Lack of effect of hydration on sputum production in chronic bronchitis

Patients with chronic lung disease productive of sputum are generally encouraged to drink a large amount of fluid to facilitate sputum production. This clinical practice has not been tested systematically. Twelve outpatients with chronic obstructive pulmonary disease in clinically stable condition who had daily sputum production were asked in random sequence: 1) to drink one glass of fluid every waking hour after supper and upon waking the next morning (hydration), 2) to drink no fluid after supper and upon waking the next morning (dry), and 3) to drink fluid ad lib (ad lib). Each morning sputum collection was started upon waking and continued for four hours. The differences in volume, elasticity of sputum, respiratory symptoms, and ease of expectoration were not significant. We conclude that moderate hydration and dehydration have no effect on volume expectorated, the elasticity of sputum, respiratory symptoms or forced expiratory volume in one second.