Flow-volume curves and sleep-disordered breathing: therapeutic implications.

To assess the relationship of abnormal flow-volume curves during awake periods to the clinical severity of sleep-disordered breathing and the need for surgical treatment of obstructive sleep apnoea, flow-volume curves were measured in 72 adults with obstructive apnoea. Patients in whom surgery was recommended for standard clinical indications had significantly lower inspiratory flow rates (p less than 0.01) and a higher incidence of flow-volume curves indicating extrathoracic airway obstruction (p less than 0.01) than did non-surgical patients. These abnormal flow-volume curves correlated with an increased severity of nocturnal oxygen desaturation (p less than 0.01). Furthermore, increases in inspiratory flow rates measured serially in 22 patients were related to improvement in their polysomnography (p less than 0.05), suggesting that alterations of airway function during awake periods correlate with changes in the severity of sleep apnoea.