Validation of the exhaled breath temperature measure: reference values in healthy subjects

BACKGROUND: Exhaled breath temperature (EBT) is a new non-invasive method for the study of inflammatory respiratory diseases with a potential to reach clinical practice. However, few studies, and mainly derived from small, paediatric populations, are available on the validation of the method and the range of normal values is not well established. The aim of this study was to measure EBT values in an Italian population of 298 (45.2±15.5 yrs, 143 male, FEV1 97.2±5.8%, FVC 98.4±3.9%) selected from 867 adult volunteers, in order to define reference values in healthy subjects and to analyse the influence of individual and external variables on this parameter. METHODS: We measured EBT with a X-halo PRO device to different ambient temperature that ranged from 0 to 38°C FINDINGS: We report reference value of EBT in healthy Caucasian never smoker subjects. EBT values are strongly influenced by the external temperature and to a lesser extent by gender. INTERPRETATION: These data provide reference values in a large population of healthy never smokers subjects for measuring EBT as a basis for future studies. Our results are a contribution to the promotion of the EBT from bench to bed side.