Failure of pulse oximetry in the assessment of raised limb intracompartmental pressure.

Pulse oximetry has been proposed as an aid to monitoring raised intracompartmental pressures (ICPs). ICP and percentage haemoglobin oxygen saturation in the affected limb were studied in 10 consecutive patients with raised ICP. Compartment pressures ranged from 28 to 64 mmHg (mean 40.9 mmHg). In two patients with absent pulses, pulse oximetry failed to detect pulsatile flow and recorded 0 per cent saturation. The remaining eight patients, including four with absent peripheral pulses, all had percentage haemoglobin saturations within 2 per cent of the opposite normal limb. Arterial haemoglobin desaturation was not associated with raised ICP. The presence of an oximeter signal and a normal reading does not necessarily imply adequacy of tissue perfusion. Pulse oximetry does not appear to be a reliable aid in the diagnosis or monitoring of impaired perfusion due to raised ICP.