Objective: To assess the sensitivity and specificity of a portable sleep apnea monitoring device (PolyG; CNS Inc; Chantassen, Minn) using standard polysomnography (PSG) as a gold standard.
Setting: The University of Alberta Hospitals Sleep Disorders Laboratory.
Participants: One hundred and four consecutive patients referred for assessment of sleep complaints.
Measurements: Patients underwent simultaneous PSG and PolyG overnight recordings. The PSG included recordings of EEG, Chin electromyogram, electroculogram, ECG, oronasal airflow, thorax and abdomen respiratory movements, bilateral tibialis anterior electromyogram, and ear oximetry. The PolyG monitoring included oronasal airflow (thermistors), chest and abdomen pneumobelts, oximetry, ECG, and body position sensor. The raw data were screened and analyzed separately by two technicians without knowledge of results of the other system.
Results: The coefficient of correlation for apnea index (AI) was 0.94. The r value for apnea-hypopnea index (AHI) was 0.97. Using the criteria of AI more than 5 as diagnostic for sleep apnea syndrome, 23 out of the 104 patients had the disease based on PSG results. Twenty-six patients had AI more than 5 based on PolyG results. The sensitivity was 82.6% and the specificity was 91.4%. The positive predictive value was 73.1% and the negative predictive value was 94.9%. The overall accuracy was 89.4%. Using the criteria of AHI more than 15 as diagnostic for sleep apnea syndrome, 28 of the 104 patients had the disease based on the PSG results. Twenty-four patients had AHI more than 15 based on PolyG results. The sensitivity was 85.7% and the specificity was 94.7%. The positive predictive value was 85.7% and the negative predictive value was 94.7%. The overall accuracy was 92.3%.
Conclusion: The PolyG monitoring device is useful in identifying patients without significant sleep apnea.