Validation of a self-applied unattended monitor for sleep disordered breathing.

STUDY OBJECTIVES To evaluate the validity of the Apnea Risk Evaluation System (ARES) Unicorder, a self-applied, limited-channel portable monitoring device for the evaluation of sleep disordered breathing (SDB). DESIGN Prospective study with blinded analysis. SETTING Sleep disorder center, academic institution. PARTICIPANTS Eighty patients with suspected obstructive sleep apnea hypopnea syndrome (OSAHS) and 22 volunteers. INTERVENTIONS N/A. MEASUREMENTS AND RESULTS Subjects used the ARES Unicorder at home for 2 nights using only written instructions. Within 2 weeks, they returned to the laboratory for full nocturnal polysomnography (NPSG) with simultaneous monitoring with the Unicorder. NPSGs were scored manually to obtain an apnea-hypopnea index based on Medicare guidelines (AHI4%) and a respiratory disturbance index (RDI). ARES studies were autoscored and reviewed to obtain indices based on equivalent definitions i.e., AHI4%(ARES) and apnea hypopnea (events with 1% desaturation) index (AHI1%(ARES)). Indices from the NPSG were compared to the in-lab ARES and in-home ARES indices using mean differences and the intraclass correlations (ICC). For the in-lab comparison, there was high concordance between AHI4%(NPSG) and AHI4%(ARES) (ICC = 0. 96, mean difference = 0.5/hour) and RDI(NPSG ) and AHI1%(ARES) (ICC =0.93, mean difference = 3.2/hour). For NPSG versus In-Home ARES comparison, there was good concordance between AHI4%(NPSG) and AHI4%(ARES) (ICC = 0.8, mean difference = 4.1/ hour) and RDI(NPSG) and AHI1%(ARES) (ICC = 0.8 mean difference = 8.6/hour). The diagnostic sensitivity of in-lab ARES for diagnosing SDB using an RDI cut-off of 15 per hour was 95% and specificity was 94%, with a positive likelihood ratio (LR+) =17.04, and negative likelihood ratio (LR-) = 0.06. For in-home ARES data the sensitivity was 85% and specificity 91% (LR+ = 9.34, LR- = 0.17). There was good agreement between the manually scored NPSG SDB indices and the autoscoring ARES algorithm. CONCLUSIONS ARES Unicorder provides acceptably accurate estimates of SDB indices compared to conventional laboratory NPSG for both the simultaneous and in-home ARES data. The high sensitivity, specificity, and positive and negative likelihood ratios obtained in the group we studied supports the utility of an ambulatory limited-monitoring approach not only for diagnosing sleep disordered breathing but also to rule out SDB in suitably selected groups.