An investigation of the validity of the Lifeshirt in comparison to standard polysomnography in the detection of obstructive sleep apnea

Background: Due to the cost and waiting times for traditional sleep studies, there is great interest in finding alternatives for the diagnosis of sleep apnea. Several alternatives exist, including ambulatory devices. Our laboratory utilized one such device, a form-fitting vest called the Lifeshirt, and compared its accuracy to that of polysomnography (PSG). Methods: PSG was performed with simultaneous utilization of the Lifeshirt on 50 individuals who met screening criteria for obstructive sleep apnea. Participants came to the sleep laboratory approximately 2 h before their normal bedtime. A sleep technician prepared each participant for PSG and Lifeshirt monitoring. "Lights Out" occurred when the participant was ready for bed, and time in bed was standardized to approximately 7 h. PSGs were scored by experienced personnel in our laboratory, while Lifeshirt data were sent electronically to the Lifeshirt manufacturer for analysis. The major variable that was compared between PSG and Lifeshirt was the apnea hypopnea index (AHI), or the number of apneas and hypopneas per hour. Due to incomplete data on two participants, analyses were completed on 48 individuals. Results: Sensitivity of the Lifeshirt ranged from .85 (AHI of >= 5) to 1.00 (AHI of >= 25). Specificity ranged from .67 to 1.00. Using the Bland-Altman technique of determining agreement, the mean difference between the AHI of the Lifeshirt and PSG was 1.02 (+/- 16.36). When these values are plotted, every case falls within the limits of agreement, with one exception. Conclusions: The Lifeshirt compared favorably with PSG and could be used with considerable confidence for the screening of patients with suspected obstructive sleep apnea. (C) 2007 Elsevier B.V. All rights reserved.