In ICP monitoring, if the P2 wave is higher than the P1 wave, what does this indicate?

• A. The patient has high arterial pressure
• B. There is good ventricular compliance
• C. There is poor ventricular compliance
• D. ICP is normal

Answer: (C)

P2 exceeding P1 on an ICP waveform points to reduced brain compliance. The waveform has P1 as the primary arterial pulse peak and P2 as a secondary peak that reflects the brain’s ability to accommodate changes in volume. In a well‑compliant brain, P1 is greater than P2; the system can absorb small increases in volume without a large rise in pressure. When the brain’s compliance deteriorates, the P2 peak grows and can surpass P1, signaling that the compensatory reserve is exhausted. This means small additional volumes can cause a disproportionate rise in ICP, indicating poor ventricular (intracranial) compliance and a higher risk of dangerous ICP elevations.