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 spimmeter measurement sensitivity. Methods: In a randomized/crossover design, 10 healthy adults consumed 1000 mL refrigerated water (2.1 +/- 0.64 degrees C) or water at room temperature (19.4 +/- 0.5 degrees C), 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 degrees C), and remained lower until 30-min post-ingestion. At a flow of 8 L s(-1), a decrease in EBT of 2.1 degrees C (as 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. Therefore, decreased lung function following cold-water ingestion likely has a physiological explanation which warrants further study.