Episode 340: Keywords Part 35: Respiratory Physiology

Respiratory physiology serves as a critical foundation for anesthesia practice, particularly regarding lung volumes, gas exchange, and ventilation-perfusion matching. Functional residual capacity (FRC) decreases during induction, supine positioning, and pregnancy, potentially falling below closing capacity and causing airway collapse. Dead space, categorized into anatomic and physiologic components, significantly impacts gas exchange efficiency, with the Bohr equation providing a quantitative measure of dead space fraction. Pulmonary vascular resistance follows a U-shaped curve, reaching its nadir at FRC, while hypoxic pulmonary vasoconstriction diverts blood flow to better-ventilated lung units. Oxygen transport relies heavily on hemoglobin binding, with the oxyhemoglobin dissociation curve illustrating the impact of pH, temperature, and 2,3-DPG on tissue unloading. Carbon monoxide poisoning presents a unique challenge, as it shifts the curve to the left and produces falsely normal pulse oximetry readings despite dangerously low oxygen content.