Analysis of epidural pressure pulse wave (EDP-PW) and common carotid blood velocity (CBFV) in acute intracranial hypertension.

The changes in the two consistent components of epidural pressure pulse wave (EDP-PW), P1 and P2 waves, and mean velocity of common carotid blood flow (CBFV) were studied in 21 patients with acute intracranial hypertension to investigate the origin of th the amplitude change in these components. The amplitudes of P2 wave increased progressively with the rise of EDP, but those of P1 wave remained nearly invariable at EDP of more than 20-30 mmHg which is incompatible with the changes in CBFV. Jugular vein compression caused in rapid rise of EDP and a proportionate increase in the magnitudes of both waves. Hyperventilation and mannitol administration caused a disproportionate reduction in the amplitudes of P2 wave with a fall of EDP. But mannitol at high EDP (more than 40 mmHg) caused a mild fall of EDP and some increase in the amplitudes of P2 wave. These results indicate that the variations in the amplitudes of P1 wave reflect the changes in vascular resistance of the large intracranial conductive arteries, while those of P2 wave result from the changes in the volume of the cerebral bulk. The increase in the amplitudes of P2 wave induced by mannitol at high EDP may suggest a defective autoregulation of the cerebral vessels.