Single-channel ECG suitable for ECG-derived respiration

Abstract

Electrocardiogram (ECG)-derived respiration (EDR) is a tool used for estimating respiration using ECG. EDR signals are often used to avoid the use of devices such as air flow sensors, pressure transducers. Several EDR algorithms have been proposed; however, an effective ECG channel for estimating respiration has not been studied. The aim of this study was to determine an effective ECG channel for accurately estimating respiration. Twelve novel ECG channels were placed around the lower chest, and six channels: NASA, CC5, CM1, CM2, CM4, and CM5 were used for comparison. To identify the effective ECG channels, we recorded the ECG and actual respirations in 47 subjects. The actual respiratory signals were measured using an air flow sensor and a pressure transducer. To estimate the respiration waveform, 11 EDR algorithms, including the principal component analysis, were employed. The evaluation indices used to determine the effective ECG channels were the root-mean-square percentage error (RMSPE), the correlation coefficient between the actual respiratory rates and those obtained from the estimated respiratory waveforms, and limit of agreement (LOA). A conclusive evaluation was performed based on two RMSPEs of the respiratory signals measured using the air flow sensor and pressure transducer, based on the two correlation coefficients obtained from them, and based on the LOA. The estimations were most accurate when the positive and negative electrodes were attached in a way that they could measure both the bucket-handle and pump-handle movements of the ribs and when one of the two electrodes was attached near the heart. (The channel called ALPHA in a body text yielded most accurate results: RMSPEs < 0.5, correlation coefficients > 0.8, and almost all ∣LOAs∣ 8.0.) The respiration estimated with one of the proposed ECG channels was more accurate than those with conventional ECG channels.