Hypoventilation is a medical term that is frequently used to describe the inefficient and insufficient exchange of gasses. As we all know, we inhale air from which oxygen is taken in by the lungs and exhaled air is rich in carbon dioxide. If the exchange of gasses does not occur properly, the level of carbon dioxide in the blood increases.
For those with sleep apnea, hypoventilation becomes dangerous. When a person with hypoventilation is awake, he or she will make up for the insufficient gas exchange by breathing forcefully. It often happens almost involuntarily. However, in sleep apnea, the body shuts down breathing for short moments. In these cases, the lack of oxygen will wake the brain up, and it will forcefully breathe in.
This is why those with sleep apnea often experiences snoring or loud gasping during sleep. Those with sleep apnea also experiences daytime sleepiness. Sleep apnea, when paired with hypoventilation, may cause critical conditions and even death. A lot of people with sleep apnea will never even know that they have it. It is a chronic condition and most people who are diagnosed with it already had it for years before it was detected.
Causes of hypoventilation
Obstruction in airway-
Now, there are numerous factors that can cause hypoventilation. One very common cause has an obstruction in the airway. This can be a natural one, or due to some inflammation caused due to the effect of medicine. There may also be a physical defect, such as muscular dystrophy. An abnormally shaped chest wall may also be a physical reason behind hypoventilation.
Other common causes of hypoventilation include bad lifestyle habits, such as smoking. Smoking, in general, causes a lot of diseases that begin from obstructed airways in the respiratory system.
Lung tissue disease-
Other than these, some lung tissue diseases may also be a cause. External and environmental factors affecting lungs and lung tissues are also known to cause hypoventilation.
Sleep apnea is also known to cause this issue in the long term. As mentioned before, paired with severe sleep apnea, hypoventilation can be fatal. Sleep apnea does not cause hypoventilation by any physical means. During sleeping, the severe lack of oxygen may cause the build-up of carbon dioxide and therefore causing breathing troubles.
Types of Sleep Apnea and its link to Hypoventilation
Generally, sleep apnea is of two types, central sleep apnea, and obstructive sleep apnea.
Central Sleep Apnea-
In the case of central sleep apnea, the body does not make any effort to breathe. The brain, which controls the muscles allowing us to breathe, fails to send a signal to the muscles. Therefore, breathing stops. Moreover, the patient also does not make any efforts to breathe at all. Central sleep apnea is generally uncommon.
Obstructive Sleep Apnea-
The more common form of sleep apnea is obstructive sleep apnea. Obstructive sleep apnea occurs when certain muscles in your airway relax as you sleep, and thereby blocking the pathway. This causes breathing to start and stop repetitively during sleeping.
When untreated, sleep apnea can be very serious in nature. Sleep apnea is generally known to cause issues like diabetes, stroke, and high blood pressure and thereby, increase risks of heart attacks. Lack of oxygen causes arrhythmia or irregular heartbeats and is much more likely to increase the risk to a heart failure.
Heart failure from Sleep Hypoventilation
Hypoventilation is also classified into multiple types. These are central alveolar hypoventilation, obesity hypoventilation, and COPD or chronic obstructive pulmonary disease. People with Central alveolar hypoventilation suffers from sleep disturbances, but generally, this type remains undetected unless a respiratory failure occurs. Obesity hyperventilation is often linked with chronic right-sided heart failure. It is characterized by loud snoring, fatigue, nocturnal choking and headaches in the morning. Patients with hypoventilation and COPD usually are the worst case.
Heart failure from hypoventilation usually occurs when the oxygen levels in the blood go too low. Hypoventilation and oxygen saturation levels generally deteriorate during sleep. Due to metabolism, large quantities of volatile and non-volatile acids are generated in the body. Fats and carbohydrates metabolize to form carbonic acid. Generally, these are excreted via the lungs, and when that does not properly happen, acid accumulation occurs. Ventilation strictly is regulated by chemoreceptors such as PaCO2 and PaO2. This leads to hypercapnia and finally heart failure.