The detection of sleep apnea in the awake patient. The 'saw-tooth' sign.

We studied 21 subjects, 13 of whom had the sleep apnea hypersomnolence syndrome associated with upper airway obstruction during sleep (SAHS-UAO) to determine if "saw-toothing" on the flow-volume loop was significantly associated with the phenomenon of airway occlusion during sleep. A "saw-tooth" pattern was present on the flow-volume loop in 11 of 13 subjects with SAHS-UAO. The presence of saw-toothing correlated with fluttering of tissue that was visualized in the upper airway via the fiberoptic bronchoscope. The specificity of the saw-tooth pattern for SAHS-UAO was 100%. Generalized obesity may indirectly influence the presence of saw-toothing due to deposition of what appeared to be adipose tissue in the pharyngeal walls. Although the number of subjects in this study is small, saw-toothing on the flow-volume loop appears to be an important aid in the diagnosis of SAHS-UAO.