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Exhaled Breath Condensate pH and Childhood Asthma

Unselected Birth Cohort Study

University of Manchester; and North West Lung Centre, Wythenshawe Hospital, Manchester, United Kingdom

Correspondence and requests for reprints should be addressed to Nicolaos Nicolaou, M.D., North West Lung Centre, Wythenshawe Hospital, Manchester M23 9LT, UK. E-mail: nicolaos.nicolaou{at}postgrad.manchester.ac.uk

Rationale: Exhaled breath condensate pH (EBC-pH) may be useful noninvasive marker for evaluation of patients with asthma.

Objectives: To investigate the relationship between EBC-pH and symptoms suggestive of childhood asthma in an epidemiologic setting and examine its relation to lung function, airway hyperresponsiveness (AHR), and airway inflammation.

Methods: Within the context of a prospective population-based birth cohort, EBC was collected from 630 children at age 8 yr using the RTube (pH measured after deaeration with argon). Lung function was measured by spirometry (FEV₁; n = 521) and plethysmography (sRaw; n = 567), and AHR by methacholine challenge (n = 498). Airway inflammation was assessed using exhaled nitric oxide (eNO; n = 305).

Results: EBC-pH values ranged widely (4.40–8.29), and did not differ between 54 children with parentally reported asthma and 562 nonasthmatic subjects (median [interquartile range]: 7.75 [7.45–7.85] vs. 7.77 [7.59–7.87]; p = 0.35). There was a trend for lower EBC-pH among current wheezers (n = 98; 7.72 [7.50–7.83]) compared with nonwheezers (n = 532; 7.77 [7.60–7.87]; p = 0.07). Wheeze frequency, severity, and use of antiasthma medication were not associated with EBC-pH. There was no consistent association between EBC-pH and lung function, airway reactivity, and airway inflammation (FEV₁, sRaw, PD₂₀ methacholine, or eNO). There was no significant difference in EBC-pH between current wheezers receiving asthma medication who had positive methacholine challenge compared with children without any of these features.

Conclusions: In the epidemiologic setting, EBC-pH does not differ between children with and without parentally reported symptoms suggestive of asthma. We found no consistent association between EBC-pH and lung function, AHR, and airway inflammation in this sample from the general population.

Key Words: airway acidity • asthma • exhaled breath condensate • lung function

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