1. Rapid intravenous (i.v.) infusions of saline were administered to five healthy male volunteers. Measurements were made of static and dynamic lung volumes, ‘closing volume’ and pulmonary compliance before and after infusion; all measurements were made in the seated upright position.
2. Following a 1 litre infusion small decreases occurred in static and dynamic lung volumes in all studies and were associated in each case with an increase in ‘closing volume’. ‘Closing volume’ returned to normal within 1 h of the infusion.
3. After 2 litre infusions more marked decreases in all lung volumes occurred and were associated with variable changes in ‘closing volume’. The pattern of change varied between individual subjects and this is thought to reflect differences in localization within the lungs of the effects of the saline load in different subjects.
4. After 2 litre infusions static compliance was decreased in all subjects during the first 10–15 min. Changes in dynamic compliance showed marked individual variation.