title: Elimination of Drifts in Long-Duration Monitoring for Apnea-Hypopnea of Human Respiration.
abstract: This paper reports a methodology to eliminate an uncertain baseline drift in respiratory monitoring using a thermal airflow sensor exposed in a high humidity environment. Human respiratory airflow usually contains a large amount of moisture (relative humidity, RH > 85%). Water vapors in breathing air condense gradually on the surface of the sensor so as to form a thin water film that leads to a significant sensor drift in long-duration respiratory monitoring. The water film is formed by a combination of condensation and evaporation, and therefore the behavior of the humidity drift is complicated. Fortunately, the exhale and inhale responses of the sensor exhibit distinguishing features that are different from the humidity drift. Using a wavelet analysis method, we removed the baseline drift of the sensor and successfully recovered the respiratory waveform. Finally, we extracted apnea-hypopnea events from the respiratory signals monitored in whole-night sleeps of patients and compared them with golden standard polysomnography (PSG) results.
authors: State Key Laboratory of Precision Measurement Technology and Instrument, Department of Precision Instrument, Tsinghua University, Beijing 100084, China. jiang-p13@mails.tsinghua.edu.cn.
authors: Peng
authors: P
authors: Jiang
authors: State Key Laboratory of Precision Measurement Technology and Instrument, Department of Precision Instrument, Tsinghua University, Beijing 100084, China. zr_gloria@mail.tsinghua.edu.cn.
authors: Rong
authors: R
authors: Zhu
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001049:Apnea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006813:Humidity; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods*; D017286:Polysomnography; D012123:Pulmonary Ventilation / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D014867:Water / Q000032:analysis; D058067:Wavelet Analysis
chemical_list: D014867:Water
keywords: hot-film airflow sensor; humidity drift; sleep apnea; wavelet analysis