Diagnosis of Obstructive Sleep Apnea
Objective testing method is employed to make an initial diagnosis of some patients who complain of snoring and excessive day time sleepiness.
- Epworth sleepiness scale is used to gauge the extent of day time sleepiness with the help of a questionnaire answered by the patient.
- Nocturnal polysomnography is considered the best evaluation tool for diagnosing obstructive sleep apnea. This tool helps in assessing the patient in a sleep laboratory by applying several physiological parameters when the patient is asleep.
Apneic events can then be documented based on chest wall movement with no air flow and low oxygen levels in the blood (measured by oxy-hemoglobin desaturations).
A respiratory disturbance index (RDI) is then calculated and expressed as the number of abnormal respiratory events per hour of sleep. The cut-off point adopted by a few sleep laboratories, in the case of continuous positive airway pressure, is RDI of 20 episodes per hour.
A multiple sleep latency test (MSLT) measures the extent of daytime sleepiness. The time required by an average adult to fall asleep during the day is 10 minutes; therefore it is considered abnormal if the mean sleep latency is below 5 minutes.