Airway cell patterns in patients suffering from COPD and OSAS (Overlap Syndrome)

Background: Obstructive sleep apnea syndrome (OSAS) and chronic obstructive pulmonary disease (COPD) are two diseases that often coexist within an individual. This coexistence is known as Overlap Syndrome (OS). Both diseases are characterized by local and systemic inflammations, but no studies to date have investigated local airway inflammation in patients suffering from Overlap Syndrome. Methods: We performed a Berlin Questionnaire to evaluate the presence of the principal OSAS symptoms, a pulmonary function test, and then a nocturnal oximetry and polysomnography in 72 patients that were divided into five groups: OS (n = 18), COPD (n = 15), OSAS (n = 16), 12 obese without OSAS or COPD, and one control group of 11 normal subjects. All patients underwent sputum induction and the analysis of cell patterns were evaluated in all groups. The relationship with the degree of obesity, airway obstruction and OSAS severity was also evaluated. Results: The percentage of neutrophils in induced sputum was higher in OS (74.33% ± 14.8), COPD (63.33% ± 13.22) and OSAS (60.69% ± 17.6) subjects compared with control groups of obese (43.5% ± 17.49) and normal weight (32.04% ± 12.26). No difference was found among Overlap, COPD, and OSAS patients (p = 0.56). A negative correlation was found between PaO₂ and percentage of airway neutrophils (r = -0.29, p <0.05); similarly, no correlations arose between BMI, FEV ₁ or ODI. Conclusion: Patients suffering from Overlap Syndrome present a high percentage of neutrophils in induced sputum like patients affected by COPD or OSAS alone. Our result suggests that airway inflammations is always involved in all of these diseases, even though probably sustained by different mechanisms.