When measuring intracompartmental tissue pressures to diagnose acute compartment syndrome, which of the following ‘delta P’ values is generally considered an absolute indication for emergency fasciotomy?

Explanation:
The 'delta P' (ΔP) is calculated by subtracting the intracompartmental pressure from the diastolic blood pressure (Diastolic BP - Compartment Pressure). A ΔP of less than 30 mmHg indicates inadequate capillary perfusion to the muscle and is considered an absolute indication for emergency fasciotomy to prevent irreversible muscle necrosis and Volkmann ischemic contracture. Reference: Campbell's Operative Orthopaedics, 14th Edition.