Expiratory Snoring Predicts Obstructive Pulmonary Disease in Patients with Sleep-disordered Breathing

Rationale: Sleep-disordered breathing and chronic obstructive pulmonary disease are two common conditions that may present concomitantly. The effects of chronic obstructive pulmonary disease on the polysomnographic manifestation of sleep-disordered breathing have not been studied.

Objectives: We hypothesized that the presence of airflow obstruction could be predicted by the presence of expiratory upper airway narrowing during sleep in patients with sleep-disordered breathing.

Methods: Ninety-three patients with sleep-disordered breathing (19 men; age, 51.6 yr; body mass index, 40.1 kg/m(2); apnea-hypopnea index, 37.4 events/h) were observed. Every patient had an in-lab polysomnography study and complete pulmonary function tests. Sleep and respiratory events were scored using American Academy of Sleep Medicine recommended scoring criteria. Expiratory snoring events were identified on polysomnography using microphone sensor and/or pressure flow sensor in each patient. The FEV1/FVC ratio less than 70 was used to define the presence of airflow obstruction.

Measurements and main results: The proportion analysis demonstrated that patients with expiratory snoring have 11 times higher odds of having evidence of lower airway obstruction, defined as FEV1/FVC less than 70 (odds ratio [OR], 11.03; P < 0.001), whereas smokers have increased odds by 13 times (OR, 13.18; P < 0.001). Spearman correlation analysis showed that FEV1 was positively related to mean SaO2 (P < 0.05) and negatively related to expiratory snoring, smoking, 3% oxygen desaturation index, 2% oxygen desaturation index, and age (P < 0.05). Epworth sleepiness scale, sex, and body mass index did not have any association with FEV1. The multiple logistic regression analysis demonstrated that chronic obstructive pulmonary disease (FEV1/FVC < 70) correlated significantly with expiratory snoring and smoking (OR, 11.76; confidence interval, 3.23-42.83; and OR, 9.95; confidence interval, 2.67-37.09), respectively. The multiple linear regression analysis revealed that the linear combination of mean SaO2 and expiratory snoring (P < 0.05) predicted FEV1. However, age and 2% oxygen desaturation index did not predict FEV1.

Conclusions: The presence of expiratory snoring predicts obstructive airway disorders. Patients with expiratory snoring and low mean oxygen saturation during sleep should be carefully assessed for pulmonary disorders such as asthma and chronic obstructive pulmonary disease.