ASSESSMENT OF ACCURACY AND ANALYSIS TIME OF A NOVEL DEVICE TO MONITORSLEEP AND BREATHING IN THE HOME

Obstructive sleep apnea is increasingly recognized as a common and deb ilitating disorder. As a result, a variety of diagnostic technologies have evolved to potentially decrease cost and improve access and ease of assessment, In this study we compared the Healthdyne NightWatch (NW ) System (a home sleep diagnostic methodology) to standard polysomnogr aphy (PSC) in two sleep centers. Two separate studies were completed. NW was compared to a simultaneously obtained PSG in 30 patients (IN-LA B study). Seventy additional patients were studied in both the home wi th NW and in the laboratory with PSG (HOME-LAB study). The NW system r ecords eye movement, leg movement, SaO(2), nasal-oral airflow, chest a nd abdominal wall motion, body position and heart rate on a solid stat e recorder, which permits sleep staging based on body and eye movement and standard respiratory assessment. For the PSG, standard paper reco rding techniques were used. The IN-LAB study revealed a correlation be tween NW and PSG for total sleep time of r = 0.72, with NW tending to score some awake time as nonrapid eye movement sleep. The correlation for apnea-hypopnea index (AHI) was r = 0.94 between systems, with a se nsitivity of 100% and specificity of 63.6% at an AHI threshold of 10. The HOME-LAB study demonstrated understandably poor correlations betwe en NW and PSG for most measures of sleep, which is likely a product of night-to-night variability in sleep, home versus laboratory effects a nd the differences in sleep staging methodology. However, the correlat ion for AHI was r = 0.92, with a sensitivity of 90.7% and a specificit y of 70.4% at an AHI threshold of 10. Using a new methodology to asses s agreement between diagnostic systems, we observed 78.6% diagnostic a greement between NW and PSG in the HOME-LAB study, with NW underestima ting AHI 4.3% of the time and overestimating it in 17.1% of cases. Thi s may relate to night-to-night variability in AHI or greater NW comput er sensitivity to subtle hypopneas. We conclude that NW provides an ac curate determination of AHI in both the home and laboratory, using lim ited instrumentation. The analysis time for NW is also reduced compare d to PSG, and patients generally prefer the NW evaluation.