Am. J. Respir. Crit. Care Med., Volume 165, Number 2, January 2002, 181-184

Faster Rise of Exhaled Breath Temperature in Asthma
A Novel Marker of Airway Inflammation?

PAOLO PAREDI, SERGEI A. KHARITONOV, and PETER J. BARNES

Department of Thoracic Medicine, National Heart and Lung Institute, Imperial College School of Science, Technology and Medicine, London, United Kingdom

In asthma there is increased vascularity of the airway mucosa, altering heat loss in the airways. We hypothesized that as a result of these inflammatory changes, asthmatic patients would have elevated rates of the exhaled air temperature increase (e°T). We measured e°T in 18 asthmatic subjects (mean age ± SEM, 38 ± 8 yr; 9 male, FEV₁ 74 ± 10%) and 16 normal volunteers (mean age ± SEM, 33 ± 3 yr) and compared it with exhaled nitric oxide (NO) as a marker of inflammation. e°T was measured during a flow- and pressure-controlled single exhalation with a fast response (1 ms) thermometer. The end-expiratory plateau temperature was similar in asthmatic compared with normal subjects (35.75 ± 0.6° C and 34.45 ± 0.8° C, p > 0.05). However, e°T was greater in asthmatic subjects (8.17 ± 0.83° C/s and 4.12 ± 0.41° C/s, p < 0.01) and correlated with NO (r = 0.65, p = 0.034). e°T was increased in normal subjects (from 4.28 ± 0.8° C/s to 7.60 ± 0.5° C/s, p < 0.01) but not in asthmatic patients (from 8.28 ± 0.41° C/s to 8.80 ± 0.41° C/s, p > 0.05) after the inhalation of albuterol, indicating that e°T may reflect bronchial blood flow. Asthmatic subjects have elevated e°T. This may represent a novel, noninvasive means of measuring airway blood flow and inflammation in asthma.

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