Question
How does mechanical ventilation cause lung injury beyond issues of volume and pressure?
Answer
While volume, pressure, and inspiratory time are all critical factors in safe ventilator management, the most dangerous component of mechanical ventilation is the act of intubation itself. The placement of an endotracheal tube fundamentally alters lung physiology by introducing sustained positive pressure, increasing mean airway pressure, and setting the stage for potential ventilator-induced lung injury (VILI). Even with careful settings, the mechanical interface between patient and ventilator can disrupt natural gas distribution, leading to uneven inflation where healthy alveoli are overstretched and poorly compliant alveoli remain under-ventilated.
This imbalance not only risks structural injury to the alveoli, such as stress fractures in the capillary-alveolar membrane, but also triggers inflammatory responses, impairs surfactant function, and disrupts pulmonary blood flow. Both overinflation and underinflation can compromise ventilation-perfusion (V/Q) matching, with systemic consequences extending to cardiac output, organ perfusion, and overall patient stability. Neonates and infants are especially vulnerable due to their limited surfactant reserves.
Understanding that the harm begins with intubation underscores the importance of prevention and the careful use of non-invasive strategies whenever possible. When mechanical ventilation is necessary, strategies that minimize pressure, volume extremes, and uneven gas distribution are essential to protect lung integrity and reduce systemic complications.
This Ask the Expert is an edited excerpt from the course, MAP vs. NAP: The Impact of Mechanical Ventilation on Hemodynamics, presented by Evan Richards, Advanced Practice Clinical Consultant, BSc, RT.
