Cerebrospinal fluid acid-base balance during a changing ventilatory state in man

Comparison of the rate and magnitude of changes in pH, CO 2 tension, and bicarbonate concentration in arterial blood, cisternal spinal fluid, and lumbar spinal fluid was made in man during hyperventilation and recovery. CO 2 tension changes in cisternal fluid were rapid and significant, although less in magnitude than those in arterial blood, whereas changes in lumbar fluid CO 2 tension were minimal and slow, lagging behind cisternal changes by 10–20 min. The different rates of change following altered ventilation explain some of the reported reversals of the normal lumbar spinal fluid to arterial blood CO 2 tension gradients. It also suggests that the choroid plexus is one site of removal of CO 2 from spinal fluid. Submitted on December 13, 1962