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Original Research: ASTHMA |

Determinants of Exhaled Breath Condensate pH in a Large Population With Asthma

Lei Liu, PhD; W. Gerald Teague, MD; Serpil Erzurum, MD; Anne Fitzpatrick, RN, PhD; Sneha Mantri, BA; Raed A. Dweik, MD; Eugene R. Bleecker, MD; Deborah Meyers, PhD; William W. Busse, MD; William J. Calhoun, MD; Mario Castro, MD, FCCP; Kian Fan Chung, MD; Douglas Curran-Everett, PhD; Elliot Israel, MD, FCCP; W. Nizar Jarjour, MD; Wendy Moore, MD, FCCP; Stephen P. Peters, MD, FCCP; Sally Wenzel, MD, FCCP; John F. Hunt, MD; Benjamin Gaston, MD; for the National Heart, Lung, and Blood Institute Severe Asthma Research Program (SARP)
Author and Funding Information

From the Department of Public Health Sciences at the University of Virginia (Dr Liu), and the Department of Pediatrics (Ms Mantri; Drs Hunt and Gaston), Charlottesville, VA; the Department of Pediatrics (Drs Teague and Fitzpatrick), Emory University, Atlanta, GA; the Department of Pathobiology (Drs Erzurum and Dweik) and the Department of Pulmonary, Allergy, and Critical Care Medicine (Drs Erzurum and Dweik), the Cleveland Clinic, Cleveland, OH; the Department of Medicine (Drs Bleecker, Meyers, Moore, and Peters), Wake Forest University, Winston-Salem, NC; the Department of Medicine (Drs Busse and Jarjour), University of Wisconsin, Madison, WI; the Department of Medicine (Dr Calhoun), University of Texas, Galveston, TX; the Department of Medicine (Dr Castro), Washington University, St. Louis, MO; the Imperial College (Dr Chung), London, England; the National Jewish Hospital (Dr Curran-Everett), Denver, CO; the Brigham and Women’s Hospital (Dr Israel), Boston, MA; and the University of Pittsburgh (Dr Wenzel), Pittsburgh, PA.

Correspondence to: Benjamin Gaston, MD, Pediatric Respiratory Medicine, Box 800386, University of Virginia School of Medicine, Charlottesville, VA 22908; e-mail: Bmg3g@virginia.edu


Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

Funding/Support: This work was supported by the National Institutes of Health [Grants NIH/NHLBI: 2RO1, HL 69170 NHLBI Severe Asthma Research Program].

A complete list of study group participants is available in e-Appendix 1.


© 2011 American College of Chest Physicians


Chest. 2011;139(2):328-336. doi:10.1378/chest.10-0163
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Background:  Exhaled breath condensate (EBC) pH is 2 log orders below normal during acute asthma exacerbations and returns to normal with antiinflammatory therapy. However, the determinants of EBC pH, particularly in stable asthma, are poorly understood. We hypothesized that patients with severe asthma would have low EBC pH and that there would be an asthma subpopulation of patients with characteristically low values.

Methods:  We studied the association of EBC pH with clinical characteristics in 572 stable subjects enrolled in the Severe Asthma Research Program. These included 250 subjects with severe asthma, 291 with nonsevere asthma, and 31 healthy control subjects.

Results:  Overall, EBC in this population of stable, treated study subjects was not lower in severe asthma (8.02; interquartile range [IQR], 7.61-8.41) or nonsevere asthma (7.90; IQR, 7.52-8.20) than in control subjects (7.9; IQR, 7.40-8.20). However, in subjects with asthma the data clustered below and above pH 6.5. Subjects in the subpopulation with pH < 6.5 had lower fraction of exhaled NO (FeNO) values (FeNO = 22.6 ± 18.1 parts per billion) than those with pH ≥ 6.5 (39.9 ± 40.2 parts per billion; P < .0001). By multiple linear regression, low EBC pH was associated with high BMI, high BAL neutrophil counts, low prebronchodilator FEV1 ratio, high allergy symptoms, race other than white, and gastroesophageal reflux symptoms.

Conclusion:  Asthma is a complex syndrome. Subjects who are not experiencing an exacerbation but have low EBC pH appear to be a unique subpopulation.

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