Chapter 31: Disorders of Ventilation and Gas Exchange

Clinical assessment of oxygenation relies on arterial blood gas analysis to measure partial pressure of oxygen and noninvasive pulse oximetry using spectrophotometric principles. Physical manifestations of respiratory distress include diaphoresis, pursed-lip breathing, and activation of accessory muscles during inspiration. Disorders affecting lung inflation encompass atelectasis, which involves collapse of alveolar tissue due to airway obstruction or external compression such as pleural effusion, and tension pneumothorax, a life-threatening emergency where intrapleural pressure exceeds atmospheric pressure, causing mediastinal shift and compression of the vena cava that critically reduces cardiac output. Obstructive airway disorders include chronic obstructive pulmonary disease with emphysematous changes where patients experience air trapping and hyperinflation producing characteristic barrel chest appearance. Asthma represents another major obstructive disorder classified by severity according to established clinical guidelines ranging from intermittent to severe persistent presentations. Pulmonary vascular disorders include pulmonary embolism, typically originating from deep vein thrombosis sources, which creates severe ventilation-perfusion mismatch and is diagnosed through D-dimer testing and imaging modalities. Chronic elevation of pulmonary vascular resistance leads to pulmonary hypertension defined by mean pulmonary artery pressure exceeding twenty-five millimeters of mercury at rest, a condition that may progress to cor pulmonale involving right ventricular failure secondary to chronic lung disease. Pharmacological management of pulmonary hypertension includes supplemental oxygen therapy and vasodilatory agents that reduce pulmonary vascular resistance and right heart strain.