Equipment viva — the intracranial-pressure monitor, the external ventricular drain and the ICP waveform

Stimulus

You are shown a schematic of an intracranial-pressure monitoring system. Two catheter options are depicted: an intraparenchymal transducer (a fibre-optic or piezoelectric sensor placed directly into the brain substance) and an external ventricular drain (a catheter placed into the lateral ventricle and connected to an external pressure transducer and a collection chamber). Beside it is a normal intracranial-pressure waveform with three peaks labelled P1, P2 and P3, and the drainage chamber is shown levelled to the external auditory meatus.