Chapter 9: Ventilatory Assistance

The respiratory system accomplishes gas exchange through four sequential processes: ventilation moving air into the alveoli, diffusion across pulmonary capillaries, perfusion delivering oxygenated blood throughout the body, and cellular diffusion providing oxygen to tissues. Breathing is regulated by the medulla and pons, primarily in response to elevated carbon dioxide, though patients with chronic obstructive pulmonary disease may depend on hypoxemia as their breathing stimulus. Understanding respiratory mechanics is essential for nursing practice; work of breathing describes the muscular effort needed to maintain ventilation, while compliance reflects lung stretchability with decreased compliance occurring in conditions like acute respiratory distress syndrome and increased compliance seen in emphysema. Resistance to airflow increases with airway narrowing from bronchospasm or secretions. Comprehensive respiratory assessment combines health history and physical examination, including evaluation of chest wall symmetry, accessory muscle use, abnormal breathing patterns such as Cheyne-Stokes respiration and Kussmaul breathing, and lung auscultation to identify normal versus abnormal sounds including crackles, wheezes, and stridor. Arterial blood gas analysis provides critical information about oxygenation, ventilation, and acid-base balance, with normal values for pH, carbon dioxide pressure, bicarbonate, and oxygen pressure guiding clinical decisions. Oxygen delivery occurs through low-flow systems where inspired oxygen concentration varies with patient breathing or high-flow systems providing precise oxygen concentrations. Mechanical ventilation becomes necessary during acute respiratory failure and can operate in volume-controlled, pressure-controlled, or spontaneous modes, each with distinct advantages. Positive end-expiratory pressure maintains alveolar recruitment to improve oxygenation. Nursing care incorporates the ventilator bundle approach emphasizing head of bed elevation, sedation management, ulcer and thromboembolism prevention, and oral hygiene to reduce ventilator-associated complications. Weaning from mechanical ventilation begins when the underlying respiratory failure improves, with spontaneous breathing trials serving as the gold standard for determining extubation readiness using parameters such as rapid shallow breathing index and inspiratory pressure measurements.