Abstract

Alteration in heart rate and respiratory rate and depth occurred in association with intracranial pressure (ICP) waves in 27 patients with head injuries. Usually the ICP wave was preceded by a transient increase in end-alveolar CO2 levels. Thereafter, the ICP gradually increased and was accompanied by simultaneous decreases in heart rate and respiratory rate and depth. Immediately before the termination of the ICP wave, there was an abrupt increase in heart rate and respiratory rate and depth. After the ICP fell to base line level, heart rate and respiration returned to control values. It is suggested that the transient alterations in the CO2 level at the beginning and during the ICP wave probably initiate these abnormal waves. While the heart rate changes are striking, their role in the formation and termination of ICP pressure waves is uncertain.