title: Faster rise of exhaled breath temperature in asthma: a novel marker of airway inflammation?
abstract: 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 (Deltae degrees T). We measured Deltae degrees T in 18 asthmatic subjects (mean age +/- SEM, 38 +/- 8 yr; 9 male, FEV(1) 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. Deltae degrees 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 degrees C and 34.45 +/- 0.8 degrees C, p > 0.05). However, Deltae degrees T was greater in asthmatic subjects (8.17 +/- 0.83 degrees C/s and 4.12 +/- 0.41 degrees C/s, p < 0.01) and correlated with NO (r = 0.65, p = 0.034). Deltae degrees T was increased in normal subjects (from 4.28 +/- 0.8 degrees C/s to 7.60 +/- 0.5 degrees C/s, p < 0.01) but not in asthmatic patients (from 8.28 +/- 0.41 degrees C/s to 8.80 +/- 0.41 degrees C/s, p > 0.05) after the inhalation of albuterol, indicating that Deltae degrees T may reflect bronchial blood flow. Asthmatic subjects have elevated Deltae degrees T. This may represent a novel, noninvasive means of measuring airway blood flow and inflammation in asthma.
authors.affiliation: Department of Thoracic Medicine, National Heart and Lung Institute, Imperial College School of Science, Technology and Medicine, London, United Kingdom.
authors.forename: Paolo
authors.initials: P
authors.lastname: Paredi
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Kharitonov
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barnes
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology; D001249:Asthma / Q000503:physiopathology*; D015415:Biomarkers; D001944:Breath Tests / Q000379:methods; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D007249:Inflammation / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis; D011652:Pulmonary Circulation / Q000502:physiology; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology; D020545:Respiratory Mucosa / Q000503:physiopathology; D013696:Temperature
chemical_list: D015415:Biomarkers; D009569:Nitric Oxide