Abstract: Abstract: Objective To explore the difference in pulmonary function between overlap syndrome and chronic obstructive
pulmonary disease (COPD) in patients. Methods One-hundred-ninty-four patients came from respiratory department in Tianjin
Medical University General Hospital, from October 2012 to August 2014, were included in this study. After inquisition of medical
history, evaluation of lung function and polysomnography (PSG), patients were divided into overlap syndrome (OS, n=78) group,
COPD group (n=76) and healthy control group (n=40). The indexes of lung function and the pulse oscillation index of pulmonary
function were compared between three groups. Results Values of the peak expiratory flow rate (PEF) and the remaining 75%
FVC when expiratory flow rate (MEF75) were significantly decreased in OS group than those of COPD group (P＜ 0.05). Patients
with sleep apnea hypopnea index (AHI) ≥30 times/h showed significantly decreased MEF25 and the maximum mid expiratory
flow (MMEF) in OS group than those of COPD group (P＜ 0.05). Values of the total impedance (Zrs), the resonant frequency (Fres),
viscosity resistance when oscillation frequency was 5 Hz (R5), R20 were significantly increased in OS group than those of COPD
group (P＜ 0.05). Patients with AHI ≥30 times/h were increased significantly than COPD group in R5-R20 and X5 besides Zrs,
Fres, R5, R20. Conclusion There is more serious airway obstruction in patients with OS than that in patients with COPD. Severe
sleep disordered breathing can aggravate small airway obstruction in patients with COPD

Key words: pulmonary disease, chronic obstructive｜ sleep apnea, obstructive｜ respiratory function tests, airway resis
tance,  overlap syndrome
pulmonary disease, chronic obstructive, sleep apnea, obstructive, respiratory function tests, airway resis
tance, overlap syndrome