Pulmonary gas exchange is reduced by the cardiovascular diving response in resting humans

The diving response reduces the pulmonary O(2) uptake in exercising humans, but it has been debated whether this effect is present at rest. Therefore, respiratory and cardiovascular responses were recorded in 16 resting subjects, performing apnea in air and apnea with face immersion in cold water (10 degrees C). Duration of apneas were predetermined to be identical in both conditions (average: 145 s) and based on individual maximal capacity (average: 184 s). Compared to apnea in air, an augmented diving response was elicited by apnea with face immersion. The O(2) uptake from the lungs was reduced compared to the resting eupneic control (4.6 ml min(-1)kg(-1)), during apnea in air (3.6 ml min(-1)kg(-1)) and even more so during apnea with face immersion (3.4 ml min(-1)kg(-1)). We conclude that the cardiovascular adjustments of the diving response reduces pulmonary gas exchange in resting humans, allowing longer apneas by preserving the lungs' O(2) store for use by vital organs.