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(Chest. 2005;128:1331-1338.)
© 2005 American College of Chest Physicians

Comparison of Respiratory Event Detection by a Polyvinylidene Fluoride Film Airflow Sensor and a Pneumotachograph in Sleep Apnea Patients*

Richard B. Berry, MD; Gary L. Koch; Steven Trautz and Mary H. Wagner, MD

* From the Departments of Medicine (Dr. Berry, Mr. Koch, and Mr. Trautz) and Pediatrics (Dr. Wagner), University of Florida, Gainesville, FL.

Correspondence to: Richard B. Berry, MD, Box 100225 HSC, University of Florida, Gainesville, FL 32610; e-mail: sleep_doc{at}msn.com

Study objectives: Compare the ability of a polyvinylidene fluoride (PVDF) thermal sensor and a pneumotachograph to detect respiratory events in patients with obstructive sleep apnea.

Design: Single night of monitoring, single blinded scorer.

Setting: Veterans Affairs medical center.

Patients: Ten male subjects with obstructive sleep apnea.

Interventions: Nasal-oral airflow was simultaneously detected by a PVDF thermal sensor attached to the upper lip and a pneumotachograph in a mask over the nose and mouth.

Measurements: Events were scored from display views showing only the airflow tracings of the sensor in question and the events scored from that sensor. The apnea-hypopnea index was computed using two definitions for hypopnea. Hypopnea-1 was defined as a 50% reduction in flow for ≥ 10 s in duration. Hypopnea-2 was defined as any reduction in airflow for ≥ 10 s associated with a 3% drop in the arterial oxygen saturation or followed by an arousal. The level of agreement ({kappa}) for the sensors was determined by comparing whether or not they identified candidate events determined by a second blinded scorer.

Results: For the apnea-hypopnea-1 index (mean ± SD), the event rate for the pneumotachograph (26.0 ± 27.9 events/h) was slightly greater than that for the PVDF sensor (20.1 ± 27.1 events/h; p < 0.05). For the apnea-hypopnea-2 index, the event rate for the pneumotachograph (29.4 ± 26.8 events/h) and for that of the PVDF sensor (26.4 ± 25.9 events/h) were similar (difference not significant). The mean ± 2 SD difference was 3.0 ± 8.5 events/h. The level of agreement between the sensors was in the "good range," whereby {kappa} = 0.69. For 20 randomly selected breaths per patient, the maximum deflections of the PVDF sensor varied linearly with pneumotachograph airflow deflections.

Conclusion: The PVDF sensor compared favorably with a "gold standard" method of detecting respiratory events during sleep in patients with obstructive sleep apnea.

Key Words: airflow • pneumotachograph • sleep apnea






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