Changes in arterial plasma potassium and ventilation during exercise in man.

We have investigated the relationship between arterial plasma potassium ( [K+]a) and ventilation (VE) in man because hyperkalaemia has been shown to increase VE in the anaesthetized cat by direct stimulation of the arterial chemoreceptors. Six healthy male volunteers undertook about of sub-maximal (100 W) and maximal (sprint ca. 350 W) exercise on a cycle ergometer. VE 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 VE 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 VE in that it reached its nadir 1-3 min after exercise had stopped, when [K+]a and VE 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 VE suggests that it is possible that exercise hyperkalaemia may contribute to the control of breathing in exercise.