Essential Anatomy and Physiology of the Respiratory System and the Pulmonary Circulation

Abstract

Knowledge of the clinical anatomy and function of the respiratory system is essential for the safe, efficient, and appropriate perioperative management of intubation, mechanical ventilation, and anesthesia for the thoracic surgical patient. The lung has ten (third-generation airway) bronchopulmonary segments on the right and eight segments on the left that are readily identifiable by fiberoptic bronchoscopy (two segmental bronchi on the left are considered “fused”). The anesthetic employed, both general and regional, will impact the control of respiration, reactivity of the airways, and the patient’s ability to maintain their airway, take a deep breath, and cough. Dynamic influences of ventilatory pattern, posture, body habitus, agitation or pain, and inflammation can cause “air trapping” and drastically reduce alveolar ventilation. The compliance and resistance of the respiratory system will change during the course of surgery, especially those procedures requiring one-lung ventilation, and may necessitate frequent adjustments of the ventilator to optimize gas exchange and reduce lung injury. Many drugs employed during cardiothoracic surgery will impact the lung’s intrinsic mechanisms to match ventilation to perfusion matching either directly on hypoxic pulmonary vasoconstriction (HPV) or indirectly by altering cardiac output or vascular resistance.