Sleep is one of our most basic needs. It is necessary for survival and effective functioning. Lack of sleep can cause a host of problems - big and small.
Lack of sleep, or "sleep debt," can occur due to a variety of causes, of which sleep apnoea - or, temporary cessation of breathing in sleep — is an important part. Apart from reducing efficiency and concentration during the day, sleep apnoea can cause serious diseases like high blood pressure [hypertension], heart disease, stroke, and diabetes.
Sleep apnoea is defined as a 10-second cessation of airflow. Hypopnoea is described as a 10-second decrease in airflow.
AHI [Apnoea-Hypopnoea Index] is defined as the number of apnoeas plus the number of hypopnoeas divided by the number of hours of sleep. The following are the figures for AHI used for grading the severity of the disorder/s:
- Normal: 0-5
- Mild: 5-15
- Moderate: 15-30
- Severe more than 30.
Sleep apnoea can affect children and adults alike. It is characterised by periods of stoppage of breathing [apnoea] and periods of shallow breathing [hypopnoea].
There are many types of sleep apnoea:
- Central apnoea is complete cessation of airway and diaphragmatic movement
- Obstructive apnoea occurs when there is continued diaphragmatic movement without upper airway flow, as seen in people with enlargement of tonsils, adenoids, abnormalities of the face, and severe obesity
- Obstructive sleep apnoea occurs on and off during sleep due to obstruction
- Complex sleep apnoea, which does not fall into any of the above categories, does not respond to standard treatment.
The most common form of sleep apnoea, called obstructive sleep apnoea [OSA], is caused by partial, or complete, collapse of the upper airway.
In people suffering from obstructive apnoea, there is repetitive upper airway collapse during sleep. This condition affects four per cent of males and two per cent of females. The reason why airway collapse occurs in some, and not in others, is due to differences in airway anatomy - e.g., narrow passage, extended length of the pharynx [throat], and poor control of upper airway muscles that are responsible for keeping the airways open [dilators].
During wakefulness, our airways remain open, due to the high activity of upper airway muscles. However, when we sleep, this activity is reduced, or lost. It may also result in partial, or complete upper airway collapse. Other unknown reasons may also contribute to collapse.
During airway obstruction, there is no breathing taking place. The levels of oxygen in blood fall, and those of carbon dioxide rise. The body tries to compensate this change by increasing the force of breathing, but this doesn't work. Hence, such episodes often lead to arousal from sleep, following which we breathe heavily and rapidly, before falling asleep again. These cycles keep occurring throughout the night, resulting in disturbed and unsatisfactory sleep.
Factors that lead to sleep apnoea are:
- Age: elderly individuals
- Gender: male
- Smoking and tobacco usage
- Heavy alcohol consumption
- Narrow and long throat passages
- Abnormalities of the face, neck and jaw, tongue, an increase in the pads of fat around the pharynx, and easy collapsibility of the walls of the air passages.
- Ability to get aroused, surface tension in the airways etc.,
The effects of OSA vary in adults and children.
- Daytime sleepiness, decreased efficiency, and risk of accidents
- High blood pressure [hypertension]
- Increased glucose levels, decreased insulin sensitivity, and diabetes
- Metabolic syndromes
- Angina [chest pain], heart failure, stroke and heart rhythm abnormalities.
- Failure to thrive, or poor growth
- Increased load on the heart
- Increased daytime sleepiness and poor concentration
- Mental dullness, lethargy, irritability, aggressiveness
- Learning difficulties.
Symptoms may be divided into daytime and night-time symptoms. These include
- Morning headaches
- Impaired concentration
- Decreased libido
- Witnessed apnoeic spells
- Laboured breathing
- Increased urination
- Dryness of mouth.
The symptoms cited above are often the starting point for suspecting sleep apnoea.
Apart from a detailed clinical examination to effectively diagnose OSA, a test called polysomnogram, or sleep study, has to be done.
During this test, a person is monitored all through the night, as s/he sleeps in a hospital, or laboratory, and certain parameters are measured - most notable among them being oxygen saturation, electroencephalogram [EEG], the electrocardiogram [ECG], electrooculogram [EOG], chest movements, abdominal movements, the number of times s/he suffers apnoea, nasal oral pressure, temperature and limb movements.
The results of this study are useful to establish diagnosis and severity of OSA. New devices are also available to conduct tests at home. It is debatable whether they are as accurate as polysomnogram.
There are a number of treatments for obstructive sleep apnoea [OSA]. To begin with, simple measures like weight reduction, giving up smoking, avoiding supine sleeping position [lying down with the face up], sedatives and reducing sleep deficit due to other causes, are recommended. Dental appliances and surgical treatments aimed at relieving nasal obstruction and correcting defects of the tongue, jaw, uvula [flap of skin that dangles from the back of the throat], or bypassing the airways, are also useful in select cases. If the cause can be identified, it becomes easy to medically, or surgically, correct the problem. The mainstay of treatment for OSA is called Continuous Positive Airway Pressure [CPAP]. The CPAP device used is an air pump that delivers a specified flow of air into a mask that channels the airflow into the nasal cavity. This provides positive pressure and keeps the airway open while the person sleeps.
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