Objective: This study was designed to assess the sensitivity and specificity of a portable sleep apnea recording device (ApneaLink) using standard polysomnography (PSG) as a reference and to evaluate the possibility of using the ApneaLink as a case selection technique for patients with suspected obstructive sleep apnea (OSA).
Materials and methods: Fifty patients (mean age 48.7 +/- 12.6 years, 32 males) were recruited during a 4-week period. A simultaneous recording of both the standard in-laboratory PSG and an ambulatory level 4 sleep monitor (ApneaLink) was performed during an overnight study for each patient. PSG sleep and respiratory events were scored manually according to standard criteria. ApneaLink data were analyzed either with the automated computerized algorithm provided by the manufacturer following the American Academy of Sleep Medicine standards (default setting DFAL) or The University of British Columbia Hospital sleep laboratory standards (alternative setting, ATAL). The ApneaLink respiratory disturbance indices (RDI), PSG apnea-hypopnea indices (AHI), and PSG oxygen desaturation index (ODI) were compared.
Results: The mean PSG-AHI was 30.0 +/- 25.8 events per hour. The means of DFAL-RDI and ATAL-RDI were 23.8 +/- 21.9 events per hour and 29.5 +/- 22.2 events per hour, respectively. Intraclass correlation coefficients were 0.958 between PSG-AHI and DFAL-RDI and 0.966 between PSG-AHI and ATAL-RDI. Receiver operator characteristic curves were constructed using a variety of PSG-AHI cutoff values (5, 10, 15, 20, and 30 events per hour). Optimal combinations of sensitivity and specificity for the various cutoffs were 97.7/66.7, 95.0/90.0, 87.5/88.9, 88.0/88.0, and 88.2/93.9, respectively for the default setting. The ApneaLink demonstrated the best agreement with laboratory PSG data at cutoffs of AHI >or= 10. There were no significant differences among PSG-AHI, DFAL-RDI, and ATAL-RDI when all subjects were considered as one group. ODI at 2%, 3%, and 4% desaturation levels showed significant differences (p < 0.05) compared with PSG-AHI, DFAL-RDI, and ATAL-RDI for the entire group.
Conclusion: The ApneaLink is an ambulatory sleep monitor that can detect OSA and/or hypopnea with acceptable reliability. The screening and diagnostic capability needs to be verified by further evaluation and manual scoring of the ApneaLink. It could be a better choice than traditional oximetry in terms of recording respiratory events, although severity may be under- or overestimated.