Basics of gas exchange
The ultimate goal of pulmonary gas exchange is adequate tissue oxygen (O2) delivery and carbon dioxide (CO2) elimination. This exchange of gas is a multistep process that begins with ventilation and movement of gas from the atmosphere through the various generations of airways into the alveoli of the lungs. Oxygen quickly diffuses across the alveolar-capillary membrane into red blood cells (RBCs), allowing for transport of O2to the tissues. The final step in gas exchange occurs in the tissues as oxygen diffuses into cells to meet the metabolic demands of the body. Similarly, CO2diffuses from the cells into RBCs at the tissue level and is transported to the alveolar capillaries to be exhaled into the atmosphere. Given the multiple steps involved in gas exchange for both O2and CO2, there are a number of points in which this process may become disrupted. Despite the complexity of this process, pulmonary gas exchange is generally remarkably effective. This process usually leads to the adequate elimination of CO2and to the delivery of O2to tissues and organs well in excess of the body’s metabolic demands.
