Exhaled Breath Temperature in COPD

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. Identifying patients with early COPD remains challenging; however, even at this stage, substantial biological disease progression and irreversible lung injury may already be present. Considerable effort has therefore been directed toward identifying parameters that detect early pathophysiological changes before airflow limitation develops. The importance of this stage has recently been recognized and is described using terms such as "pre-COPD" and "early COPD". Exhaled breath temperature (EBT) is a non-invasive method for detecting and monitoring respiratory inflammation. Most EBT studies have been conducted in asthma and have demonstrated the utility of this approach for assessing changes in airway inflammation. In patients with COPD, the number of airways and their vasculature is reduced, and EBT decreases proportionally with the degree of structural destruction; however, EBT may still increase during COPD exacerbations. In recent studies, the change in EBT after cigarette smoking in individuals without a COPD diagnosis significantly predicted disease progression after 2 years. Early interventions based on these findings should be tested for efficacy in preventing the development of overt COPD.