Conventional PFTs are generally regarded as unhelpful in providing clues to the diagnosis of OSA; however, alterations in the flow-volume relationship have been reported in OSA, including elevation of the ratio of FEF50%/FIF50% and a sawtooth appearance of the expiratory or inspiratory limbs (or both) of the flow-volume loop. These abnormalities have been attributed to variable extrathoracic airway obstruction and “fluttering” of pharyngeal tissue, respectively. Their reported sensitivity and specificity have varied greatly in different reports, resulting in little enthusiasm for using the flow-volume loop to identify patients with OSA. Most studies evaluating the sensitivity and specificity of PFTs in OSA have not used control subjects matched for age, weight, and gender who were proven to have little or no sleep- disordered breathing. This is an issue of some concern, as several reports demonstrate sleep-disordered breathing in asymptomatic men.
We recently reported that overweight men with severe OSA have higher Rp during wakefulness than control subjects matched for age and weight, even though the static PCSA at FRC is not significantly smaller. The present study evaluates PFTs in patients with documented OSA and matched control subjects in order to determine whether alterations in pharyngeal resistance and size are associated with the flow- volume relationship and other measurements of pulmonary function.
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