Aim: Continuous respiratory monitoring is crucial in managing respiratory conditions. Traditional methods, such as spirometry, require medical equipment and experts, causing discomfort to patients and increasing socioeconomic burden. Furthermore, most traditional methods are only suitable for discrete measurements. To address these challenges, noninvasive techniques like thoracic bioimpedance or ECG-derived respiration (EDR) have been investigated. Wearable devices can provide comfortable, continuous, and noninvasive measurement of physiological signals like ECG. Therefore, wearable EDR could be a potential unobtrusive approach for respiratory monitoring. This study aims to evaluate respiratory pattern estimation from a novel wearable patch device with a nonstandard single-lead ECG signal, compared to bioimpedance and standard airflow.
Methods: 10 healthy volunteers performed a protocol consisting of breathing freely and following three respiratory rates (RR) (6, 12, and 15 breaths/min), while acquiring physiological signals. ECG (nonstandard single-lead) and bioimpedance signals were recorded with a custom wearable device placed on the chest, simultaneously with the reference respiratory airflow, using a standard system. An R-wave amplitude method was applied to extract the EDR. We detected respiratory cycles and estimated common breathing pattern parameters using the EDR, bioimpedance, and airflow signals. The EDR and bioimpedance respiratory estimations were compared to the airflow in terms of correlation, accuracy, and errors.
Results: The correlation between the EDR signal and the airflow reference was 0.90±0.08, showing an excellent alignment. The EDR signal detected the respiratory cycles with an accuracy of 94.97%. In terms of mean absolute error, the RR was estimated with an error of 0.73breaths/min, corresponding to a mean average percentage error (MAPE) of 5.70%. Regarding bioimpedance performance, it showed good results (correlation: 0.70±0.41, accuracy:91.33%, MAPE:7.61%), but being lower than the EDR performance.
Conclusions: This study reinforces the use of wearable devices for respiratory monitoring, specifically the use of EDR from a new patch for ambulatory purposes.