of customdesigned force sensors (FCG sensors) that allow measuring the heart-induced vibrations of chest wall (Andreozzi et al, 2020) and the respiratory activity simultaneously (Andreozzi et al, 2021), thus standing as a novel promising technique for cardiorespiratory monitoring. FCG sensors are based on force sensitive resistors (FSR) that have already proved viable for muscle contraction monitoring (Esposito et al, 2018) and hand gestures recognition (Esposito et al, 2020).…”