Currently, there is uncertainty regarding the effects of systemic dehydration on pulmonary function.

The goals of a new study published in the Journal of Applied Physiology was to clarify the impact of exercise- or fluid restriction-induced dehydration on pulmonary function in healthy adults; to establish whether systemic or local rehydration can reverse dehydration-induced alterations in pulmonary function. 

This study recruited ten healthy participants who performed four experimental trials in a randomized order – 2 hours of exercise in the heat twice, and 28 hours of fluid restriction twice. Pulmonary function was assessed using spirometry and whole-body plethysmography in the euhydrated, dehydrated, and rehydrated states. Oral fluid consumption was used for systemic rehydration and nebulized isotonic saline inhalation for local rehydration.

The results showed that both, exercise and fluid restriction induced mild dehydration and elevated plasma osmolality. While dehydration was accompanied by a reduction in forced vital capacity and concomitant increases in residual volume and functional residual capacity, with no statistical differences between modes of dehydration. These changes were normalized by fluid consumption, but not nebulization. 

It was concluded that in healthy adults, mild systemic dehydration induced by exercise or fluid restriction leads to pulmonary function impairment, primarily localized to small airways. While systemic rehydration reverses these potentially deleterious alterations. Oral rehydration is the most effective strategy for reversing dehydration-induced pulmonary impairments.

Source: Journal of Applied Physiology. 2021 Mar 1;130(3):517-527. doi: 10.1152/japplphysiol.00311.2020.