135 - Mechanical Ventilation

Abstract

Mechanical ventilation is the process of using a device to support the delivery of gas to the lungs by replacing or augmenting the function of the respiratory muscles. Given that the mechanical ventilator is intended to augment or replace the respiratory muscle pump, effective mechanical ventilation must interact properly with the patient’s own respiratory efforts. The goal of mechanical ventilation is to maintain adequate levels of Po2 and Pco2 in arterial blood while also unloading the inspiratory muscles. However, when the mechanical stress applied to the lung is excessive, ventilator-induced lung injury may result. Mechanical ventilation can also cause ventilator-induced diaphragm dysfunction through a variety of mechanisms (ventilator “myotrauma”). Therefore, support with mechanical ventilation involves tradeoffs, balancing the need for providing adequate support while minimizing the risk of ventilator-induced lung injury, ventilator-induced diaphragm dysfunction, and other complications. Specifically, the need for potentially injurious levels of mechanical ventilation must be weighed against the benefits of supporting gas exchange. Finally, as respiratory failure stabilizes and begins to reverse, clinical attention shifts to ventilator withdrawal. Attempts to facilitate liberation from mechanical ventilation, however, must be balanced against the risk of premature withdrawal with consequent loss of airway patency, aspiration, and inspiratory muscle fatigue.