Pathologic A waves

Interpreting ICP waveforms: A waves. The most clinically significant ICP waveforms are A waves, which may reach elevations of 50 to 100 mm Hg, persist for 5 to 20 minutes, then drop sharply - signaling exhaustion of the brain's compliance mechanisms. A waves may come and go, spiking from temporary rises in thoracic pressure or from any condition that increases ICP beyond the brain's compliance limits. Activities, such as sustained coughing or straining during defecation, can cause temporary elevations in thoracic pressure.