Hypopnœa

Hypopnea is a medical term for abnormally shallow breathing or slow respiratory rate. This differs from apnea in that there remains some flow of air.

Hypopnea comes from the Greek roots hypo- (meaning low, under, beneath, down, below normal) and pnoe (meaning breathing). Literally it means underbreathing.

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General information

In the diagnosis and treatment of sleep disorders, a hypopnea event is not considered to be clinically significant unless there is a 50% (or greater) reduction in flow and an associated 3% (or greater) desaturation in the person's O₂ levels for 10 seconds or longer, or if it results in arousal or fragmentation of sleep.

The direct consequence of hypopnea (as well as apnea) is that the CO₂ in the blood increases and the oxygen level in the patient’s blood decreases proportionate to the severity of the airway obstruction. This disruptive pattern of breathing generates disruptive sleep patterns, the consequences of which being that those individuals exhibit increased fatigability, lethargy, decreased ability to concentrate, increased irritability, and morning headaches. Basically, those individuals are extremely tired due to their inability to get a good night’s sleep.

Hypopnoeas can be either central (i.e., as part of a waxing and waning in breathing effort) or obstructive in origin. During an obstructive hypopnoea, in comparison to an obstructive apnoea, the airway is only partially closed. However, this closure is still enough to cause a physiological effect (i.e., an oxygen desaturation and/or an increase in breathing effort terminating in arousal).

A hypopnea index (HI) can be calculated by dividing the number of hypopneas by the number of hours of sleep. The apnea-hypopnea index (AHI) is an index of severity that combines apneas and hypopneas. Combining them both gives an overall severity of sleep apnea including sleep disruptions and desaturations (a low level of oxygen in the blood). The apnea-hypopnea index, like the apnea index and hypopnea index, is calculated by dividing the number of apneas and hypopneas by the number of hours of sleep. Another index that is used to measure sleep apnea is the respiratory disturbance index (RDI). The respiratory disturbance index is similar to the apnea-hypopnea index, however, it also includes respiratory events that do not technically meet the definitions of apneas or hypopneas, but do disrupt sleep.

Causes

Among the causes of hypopnea there are:

• anatomical defects such as nasal septum deformation or congenital narrowness of nasal meati and the gullet,
• overweight and obesity,
• neuromuscular disease or any condition that entails weakened respiratory muscles
• use of sedatives (sleeping pills, etc.),
• alcohol abuse,
• smoking,
• aging,

and some others that are typical of snoring and sleep apnea.

Symptoms

The most common hypopnea symptom is excessive sleepiness, which results from constant sleep interruption. People with hypopnea often have loud, heavy snoring that is interrupted with choking sounds or loud snorts followed by periods of silence, because not enough air can flow into the lungs through the mouth and nose. The periods of silence can last 20 seconds or longer and can happen many times each hour, resulting in poor sleep and reduced levels of oxygen in the blood.

Other symptoms of hypopnea may include depression, forgetfulness, mood or behavior changes, trouble concentrating, loss of energy, nervousness, morning headaches. Not all people with hypopnea experience all of these symptoms and not everyone who has these symptoms has hypopnea.

Consequences

Hypopnea is a disorder that results in excessive daytime sleepiness and compromised quality of life, including traffic accidents, diminished productivity in the work place and emotional problems.

Cardiovascular consequences of hypopnea include myocardial infarction, stroke, psychiatric problems, impotence, cognitive dysfunction, hypertension, coronary heart disease, and memory loss.

Treatment

The most common treatment for hypopnea is continuous positive airway pressure (CPAP). CPAP is a treatment in which the patient wears a mask over the nose and/or mouth. An air blower forces air through the upper airway. The air pressure is adjusted so that it is just enough to avoid the upper airway tissues from collapsing during sleep but apnea episodes return when CPAP is stopped or it is used improperly. For people with neuromuscular disorders the most common treatment is the use of BIPAP or other non-invasive ventilation.

Mild hypopnea can often be treated by losing weight or by avoiding sleeping on one's back. Also quitting smoking, refusal from alcohol, sedatives and soporifics before sleep can be quite efficient. Certain physical exercises that strengthen gullet muscles also bring some results in hypopnea treatment.

Also there's an operative method, i.e. surgery. Upper airway surgery is site-specific. Depending on the cause of obstruction it focuses on the soft palate, the uvula, tonsils, adenoids or the tongue. There are also more complex surgeries that are performed with the adjustment of other bone structures - the mouth, nose and facial bones. Surgery is actually the last thing that doctors recommend to resort to in hypopnea treatment. But sometimes it is the only choice when other options don't work.

See also

• Sleep apnea
• Sleep disorder
• Snoring
• CPAP
• Bradypnea