Alveolar mechanics: A new concept in respiratory monitoring

Abstract

A detailed understanding of respiratory mechanics during mechanical ventilation aids diagnostic accuracy and facilitates close monitoring of patient progress, allowing individualized ventilator adjustments aimed at minimizing ventilator induced lung injury. Respiratory mechanics can be described in terms of total respiratory, lung, and chest wall components and include compliance, resistance and are dependent on tidal volume, airway pressures, and flow for calculation. The interplay between the respiratory mechanics and ventilator delivered volume, flow, and pressure have an important role in the development of ventilator induced lung injury. The knowledge of alveolar dynamics and mechanics in the critically ill are lacking with much information originating mainly from bench and animal models of healthy and injured lungs. In this article we introduce the concept of alveolar compliance, resistance that depend on measuring the trans-alveolar pressure using esophageal balloon manometry and alveolar tidal volume using volumetric capnometry. This may have multiple implications in the understanding of components of ventilator induced lung injury specifically alveolar stress, strain, and mechanical power. Further studies are warranted to further understanding the monitoring and usefulness of alveolar mechanics. Keywords: Alveolar compliance and resistance, alveolar tidal volume, trans-alveolar pressure, alveolar stress and strain, alveolar mechanical power