New PAINTS Episode: Change Management Methods: QI Methodologies and Framework

Normal aging is associated with a number of different changes in the respiratory system. These changes include alterations in control of breathing, pulmonary mechanics, blood flow, lung volumes, and lung architecture and place elderly patients at increased risk of postoperative pulmonary complications. Closing capacity and functional residual capacity are increased, although closing capacity increases more in comparison. When functional residual capacity falls below closing capacity, small airways collapse leading to increased shunting and decreased oxygenation. This increase in ventilation-perfusion mismatch is primarily responsible for the increased alveolar-arterial gradient seen with aging. There is a decreased resting arterial oxygen tension with impaired effect of pre-oxygenation in aging patients. Total lung volume remains relatively unchanged while residual volume increases and vital capacity decreases.

Changes in lung architecture include changes in collagen and elastin leading to impaired elastic recoil of the lung. Overall lung compliance is increased and alveolar surface area is reduced. There is an increase in the size of respiratory bronchioles and alveolar ducts with a tendency toward collapse of airways with exhalation and an increased risk of air trapping. Gas exchange is impaired with increased anatomic dead space and decreased diffusing capacity. Work of breathing is increased due to increased elastic recoil during inspiration and flattening of the diaphragm with the chest becoming more barrel-shaped. Decreases in activity of the central nervous system led to decreased ventilatory responses to hypoxia, hypercarbia, acidosis, and mechanical stress making patients at increased risk of hypoxia postoperatively. Hypoxic pulmonary vasoconstriction is also reduced in older patients.