Changes in arterial plasma potassium and ventilation during exercise in man

Abstract

We have investigated the relationship between arterial plasma potassium ([K+]a) and ventilation (V̇e) in man because hyperkalaemia has been shown to increase V̇e in the anaesthetized cat by direct stimulation of the arterial chemoreceptors. Six healthy male volunteers undertook a bout of sub-maximal (100 W) and maximal (sprint ca. 350 W) exercise on a cycle ergometer. V̇e was measured breath-by-breath and arterial blood was sampled at regular intervals from a catheter inserted into a brachial artery for measurement of [K+]a and base excess. Changes in [K+a closely mirrored changes in V̇e during exercise and recovery. At 100 W [K+]a increased from 4 mM to 5 mM, and during the sprint [K+]a increased to ca. 7 mM. Base excess did not mirror V̇e in that it reached its nadir 1–3 min after exercise had stopped, when [K+]a and V̇e were both falling. The increases in [K+]a seen here are probably sufficient to enhance the arterial chemoreceptor drive during exercise. Furthermore, the close temporal relationship between [K+]a and V̇e suggests that it is possible that exercise hyperkalaemia may contribute to the control of breathing in exercise.