HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS REGISTER		Author Keyword(s) Vol Page [Advanced]

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this link to a friend Similar articles in this journal Similar articles in PubMed Add article to my folders Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wells, K Articles by Hunt, J Search for Related Content PubMed PubMed Citation Articles by Wells, K Articles by Hunt, J

Exhaled breath condensate pH assays are not influenced by oral ammonia

¹ Division of Pediatric Respiratory Medicine, University of Virginia, USA
² Division of Pediatric Infectious Disease, University of Virginia, USA
³ Division of Neuroanesthesiology, University of Virginia, USA

Correspondence to:
Correspondence to:
Dr J Hunt
Assistant Professor of Pediatric Allergy, Immunology and Pulmonology, Division of Pediatric Respiratory Medicine, Box 800386, University of Virginia, Charlottesville, VA 22908, USA; JHunt{at}virginia.edu

Background: Measurement of pH in exhaled breath condensate (EBC) is robust and simple. Acidic source fluid (airway lining fluid) traps bases while volatilising acids, leading to EBC acidification in many lung diseases. Lower airway ammonia is one determinant of airway lining fluid pH, raising the concern that addition of the base ammonia by contamination from the mouth might confound EBC pH assays.

Methods: Three discrete methods were used to limit oral ammonia contamination of EBC collections: endotracheal intubation, oral rinsing, and –40°C condenser temperatures. Separately, ammonia was removed from collected EBC samples by lyophilisation and resuspension. Intraweek and intraday variability of ammonia concentration was determined in 76 subjects, and ammonia and pH from a further 235 samples were graphically compared. Ammonia was assayed spectrophotometrically and pH was assessed after deaeration.

Results: Data from 1091 samples are presented. Ammonia was reduced in EBC by all methods. Endotracheal intubation decreased EBC ammonia from a mean (SD) of 619 (124) µM to 80 (24) µM (p<0.001, n = 32). Oral rinsing before collection also led to a decline in EBC ammonia from 573 (307) µM to 224 (80) µM (p = 0.016, n = 7). The colder the condensation temperature used, the less ammonia was trapped in the EBC. Lyophilisation removed 99.4 (1.9)% of ammonia. Most importantly, the pH of EBC never decreased after removal of ammonia by any of these methods. Intraweek and intraday coefficients of variation for ammonia were 64 (27)% and 60 (32)%, which is substantially more variable than EBC pH assays.

Conclusions: Although ammonia and pH appear to correlate in EBC, the oral ammonia concentration is not an important determinant of EBC pH. No precautions need to be taken to exclude oral ammonia when EBC pH is of interest. The low pH and low ammonia found in EBC from patients with lung diseases appear to be independent effects of volatile compounds arising from the airway.

Keywords: ammonia; exhaled breath condensate; pH

This article has been cited by other articles:

				Z. L. Borrill, K. Roy, and D. Singh Exhaled breath condensate biomarkers in COPD Eur. Respir. J., August 1, 2008; 32(2): 472 - 486. [Abstract] [Full Text] [PDF]

				T. Kullmann, I. Barta, Z. Lazar, B. Szili, E. Barat, M. Valyon, M. Kollai, and I. Horvath Exhaled breath condensate pH standardised for CO2 partial pressure Eur. Respir. J., March 1, 2007; 29(3): 496 - 501. [Abstract] [Full Text] [PDF]

				R. M. Effros, R. Casaburi, J. Su, M. Dunning, J. Torday, J. Biller, and R. Shaker The Effects of Volatile Salivary Acids and Bases on Exhaled Breath Condensate pH Am. J. Respir. Crit. Care Med., February 15, 2006; 173(4): 386 - 392. [Abstract] [Full Text] [PDF]

				A. O. Paget-Brown, L. Ngamtrakulpanit, A. Smith, D. Bunyan, S. Hom, A. Nguyen, and J. F. Hunt Normative Data for pH of Exhaled Breath Condensate. Chest, February 1, 2006; 129(2): 426 - 430. [Abstract] [Full Text] [PDF]

				ATS Workshop Proceedings: Exhaled Nitric Oxide and Nitric Oxide Oxidative Metabolism in Exhaled Breath Condensate. Proceedings of the ATS, January 1, 2006; 3(2): 131 - 145. [Full Text] [PDF]

				I. Horvath, J. Hunt, P. J. Barnes, and On behalf of the ATS/ERS Task Force on Exhaled Bre Exhaled breath condensate: methodological recommendations and unresolved questions Eur. Respir. J., September 1, 2005; 26(3): 523 - 548. [Abstract] [Full Text] [PDF]

				G. MacGregor, S. Ellis, J. Andrews, M. Imrie, A. Innes, A. P. Greening, and S. Cunningham Breath condensate ammonium is lower in children with chronic asthma Eur. Respir. J., August 1, 2005; 26(2): 271 - 276. [Abstract] [Full Text] [PDF]