Abstract
Background: Evaluation of the exhaled breath temperature (EBT) has been suggested as surrogate biomarker of airway inflammation, but there is no data on its circadian variation in health and disease. Measuring it by portable handheld device has been proven to be precise and highly reproducible. The aim of the study was to identify peaks and troughs in EBT around the clock in healthy individuals.
Methods: Forty two subjects (24 women; median age 26 years, age range 3 to 80 years) without history and objective signs of respiratory disease volunteered for the study. Subjects and/or their parents were trained to measure EBT with a portable hanheld device (X-halo, Delmedica, Singapore). They took it home and were instructed to do measurements at four time points (±30 min.): 7, 13, 19 and 1 hours (h). All values were stored in the memory of the devices and were subsequently retrieved and analyzed by the research team. Axillary temperature (AxT) was measured and analyzed in parallel.
Results: EBT values showed a circadian pattern different from the one of AxT: the acrophase (peak temperature) was registered at 19 h for EBT and at 13 h for AxT. The bathyphase (trough temperature) was the same for both circadian rhythms at 1 h. Repeated measures analysis found both circadian fluctuations to be statistically significant (table):
Conclusions: Healthy subjects EBT have a different circadian course during the day and night compared with AxT. EBT circadian influences need also to be identified in inflammatory airway diseases.
- © 2011 ERS
