Advances in Respiratory Monitoring: A Comprehensive Review of Wearable and Remote Technologies

Abstract

This article explores the importance of wearable and remote technologies in healthcare. The focus highlights its potential in continuous monitoring, examines the specificity of the issue, and offers a view of proactive healthcare. Our research describes a wide range of device types and scientific methodologies, starting from traditional chest belts to their modern alternatives and cutting-edge bioamplifiers that distinguish breathing from chest impedance variations. We also investigated innovative technologies such as the monitoring of thorax micromovements based on the principles of seismocardiography, ballistocardiography, remote camera recordings, deployment of integrated optical fibers, or extraction of respiration from cardiovascular variables. Our review is extended to include acoustic methods and breath and blood gas analysis, providing a comprehensive overview of different approaches to respiratory monitoring. The topic of monitoring respiration with wearable and remote electronics is currently the center of attention of researchers, which is also reflected by the growing number of publications. In our manuscript, we offer an overview of the most interesting ones.

Keywords: acoustic methods; airflow; impedance; respiration monitoring; thorax movement; wearable devices.

Figure 1

Respiration wearables statistics [19]: (a) marketed devices; (b) research works.

Figure 2

Wearable and remote respiratory sensors: (a) Resmetrix—chest strap powered by a proprietary sensor for monitoring breathing patterns, heart rate, temperature, activity, and position. Reprinted from ref. [20]; (b) Spire Health Tag—force respiratory tracker attached to clothing enhanced by physical activity and heart rate sensors. Reprinted from ref. [21]; (c) Respiration belt with embedded fiber optic sensors. Reprinted from ref. [22]; (d) Forcecardiography sensor for simultaneous monitoring of respiration, infrasonic cardiac vibrations, and heart sounds. Reprinted from ref. [23]; (e) soft skin-interfaced mechano-acoustic sensors for real-time monitoring and feedback on respiratory and swallowing biomechanics. Reprinted from ref. [24]; (f) Somnofy—ultra-low-power radar system for contactless analysis of RR and sleep stages [25]; (g) synergetic use of thermal and visible imaging techniques for contactless and unobtrusive breathing measurement. Reprinted from ref. [26]; (h) respiration derived from ECG amplitude-optimization of sensor placement. Reprinted from ref. [27]; (i) ePPG—own designed multisensor that calculates respiration from heart rate variability; (j) digital stethoscope Mintti Smartho-D2. Reprinted from ref. [28]; (k) acoustic and biopotential multi-sensor patch. Reprinted from ref. [29]; (l) dual-signal NH₃ sensor for diagnosis of chronic kidney disease. Reprinted from ref. [30]; (m) continuous transcutaneous monitoring of CO₂. Reprinted from ref. [31]; (n) flexible humidity sensor for sleep apnea monitoring. Reprinted from ref. [32]; (o) soft wearable flexible bioelectronics with bioimpedance measurement using ADS1292R (Texas Instruments, Dallas, TX, USA). Reprinted from ref. [33].