Hypoventilation is a medical term expressing an insufficient exchange of gases. This leads to increased levels of carbon dioxide in the blood, and is especially dangerous when present in those with sleep apnea. A person will naturally adjust to the hypoventilation while awake, taking deeper and/or longer breaths as needed. During episodes of apnea though, where the body forcibly slows or shuts down breathing entirely in spurts, this can lead to dangerously high levels of carbon dioxide in the blood, and could lead to death in the most serious cases.
Hypoventilation can be caused by numerous factors. These may be caused by natural obstructions in the airway, or resistances to sufficient airflow. These are commonly brought on by other medical conditions that result in lower airway obstruction, including emphysema, cystic fibrosis and bronchitis. In other cases, the hypoventilation may be caused by another disease, or physical defect in the chest resulting in an abnormally shaped chest wall. People with muscular dystrophy run a higher risk of getting this disorder. People with diseases of the lung tissue are also at a high risk of developing this disorder. These are commonly caused by smoking, and smoking in general runs a high risk of development of a multitude of lower airway obstructing diseases. Any disease that inflames the lungs, and physically reduces the airflow passageway can also lead to this disorder. Sleep apnea may also cause this problem, though not through any physical means. The severely decreased intake of oxygen during some instances of sleep apnea can lead to the build up of carbon dioxide. Airway obstruction could also be the cause of environmental damage to the lungs, including exposure to, or breathing in of chemicals, pollution or other environmental factors.
Is some rare cases, the causes of hypoventilation may be unknown, as lungs and airways will appear normal under observation. This is termed as primary alveolar hypoventilation. A serious form of hypoventilation in infants called congenital central hypoventilation syndrome is thought to be the cause of some of the cases of sudden infant death syndrome or crib death, in which seemingly healthy infants unexpectedly pass away.
Common symptoms of hypoventilation will include headaches, heart problems, stomach problems and faintness. It may also lead to poor sleep due to common awakenings, and daytime sleepiness as a result.
Successful diagnosis of this disorder will include taking an arterial blood gas test to measure the levels of carbon dioxide in your blood. You may also be asked to take an overnight sleep study to ensure that no sleep disorders are present that could lead to nocturnal hypoventilation, a dangerous condition that can be fatal if one or both of the offending conditions are not treated.
Reduction or narrowing of the airway can be caused by an over-consumption of alcohol, benzodiazepines and barbiturates, and the use of respiratory stimulants is the most common method for counteracting this reduction.
When a sleeping disorder such as sleep apnea is present in any case involving hypoventilation, CPAP or BPAP treatment will be often be used. These devices contain small masks which are placed over the mouth and nose during sleep, and continually feed a steady dose of oxygen into the lungs to ensure a proper level of oxygen and carbon dioxide. The level this will be set at will be determined after taking the above tests.
In extreme cases of severe hypoventilation, these treatments must be delivered day long, and not just while sleeping.
Reviewed September, 2007