Comparison of exhaled breath condensate pH using two commercially available devices in healthy controls, asthma and COPD patients

Rembert Koczulla, Silvano Dragonieri, Robert Schot, Robert Bals, Stefanie A Gauw, Claus Vogelmeier, Klaus F Rabe, Peter J Sterk, Pieter S Hiemstra, Rembert Koczulla, Silvano Dragonieri, Robert Schot, Robert Bals, Stefanie A Gauw, Claus Vogelmeier, Klaus F Rabe, Peter J Sterk, Pieter S Hiemstra

Abstract

Background: Analysis of exhaled breath condensate (EBC) is a non-invasive method for studying the acidity (pH) of airway secretions in patients with inflammatory lung diseases.

Aim: To assess the reproducibility of EBC pH for two commercially available devices (portable RTube and non-portable ECoScreen) in healthy controls, patients with asthma or COPD, and subjects suffering from an acute cold with lower-airway symptoms. In addition, we assessed the repeatability in healthy controls.

Methods: EBC was collected from 40 subjects (n = 10 in each of the above groups) using RTube and ECoScreen. EBC was collected from controls on two separate occasions within 5 days. pH in EBC was assessed after degasification with argon for 20 min.

Results: In controls, pH-measurements in EBC collected by RTube or ECoScreen showed no significant difference between devices (p = 0.754) or between days (repeatability coefficient RTube: 0.47; ECoScreen: 0.42) of collection. A comparison between EBC pH collected by the two devices in asthma, COPD and cold patients also showed good reproducibility. No differences in pH values were observed between controls (mean pH 8.27; RTube) and patients with COPD (pH 7.97) or asthma (pH 8.20), but lower values were found using both devices in patients with a cold (pH 7.56; RTube, p < 0.01; ECoScreen, p < 0.05).

Conclusion: We conclude that pH measurements in EBC collected by RTube and ECoScreen are repeatable and reproducible in healthy controls, and are reproducible and comparable in healthy controls, COPD and asthma patients, and subjects with a common cold.

Figures

Figure 1
Figure 1
Effect of duration of degasification on fresh and frozen EBC samples. EBC samples collected by RTube were obtained from 5 healthy controls, and either used fresh or after storage at -20°C (frozen). Prior to pH analysis, EBC samples were de-aerated using argon gas for various periods of time. Results show mean ± SD.
Figure 2
Figure 2
Bland-Altman plot showing within-subject repeatability of pH in EBC collected by ECoScreen (Figure 2A) and RTube (Figure 2B) from 10 healthy subjects on two different days. Horizontal lines show the mean and 95% confidence interval.
Figure 3
Figure 3
Comparison of pH in EBC obtained by either RTube or ECoScreen in healthy controls (HC), asthma, COPD and cold patients (n = 40). The dashed line is the line of identity.
Figure 4
Figure 4
Bland-Altman plot showing good agreement between pH values in EBC collected from 10 healthy subjects using ECoScreen and RTube on two different days. Horizontal lines show the mean and 95% confidence interval.
Figure 5
Figure 5
Bland-Altman plot showing good agreement between pH values in EBC collected by ECoScreen and RTube from patients with asthma, COPD or a cold (n = 10 for each group). Horizontal lines show the mean and 95% confidence interval.
Figure 6
Figure 6
Comparison of EBC pH values obtained by ECoScreen (left panel) or RTube (right panel) in healthy controls, and patients with asthma, COPD or a cold (n = 10 per group). Using both devices, pH values in patients with a cold were significantly lower than in healthy controls, whereas the other patient groups did not show a difference.

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