FEF(25-75)/FVC measurements and extrathoracic airway obstruction in obstructive sleep apnea patients

The aims of this study were to evaluate patients with obstructive sleep apnea syndrome (OSAS) with regards to dysanapsis (airway size relative to lung size) and to demonstrate the differences between the patients with and without extrathoracic airway obstruction. The study population consisted of 15 patients with OSAS and 14 age and body mass index (BMI) matched control subjects. OSAS patients and control subjects showed similar characteristics in FEV(1), FEV(1)/FVC, FEF(25-75), and FEF(25-75)/FVC ratios. Expiration reserve volume was significantly higher in the control group than in OSAS patients (p<0.01). Six patients exhibited extrathoracic airway obstruction while awake. Of these, three had also a sawtooth pattern in their flow-volume curves. The remaining nine patients had no extrathoracic airway obstruction and had lower apnea-hypopnea indexes (AHI) than the obstruction group (p<0.05). OSAS patients and age- and BMI-matched healthy controls had similar characteristics in terms of dysanapsis. In addition, there was no relation between the FEF(25-75)/FVC ratio and AHI, MinO(2), and MeanO(2). Extrathoracic airway obstruction may be a feature of only severe OSAS patients.