RESPIRATORY FUNCTION IN THE ELDERLY

Respiratory complications after surgery account for approximately 40% of the perioperative deaths in patients over 65 years of age.16, 47, 61 Although pulmonary dysfunction is more frequent in elderly patients after anesthesia and surgery, age itself is considered to be only a minor risk factor for perioperative pulmonary dysfunction until the ages of natural death are reached.29, 46 Nonetheless, with advancing age a significant decrement in the functional capacity of the respiratory system occurs.72 Longitudinal data show that even in older athletes, physiologic respiratory capacities progressively deteriorate with age despite continued vigorous endurance exercise (approximately 10% per decade).44, 54 Accordingly, the ability to deliver more oxygen to tissues than they require (“reserve capacity”) decreases by a factor of four from the age of 20 to the age of 70 years in apparently healthy individuals.26, 64 Inadequacy of respiratory function becomes particularly relevant in the supine position during anesthesia, as well as postoperatively.13, 14, 24 A variety of coexisting factors, prevalent in the elderly surgical patient, further predispose to pulmonary complications. These factors include smoking, obesity, and pre-existing pulmonary pathology. Chronic obstructive pulmonary disease (COPD—chronic bronchitis and emphysema), principally a geriatric disorder, is considered to be one of the major risk factors for post-coronary artery bypass graft (CABG) morbidity and mortality.29 Prolonged operations (longer than 6 hours) and thoracic or upper abdominal surgery significantly increase the risk for perioperative respiratory complications. Nonetheless, the number of elderly patients with pulmonary disease undergoing surgery, including high-risk procedures, is rapidly growing.40, 76 A better understanding of the altered physiology in the aged respiratory system may help to improve patient care and outcome. The purpose of this article is to sketch a panorama of the major age-related changes in the respiratory system. The following topics are addressed and their anesthetic implications discussed: structural alterations in the upper and lower airways; changes in respiratory mechanics and lung volumes; impaired efficiency of gas exchange; and alterations in ventilatory drive and control.