VALIDATION OF BRITISH-THORACIC-SOCIETY GUIDELINES FOR THE DIAGNOSIS OF THE SLEEP-APNEA HYPOPNEA SYNDROME - CAN POLYSOMNOGRAPHY BE AVOIDED

Background-The British Thoracic Society report on the diagnosis and tr eatment of the sleep apnoea/hypopnoea syndrome (SAHS) suggests that, i f the pulse oximetry baseline oxygen saturation is above 90%, then 15 4% oxygen desaturations/hour in bed will diagnose SAHS requiring treat ment. The diagnostic outcome of applying these guidelines has been stu died. Methods - One hundred patients referred to a district general ho spital sleep clinic were recruited. After initial clinical assessment, overnight pulse oximetry measurements were performed, followed by ful l polysomnography at the regional laboratory. Results - Sixty nine pat ients underwent both pulse oximetry and polysomnography. All 10 patien ts with more than 15 4% desaturations/hour on pulse oximetry had SAHS confirmed on polysomnography (specificity = 100%). Twenty two patients with SANS were misdiagnosed using pulse oximetry alone (sensitivity = 31%). These patients had low apnoea scores but high hypopnoea scores. Conclusions - The BTS pulse oximetry criteria are highly specific whe n positive (specificity = 100%), but may miss patients with the SAHS w ho have hypopnoeic episodes which cause arousal but not significant ox ygen desaturation (sensitivity = 31%). It should be emphasised that pu lse oximetry alone does not always give sufficient information to disc riminate between those patients with or without SAHS. Patients with '' negative'' pulse oximetry and symptoms of SAHS should undergo polysomn ography or multi-channel recording.