The Respiratory System

The pulmonary system is crucial for survival. Managing respiratory mechanics and airway requires a sophisticated understanding of pulmonary physiology. This chapter discusses the ways in which oxygen is brought into the body and carbon dioxide is expelled and reviews the principles of respiratory mechanics, including lung compliance, airway resistance, chemoreceptor and mechanoreceptor control of ventilation, hypoxic pulmonary vasoconstriction, distribution of perfusion, and other properties that affect oxygen and carbon dioxide transport. The respiratory system exists in a state of equilibrium, where the inward elastic recoil of the lungs is balanced with the outward elastic recoil of the chest wall. Airway resistance and compliance are important factors that affect ventilation and air movement. This chapter reviews the role that chemoreceptors and mechanoreceptors have on controlling ventilation, as well as the effects that hypercarbia and hypoxemia have on pulmonary and cerebral circulation, and the Bohr and Haldane effects that elucidate understanding of the hemoglobin dissociation curve. These principles all inform the care of patients who require mechanical ventilation, as we endeavor to support them through their surgery or intensive care stay. This review contains 7 figures and 38 references. Key Words: apneic oxygenation, Bohr effect, chemoreceptors, compliance, Haldane effect, hypoxic pulmonary vasoconstriction, resistance, respiratory mechanics, ventilation-perfusion