Sleep Apnoea Test

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Sleep Apnoea

Obstructive Sleep Apnoea Syndrome, OSAS:

Snoring may also be associated with obstructive sleep apnoea. In this serious condition, your throat tissues obstruct your airway, preventing you from breathing.

Sleep apnoea is often characterized by loud snoring followed by periods of silence that can last 10 seconds or more. Sometimes, complete obstruction does not occur, but rather, while still snoring, the airway becomes so small that the airflow is inadequate for your needs. Eventually, the lack of oxygen and an increase in carbon dioxide signal you to wake up, forcing your airway open with a loud snort or gasping sound. This pattern may be repeated many times during the night.

Any space occupying lesion from nose orifice to vocal cords can predispose to obstructive sleep apnoea.

Clinical features and complications associated with the snoring and OSAS essentially result from the two main effects of the obstructive episodes.

1. Oxygen desaturation

2.The generation of high negative intrathoracic pressures.

Arousals: Recent studies suggest that the main factor producing arousal is the high level of negative intrathoracic pressure generated by increased respiratory effort associated with the airway obstruction. When the degree of respiratory effort reaches a certain threshold, arousal occurs, resulting in a return of tone to the upper respiratory muscles and the obstruction clears.

The patient is often unaware of these arousals which can occur many hundreds of times throughout the night. The effect of repeated arousals is a very disturbed sleep pattern which is reflected in the excessive day time sleepiness.

In OSAS, the bed partner will describe periods of very loud snoring interspersed with periods of silence during episodes. These episodes usually last 20-60 seconds but can last up to a couple of minutes, though most partners will not usually wait this long and will rouse the patient. The snoring then resumes before next episode begins.

The minimum criteria for diagnosis of OSAS are more than 5 episodes per hour.