Abstract
Respiratory rate and changes in respiratory activity provide important markers of health and fitness. Assessing the breathing signal without direct respiratory sensors can be very helpful in large cohort studies and for screening purposes. In this paper, we demonstrate that long-term nocturnal acceleration measurements from the wrist yield significantly better respiration proxies than four standard approaches of ECG (electrocardiogram) derived respiration. We validate our approach by comparison with flow-derived respiration as standard reference signal, studying the full-night data of 223 subjects in a clinical sleep laboratory. Specifically, we find that phase synchronization indices between respiration proxies and the flow signal are large for five suggested acceleration-derived proxies with gamma = 0.55 pm 0.13 for males and 0.58 pm 0.14 for females (means ± standard deviations), while ECG-derived proxies yield only gamma = 0.36 pm 0.16 for males and 0.39 pm 0.14 for females. Similarly, respiratory rates can be determined more precisely by wrist-worn acceleration devices compared with a derivation from the ECG. As limitation we must mention that acceleration-derived respiration proxies are only available during episodes of non-physical activity (especially during sleep).
Highlights
Respiratory rate and changes in respiratory activity provide important markers of health and fitness
We have introduced and validated an approach for obtaining respiration proxies from nocturnal long-term wrist acceleration measurements from 223 clinical subjects including patients with various sleep-related disorders
We have shown that each of the the suggested five acceleration-derived proxies is significantly ( p < 0.001 ) more reliable than each of the four known standard ECG-derived respiration proxies, exploiting ECG baseline, amplitude, and frequency changes
Summary
Respiratory rate and changes in respiratory activity provide important markers of health and fitness. We demonstrate that long-term nocturnal acceleration measurements from the wrist yield significantly better respiration proxies than four standard approaches of ECG (electrocardiogram) derived respiration. In a very recent study of non-invasive risk assessment for cardiac patients, abnormally high respiratory rate (> 18.6 bpm ) and low expiration-triggered sinus arrhythmia turned out to be among the three most sensitive early risk indicators as components of the Polyscore index[5]; previous work demonstrated the importance of respiratory rate for cardiac p atients[6,7]. It is appropriate to include measurements of respiratory rate and the influence of respiration activity on the heart in large cohort studies that aim at identifying early indicators for health risks and to study effects of healthy a ging[8,9]. Description Wrist acceleration in longitudinal direction (in mg) Wrist acceleration in lateral direction (in mg) Wrist acceleration in lateral direction (in mg) rotational angle of the wrist (in rad) rotational angle of the wrist (in rad) Average of maximum and minimum of QRS complex (in μV) Difference of maximum and minimum of QRS complex (in μV) Duration of RR interval (in ms) Maximum of QRS complex (in μV)
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