Obstructive sleep apnea (OSA) is characterized by repeated complete or partial collapse of the pharyngeal airway during sleep, causing cessation of airflow (apnea) or shallow breathing (hypopnea). Persons with OSA may have repeated arousals from sleep (to reestablish breathing) with each episode of apnea or hypopnea. The resulting sleep disruption often leads to daytime somnolence and compromised neurocognitive function.
This pattern of sleep arousal, coupled with intermittent hypoxemia, is associated with serious adverse cardiovascular outcomes, including stroke. Among surgical patients, OSA is associated with postoperative complications and the need for increased medical intervention. This review discusses why OSA is important in the perioperative setting, preoperative screening for OSA risk, and perioperative management of patients with likely or confirmed OSA.
OSA AT A GLANCE
Prevalence in the general population
Four percent of middle-aged men and 2% of middle-aged women meet minimal diagnostic criteria for OSA, according to a landmark cohort study from the 1990s. 1 This makes OSA more common than asthma among adults. Risk increases with age, as 24% of persons older than 65 years have OSA and up to 50% of nursing home residents have clinically significant OSA. 2
Prevalence in the surgical population
The prevalence of OSA in the surgical population is higher than that in the general population, and it can vary widely according to the underlying medical condition. A study of 433 patients undergoing general surgery reported a 3.2% prevalence of OSA, 3 but this study excluded patients undergoing cardiac surgery, in whom the risk of OSA is higher. In contrast, the prevalence of OSA among obese bariatric surgery patients has been reported at greater than 70%. 4 Notably, the patients in the general surgery study 3 who appeared to be at risk for OSA based on screening questions were invited to participate in a sleep study, whereas all patients in the bariatric surgery study 4 were evaluated through sleep studies. It is likely that the prevalence of OSA among the general surgery study patients would have been higher if all patients had been evaluated with polysomnography.
OSA can occur when any part of the upper airway does not function normally. Upper airway patency is determined by muscle activity, craniofacial and soft tissue structure, and sleep state. During sleep, upper airway muscles are relaxed, which reduces airway patency. Sleep is associated with pharyngeal narrowing and substantially increased inspiratory resistance even among persons without sleep apnea. A person who is awake can compensate for abnormal pharyngeal function through increased muscle activity. During sleep this muscle compensation fails, resulting in partial collapse and subsequent snoring, and sometimes prolonged obstructive hypoventilation. Complete closure results in apnea.
WHY OSA MATTERS
Health consequences of OSA
OSA is associated with serious health consequences, such as increased risk of motor vehicle accidents, stroke, and a number of cardiovascular conditions—hypertension, coronary artery disease, and atrial fibrillation.
Accidents. The daytime hypersomnolence resulting from OSA contributes to reduced vigilance and is likely responsible for an increased incidence of motor vehicle accidents. One study found that among a sample of men and women with unrecognized OSA undergoing polysomnography studies, the likelihood of motor vehicle accidents during the prior 5 years was significantly correlated with the subjects’ apnea-hypopnea index (AHI) score, which reflects the number of apnea or hypopnea episodes per hour of sleep. 5 Other studies have demonstrated similar associations.