Relationship Between Respiration and Pressure Wave: An experimental study in kaolin-induced hydrocephalus

Abstract

Plateau waves often are observed in patients with “normal pressure hydrocephalus” during continuous monitoring of intracranial pressure (ICP). An experiment was performed to determine whether respiratory changes cause plateau waves in patients with hydrocephalus and normal ICP. Twelve adult mongrel dogs were immobilized and ventilated mechanically. Hypoventilation for ten minutes was induced by decreasing both the tidal volume and the respiratory rate to half those of normal ventilation, and then normal ventilation was resumed. The dogs were divided into three groups; Control group, 4 dogs (Group C); Kaolin-induced hydrocephalus group, in which the ICP had returned to the normal range in chronic stage, 4 dogs (Group K); and, for the purpose of comparison to Group K, an extradural balloon-inflated group in which the ICP was within the normal range, 4 dogs (Group B). During hypoventilation, the level of increased ICP was higher, and in response to changes in ICP, cerebral perfusion pressure (CPP) was decreased significantly more in Group K and Group B than in Group C. The increase in ICP persisted during hypoventilation, as do plateau waves. None of the parameters monitored showed any statistically significant difference between Group K and Group B, therefore the response of ICP in these two groups probably is similar for the same respiratory changes.