Respiratory issues are a common comorbidity associated with obesity. Given the high percentage of people with obesity, it is estimated that up to six percent have some form of Obesity Hypoventilation Syndrome (OHS). OHS results from a combination of obesity, daytime hypercapnia and sleep disordered breathing in the absence of any other disorder that may cause hypoventilation.
As weight increases, lung volume decreases, restricting air entry and lowering total lung capacity. People with chest or abdominal obesity are more likely to experience respiratory symptoms and decreased lung function, likely because fat in those areas lessens movement of the diaphragm during inspiration. This causes the diaphragm and other respiratory muscles to overwork and deteriorate.
Diagnosis is often delayed, occurring only when the patient has an acute, chronic respiratory failure, most typically when they reach their fifties or sixties. In many of these cases, patients are misdiagnosed with obstructive lung disease, such as chronic obstructive pulmonary disease, even in the absence of pulmonary obstruction. Arterial blood gas measurement is necessary to measure oxygen and carbon dioxide levels to accurately determine hypoventilation. Early diagnosis is important because OHS is also associated with hypertension, metabolic and cardiovascular diseases and elevated mortality.
Treatment of OHS must consider both aspects of the condition: respiratory support and the underlying issue of obesity. Continuous positive-airway pressure (CPAP) or bilevel PAP (BPAP) is used to treat the breathing disorder, particularly during sleep. However, this alone is insufficient. Weight loss is the first and preferred treatment for OHS and – in some cases – weight loss alone can improve pulmonary function. This can be challenging for patients with severe obesity that need to lose a significant amount of weight and, in extreme cases, bariatric surgery is recommended. Weight loss using a Very Low Calorie Diet (VLCD) can help patients with OHS reach their weight loss goals and also help reduce weight prior to surgery in order to decrease surgical and post-surgical risks.
Incorporating aerobic activity is also an important addition to lifestyle change. Patients who are exercise avoidant should be made aware that the strain the may initially feel when they begin a new activity is due to the effort of the heart and lungs supplying oxygen to muscles to strengthen them and reduce the effects of OHS. As their level of activity increases and the body more efficiently distributes oxygen to the bloodstream they won’t be as short of breath. Simple breathing exercises can also strengthen respiratory muscles to make their lungs more efficient.