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To the Editor.—
Sanders et al1 reported the "saw-tooth" sign of the flow-volume loop as indicating a likelihood of significant sleep-associated upper airway obstruction (UAO). They emphasized well-defined, regular oscillations occurring at constant intervals on forced expiratory and/or inspiratory flow-volume tracings as a phenomenon attributable to structural or functional abnormality in the upper airway. In 21 subjects studied, 13 had sleep apnea hypersomnolence syndrome associated with UAO (SAHS-UAO). Eleven of the 13 patients had "saw-toothing" on the flow-volume loop, which correlated with fluttering of tissue visualized in the upper airway via bronchoscopy. Specificity of the saw-toothing was 100% in their study group, but the authors cautioned in their conclusion that this pattern may simply represent an interplay of physical forces within the upper airway that may or may not have clinical manifestations. We recently saw a patient with a saw-tooth pattern whose clinical status and follow-up study findings question
Kohan JM, Israel RH, Greenblatt DW, Poe RH. 'Saw-Tooth' Pattern on a Flow-Volume Loop Following Neck Surgery. JAMA. 1984;252(19):2701–2702. doi:10.1001/jama.1984.03350190011008
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