mechanical power mechanical power mechanical power is a medical term which is a measure of the amount of energy imparted to a patient by a mechanical ventilator. respiratory therapist examining a mechanically ventilated patient on an intensive care unit. the more time a patient spends exposed to the forces applied to them by a mechanical ventilator, the higher the risk of suffering a ventilator-associated lung injury. for the physics concept, see power (physics) § mechanical power. while in many cases mechanical ventilation is a life-saving or life-preserving intervention, it also has the potential to cause harm to the patient via ventilator-associated lung injury. a number of stresses may be induced by the ventilator on the patient's lung. these include barotrauma caused by pressure, volutrauma caused by distension of the lungs, rheotrauma caused by fast-flowing delivery of gases and atelectotrauma resulting from repeated collapse and re-opening of the lung. the purpose of mechanical power is to provide a quantity which can account for all of these stresses and therefore predict the amount of lung injury which is likely to be seen in the patient.