Exhaled breath temperature increases after exercise in asthmatics and controls

Background: Exhaled breath temperature (EBT) has been suggested as a marker of airway inflammation in asthma. Objectives: The aim of the present study was to investigate EBT in asthmatic subjects compared to healthy controls after an exercise challenge test, and in subjects with exercise-induced bronchoconstriction compared to subjects without, and to compare with body temperatures. Methods: A total of 21 healthy controls and 20 asthmatics were included. Forced expiratory volume in 1 s (FEV(1)), EBT and oral, axillary and auricular temperatures were measured before and after an exercise challenge test. Results: FEV(1) % predicted (%p) was significantly lower in asthmatic subjects compared to healthy controls at all time points after exercise. The largest drop in FEV(1)%p correlated with EBT after 5 min. EBT increased markedly 5 min after exercise and remained high for at least 60 min. In asthmatics whose FEV(1) dropped by >10%, EBT was higher after 60 min compared to the remaining asthmatics. EBT correlated with oral temperature at all time points after exercise, with axillary temperature only at 15, 30 and 60 min, and not at all with auricular temperature. Conclusions: EBT is increased after exercise, and elevated EBT correlated with a drop in FEV(1)%p. The immediate increase in EBT did not differ between asthmatics and controls but remained elevated in the asthmatics whose FEV(1) dropped by >10%, indicating a different vascular response.