Causes of Obesity Hypoventilation Syndrome

Obesity-hypoventilation syndrome consists of significant breathing problems in obese people, but what causes it? By better understanding why it happens, you may be able to seek the right treatments that can set things right. It is also important to appreciate its association with obstructive sleep apnea, a common condition with overlapping symptoms. Learn about the important relationship between obesity, obstructive sleep apnea, and carbon dioxide retention during sleep.

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How Obesity Hypoventilation Syndrome Occurs?

Obesity-hypoventilation syndrome (OHS) occurs when breathing is insufficient to rid the body of carbon dioxide in someone who is obese. There could be a handful of underlying reasons that contribute to this result. In the end, the result is the same, and these breathing problems can lead to complete respiratory failure. This can be determined by measuring the levels of carbon dioxide in the blood, which are increased during wakefulness in people with obesity hypoventilation syndrome.

Carbon dioxide is a waste product that is normally blown out of our lungs in exchange for oxygen. When breathing becomes insufficient for various reasons, this cannot happen. Instead, the carbon dioxide stays in our circulation and builds up slowly. It becomes a poison with toxic effects, leading to drowsiness and (eventually) unconsciousness or even death.

The term hypoventilation refers to insufficient breathing. This can occur when the breaths are not of sufficient volume or when they are not frequent enough. Imagine that you can only fill your lungs half full. These shallow breaths would make it difficult to remove the carbon dioxide and take in the oxygen you need to live. In addition, if you breathe less often than you need to, you will quickly feel short of breath. The hypoventilation that characterizes this condition may be due to a combination of these factors. Unfortunately, those who are affected find that these limitations are beyond their conscious control to overcome.

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The important role of obstructive sleep apnea

It cannot be emphasized enough how central a role obstructive sleep apnea plays in this condition. In fact, sleep apnea occurs in 85 to 92% of people with obesity hypoventilation syndrome. This overlap may be due to a similar underlying mechanism and predisposing anatomy. It is also possible that OHS represents an extreme form of sleep apnea in which breathing is so impaired that it begins to have other daytime effects, most notably shortness of breath (or shortness of breath) with exertion.

As a reminder, sleep apnea occurs when the upper airways are partially or completely blocked during sleep. This obstruction leads to audible pauses in breathing. This disturbance has two consequences: the oxygen level falls while the carbon dioxide level rises. If these cases of apnea are infrequent, your body can recover and there may be no noticeable consequences. However, when apnea becomes more common, there is no time to set things straight. The processes that would normally compensate, including changes to correct the chemical balance of your blood, cannot take place.

Breathing becomes more difficult with obesity

In general, the effort to breathe becomes more difficult in obese people. It is difficult to expand the lungs against the extra pressure that the excessive weight imposes. Imagine trying to inflate a balloon with a straw. It is hard work. Now put a heavy book on the balloon and try the same. It’s going to be a real chore. Likewise, the extra weight of an obese person makes it challenging for the lungs to fill.

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The lungs are normally filled using the diaphragm and the respiratory muscles along the rib cage. When these muscles pull, the lungs fill like a bellows. Obese people have a modest reduction in muscle strength. Not only do they fight the resistance described above, but the muscles used are not as strong as they should be.

These factors in combination lead to increased work of breathing. This will tire a person, so that eventually more shallow or less frequent breaths are taken. This results in the hypoventilation that is so characteristic of this syndrome.

Body adaptation exacerbates hypoventilation

As a result of the breathing difficulties, the body tries to adapt to the situation. Unfortunately, some of these changes actually make hypoventilation worse.

The brain begins to ignore the signals of low oxygen levels and high carbon dioxide in the blood. These signals would normally prompt the brain to prompt the body to breathe faster in an attempt to correct the abnormalities. When the condition becomes chronic, the alarm is ignored. Fortunately, treatment quickly corrects this built-in response system.

Obese people are also known to have abnormal levels of a hormone called leptin. However, it is not clear what role leptin may play in altering breathing patterns. The research into this has led to conflicting evidence up to this point.

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Finally, because the lungs are not fully inflated, the lower lobes can remain collapsed. This makes it difficult to aerate the blood circulating to these parts of the lungs. As a result, the problems with the exchange of oxygen and carbon dioxide are exacerbated.

The underlying causes of obesity hypoventilation syndrome are multifactorial. Ultimately, it occurs when there is an insufficient exchange of oxygen and carbon dioxide. This may be due in part to the physical limitations imposed on the lungs by obesity. There is also clearly a role for obstructive sleep apnea, as this disrupted nighttime breathing just makes things worse. Even the body’s natural adaptations begin to fail. Fortunately, there are effective treatment options available that can correct this situation, including positive airway pressure therapy.

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