Airflow dynamics and exhaled-breath temperature following cold-water ingestion

Introduction. Drinking cold water evokes decreases in spirometric indices of lung function. We studied whether this could be explained by changes in exhaled-breath temperature (EBT), airflow dynamics,and spirometer measurement sensitivity. Methods. In a randomized/crossover design, 10 healthy adults consumed 1,000 mL refrigerated water (2.1±0.64 ºC) or water at room temperature (19.4±0.5 ºC), with EBT assessed at baseline and at 5,10,15 and 30-min post-ingestion. The influence of EBT on pneumotachograph measurement characteristics was modelled using computational fluid dynamics (CFD). Results. At 5-min post-ingestion, EBT was lower (p<0.001) following the ingestion of cold water versus water at room-temperature (31.7±1.1 vs. 33.0±0.9 °C), and remained lower until 30-min post-ingestion. At a flow of 8 L*s−1 , a decrease in EBT of 2.1 ° 29 C (observed following cold-water ingestion) was modelled to underpredict lung volume by 0.7%. Conclusions. Cold water reduces EBT below baseline but effects pneumotachograph measurements only negligibly; thus, decreased lung function following cold-water ingestion likely has a physiological explanation which warrants further study