Exhaled breath condensate pH as a biomarker of COPD severity in ex-smokers

Andriana I Papaioannou,Petros Bakakos,Spyros Papiris,Markos Minas,Konstantina Kontogianni,Konstantinos Kostikas,Manos Alchanatis,Konstantinos I Gourgoulianis,Stelios Loukides

doi:10.1186/1465-9921-12-67

Andriana I Papaioannou, Petros Bakakos + Show 7 more

Open Access

https://doi.org/10.1186/1465-9921-12-67

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Abstract

Endogenous airway acidification, as assessed by exhaled breath condensate (EBC) pH, is present in patients with stable COPD. The aim of this study was to measure EBC pH levels in a large cohort of COPD patients and to evaluate associations with functional parameters according to their smoking status.EBC was collected from 161 patients with stable COPD and 112 controls (current and ex-smokers). EBC pH was measured after Argon deaeration and all subjects underwent pulmonary function testing.EBC pH was lower in COPD patients compared to controls [7.21 (7.02, 7.44) vs. 7.50 (7.40, 7.66); p < 0.001] and ex-smokers with COPD had lower EBC pH compared to current smokers [7.16 (6.89, 7.36) vs 7.24 (7.09, 7.54), p = 0.03]. In ex-smokers with COPD, EBC pH was lower in patients with GOLD stage III and IV compared to patients with stage I disease (p = 0.026 and 0.004 respectively). No differences were observed among current smokers with different disease severity. EBC pH levels in ex-smokers were associated with static hyperinflation (as expressed by IC/TLC ratio), air trapping (as expressed by RV/TLC ratio) and diffusing capacity for carbon monoxide, whereas no associations were observed in current smokers.Endogenous airway acidification is related to disease severity and to parameters expressing hyperinflation and air trapping in ex-smokers with COPD. The possible role of EBC pH in COPD needs to be further evaluated in longitudinal studies.

Highlights

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible, is usually progressive, and is associated with an abnormal inflammatory response of the lungs in response to noxious particles and gases [1]
Patients with COPD and controls did not differ in age, gender and smoking habit; ex-smokers with COPD had significantly lower FEV1, FEV1/FVC and DLCO compared to current smokers
No differences were observed among COPD current smokers with different disease severity (Figure 2B)

Summary

Introduction

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible, is usually progressive, and is associated with an abnormal inflammatory response of the lungs in response to noxious particles and gases [1]. It has been postulated that acidification of the exhaled air may be a surrogate marker of airway inflammation in COPD [4]. In support of this hypothesis we have. The aim of the present study was to evaluate EBC pH levels in a large cohort of COPD patients with different disease severity and to compare them with smoking controls matched for age, gender and smoking habit. Associations of EBC pH values with functional parameters, including parameters expressing static hyperinflation and air-trapping, were evaluated. Those associations were further analyzed according to the smoking status of COPD patients (current vs ex-smokers)

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