i. What is OSA?
A mean AHI in CPAP therapy is more realistic than using arbitrary compliance rates, which in fact hide insufficient reductions in AHI. OSA is associated with significant morbidity, such as excessive daytime sleepiness, social unacceptable snoring and impaired quality of life.
ii. OSA severity classification
The severity of OSA is expressed in the apnea hypopnea index (AHI). An AHI of 5-15 is mild OSA, 15-30 moderate OSA and >30 severe OSA12. When the AHI is smaller than 5, a patient is not considered to be suffering from OSA, but may be suffering from habitual snoring. Consequently in all treatment modalities the aim is reduce the AHI below 5. The point at which the AHI becomes harmful remains unclear13. Whether a patient is "cured" when the AHI falls below 5 is questionable.