CPAP machine and sleep study accuracy when measuring AHI

[Lulabelle]

Hello.
I was diagnosed with moderate OSA after a sleep study in which I scored 16.2 AHI with a high Epworth score. I was put on CPAP which I found intolerable but persisted with in order to be considered compliant with regards to the DVLA and driving.

After 3 months on CPAP my AHI level was averaging at 8, and in subsequent months it lowered further and fluctuated between 3 and 10.

In the meantime I had lost a significant amount of weight (15% of my body weight) and was well within the normal BMI range so I persuaded the hospital to conduct another sleep study. I had a 5 day run-up (washout) not using the CPAP machine before the study, as instructed by the consultant. The results of this test were an AHI of just 4.2 so I have been discharged by the clinic and am now deemed not to have OSA so no longer use the CPAP.

My question is: if when using the CPAP machine I was registering up to 10, how could I register below 5 without the machine??
In other words, how accurate are these sleep tests and also how accurate are the CPAP machines? It is worth noting that I struggled so much with the CPAP that I spent many hours in the night just lying in bed very self-consciously breathing with the mask on. Also I found the whole thing so very distressing and uncomfortable that I spent quite a bit of time sobbing. Perhaps this skewed the results?

Many thanks.

[Kelly @ Intus]

Good Morning,

Thank you for your post.

Our clinicians advise that if you wish to retest for sleep apnoea and are currently using a CPAP machine or a mandibular advancement device (MAD), you should stop using the treatment for 5 days before completing a sleep study. This helps ensure the test accurately reflects your untreated sleep breathing patterns.

Hospital-based sleep studies are highly accurate, and CPAP machines are also very reliable at detecting and recording sleep apnoea events. Significant weight loss can have a substantial impact on sleep apnoea severity by reducing upper airway collapse during sleep. For some individuals, this improvement is enough to reduce their Apnoea-Hypopnoea Index (AHI) to a normal or near-normal level.

Given your previous diagnosis of moderate obstructive sleep apnoea (AHI 16.2), it is entirely plausible that your condition has improved significantly following your weight loss.

We are sorry to hear that your experience with CPAP therapy was not a positive one. However, the outcome you have achieved through your weight loss is a significant accomplishment, and you should be very pleased with the positive impact it appears to have had on your health.

Kelly