In obese patients, the body's oxygen consumption and carbon dioxide production are elevated, even during periods of rest. This results in an increased need for air exchange, higher breathing effort, reduced efficiency of the respiratory muscles, and decreased flexibility of the lungs.
- Obstructive Sleep Apnea (OSA): Characterized by intermittent cessation or reduction of breathing due to obstruction, often caused by excessive soft tissue and the collapse of the throat during sleep. OSA, which is frequently underdiagnosed, can lead to low blood oxygen levels, heart issues, irregular heartbeats, and even sudden death, risks that are significantly higher following surgery. This is because residual anesthetic and pain medications can weaken the body's response to low oxygen levels and high carbon dioxide levels, exacerbating airway obstruction and reducing lung ventilation.
- Chronic Hypoxemia: Leads to widespread blood vessel constriction, increased pressure in the lung's arteries, failure of the right side of the heart due to pulmonary hypertension, and increased red blood cell production as a compensatory mechanism.
- Obesity Hypoventilation Syndrome: This syndrome, characterized by a diminished response to carbon dioxide, results in decreased lung volumes, specifically functional residual capacity and expiratory reserve volume. This reduction contributes to the closing of small airways, mismatched air and blood flow in the lungs, and low oxygen levels, particularly when lying down.
- Pulmonary Hypertension: Obesity can induce low oxygen levels within the air sacs of the lungs, causing constriction of the blood vessels in the lungs.
- Asthma: The risk of asthma increases due to acid reflux and minor aspiration events, which trigger inflammation through increased stress on the airways. Remarkably, bariatric surgery improves or resolves asthma symptoms in most patients, with roughly half achieving full resolution in published series, by addressing the root causes, including obesity-induced inflammation and mechanical stress on the respiratory system.
