Understanding Pathophysiological Concepts Leading to Obstructive Apnea

Obstructive sleep apnea (OSA) results from a combination of several factors leading to the obstruction of the upper respiratory tract (URT). OSA represents a systemic pathophysiological entity and leads to many comorbidities such as hypertension, coronary ischemia, and stroke. Patients with this pathophysiological entity experience also an increased risk of postoperative complications. Obesity is certainly the main cause of developing OSA. However, many other predisposing factors influence the genesis of obstructive apnea. It is important to understand the complexity of the interactions between predisposing factors to understand the relationship between weight loss following obesity surgery and the improvement in the severity of OSA. In this narrative review, we expose the seven major categories of predisposing factors that interact to generate obstructive apneas in patients, namely the anatomic abnormalities of the URT, the mechanical and the metabolic responses of the upper airway musculature, the loop gain, the arousal threshold, and the hormonal abnormalities. The genesis of apnea is the result of a complex dynamic interaction between the anatomical risk factors and the compensatory neuromuscular reflexes. All of these points are integrally part of the perioperative care of the obese patients. Finally, we will discuss different options for weight reduction.