Basic principles of mechanical ventilation
Positive-pressure mechanical ventilatory support is a critical component in the management of patients with respiratory failure. However, it is important to note that this technology is supportive, not therapeutic, and it cannot cure lung injury. Indeed, the best we can hope for is to buy time by supporting gas exchange without harming the lungs. Positive-pressure mechanical ventilation is designed to provide substantial levels of respiratory support. The major goals are to unload the ventilatory muscles and optimize ventilation-perfusion matching to ensure adequate gas exchange. Important complications include ventilator-induced lung injury, cardiac compromise, oxygen toxicity, and patient discomfort. Applying ventilatory support often requires trade-offs as clinicians attempt to balance gas exchange needs with the risk of these complications. Future innovations cannot focus simply on physiologic endpoints. Rather, innovations should demonstrate benefits in clinically relevant factors, such as mortality, ventilator-free days, barotrauma, and costs. Only then can we properly assess the often bewildering array of new approaches to this vital life-support technology.
