Comparison of a cardiorespiratory device versus polysomnography for diagnosis of sleep apnoea

This study assessed the accuracy of a cardiorespiratory monitoring device versus polysomnography for the diagnosis of suspected sleep apnoea/hypoponea syndrome (SAS). A total of 86 patients (89% male, mean age 52 yrs) that had been referred to a sleep laboratory with a clinical diagnosis of SAS underwent cardiorespiratory polygraphy in an unattended mode using an ambulatory device (MERLIN). Analysis was carried out both automatically and manually. Conventional overnight full-channel polysomnography was performed simultaneously. Valid polygraphical recordings were obtained from 79 patients. The mean sD apnoea/hypopnoea index (AHI) was 34.4+/-29.2. The results obtained with manual scoring were superior to automatic scoring for all AHI thresholds. For an AHI of greater than or equal to5, which is diagnostic SAS, the optimum cut-off value for the manual respiratory event index was 6.7 and the cardiorespiratory monitoring device had 97.1%, sensitivity and 90.9% specificity. Correct classification according to the different cut-off points obtained via polysomnography and the corresponding cut-off points in the MERLIN manual index were confirmed in 90-96% of patients. The MERLIN device is a useful diagnostic approach for the initial assessment of adult patients with clinical suspicion of sleep apnoea/hypopnoea syndrome. Manual scoring is clearly better than automatic scoring in terms of agreement with the apnoea/hypopnoea index and to discern patients with sleep apnoea/hypopnoea syndrome.