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 > or = 5, 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.