Reading Time: 6 Minutes
What’s inside?
- What is a low AHI Score?
- What is a high mask-leak rate?
- What can I do when the 2 don’t play nicely?
If using a CPAP machine for OSA (obstructive sleep apnea), understanding how effectively the therapy is working could help you improve your overall sleep quality.
The main goal is to get your AHI (Apnea-Hypopnea Index) as low as possible, but that isn’t the only factor.
If you are using a CPAP machine your AHI has probably been tested as at least 15… in that you stop breathing on average at least 15 times each hour during sleep.
What Is A Low AHI Score?
Single figures is good.
I’ve heard claims that everyone has some form of sleep apnea… in that everyone stops breathing during sleep at some point. I can’t find evidence to back this up but it’s an interesting place to start from.
The basic gauge splits severity into 3 camps, mild, moderate and severe.
Mild: 5 to 14.9 events per hour
Moderate:15 to 29.9 events per hour
Severe: 30 or more events per hour
Less than 5 wouldn’t be considered a concern by most sleep specialists… so maybe that’s where the claim everyone has sleep apnea has some roots?
When I was diagnosed with sleep apnea my events were 46 per hour, which is classed as severe. However, the number of patients receiving scores of 60+ is considerable. With a score of 60, I would stop breathing on average once during every minute of sleep.
And then there’s the question of how long I stop breathing for.
For some it is a momentary second or so. For others it can become a real concern. The longest I’ve heard of was 223.8 seconds recorded by a 70-year-old lady during a sleep test. That is almost 4 minutes without air. Thankfully, that example lies at the far end of the chart.
Key Points About Low AHI Scores:
- Therapy Effectiveness: A low AHI score generally means our CPAP therapy is working well to prevent airway obstructions. This is a positive sign that our treatment is likely helping us breathe more normally during sleep.
- Improved Sleep Quality: Fewer apneas and hypopneas (partial airway collapse) usually lead to better sleep quality and less disruption during the night.
- Validation of Treatment: A low AHI score often validates the CPAP settings are effective for managing your sleep apnea.
But a low AHI score is only part of the story. While strapping a wind-tunnel to our face when we sleep can improve our chances of staying alive longer, it comes with the downside we weren’t designed to sleep like that.
As we move around at night, that life-extending mask kinda gets in the way… getting pushed around so much the perfect seal we had as we drifted-off is replaced with a mini-hurricane aimed at our ears and eyes.
And that wonderful slumber we worked so hard to achieve goes out of the window…
What Is a High Mask Leak Rate?
The mask leak rate refers to the amount of air escaping from the CPAP mask. Leaks can occur if the mask doesn’t fit properly or if there are issues with the mask’s seal. High mask leak rates can affect how well the CPAP machine delivers the necessary air pressure to keep our airway open. But… as we’ve seen… just lowering the AHI is only part of the story.
Key Points About High Mask Leak Rates:
- Impact on Pressure Delivery: High leak rates can result in some of the prescribed pressure escaping, which might affect the machine’s ability to maintain the right pressure levels needed to keep your airway open.
- What is a good leak rate?: It may seem strange but a perfect seal isn’t the goal. A leak rate of somewhere between 20 and 24 L/min (litres per minute) is considered pretty normal. Many masks are vented, in they are designed with little holes to allow a prescribed amount of air to leak in order to prevent the mask being blown off our face.
For unvented masks, the best way I’ve heard a good fit described by a sleep technician was for the mask to sit like a hovercraft on the face… with a controlled amount of air gently and quietly seeping through the tiny gap.
- Discomfort: Leaks can cause discomfort and disrupt your sleep, making it harder to tolerate CPAP therapy. Many of us are also guilty of over-tightening our masks with the aim of getting a better seal… so…
What can I do when the 2 don’t play nicely?
All is not lost though. We don’t need to compromise a low AHI score just to prevent mask leaks from waking us up and impacting what could possibly be an even lower AHI.
- Need for Adjustment: Over-tightening can cause just as many problems as having a loose mask… and sometimes more. While a loose mask creates air-leaks, an overly tight mask can also create leaking as it isn’t fitting to our face as intended. Also, the tighter the mask… the more likely we will have red mask-shaped marks around our nose and mouth in the morning. So, if experiencing high leak rates, it’s important to ensure that the mask is fitted correctly but not so tight it creates a new set of problems to deal with.
- Check the settings: Air-leaks could also be caused by the air pressure settings being too high. When I first started on CPAP around 4 years ago, I had real trouble getting used to it and felt like I was struggling to breathe. At the time, I spoke with my sleep clinic and they raised my maximum pressure from 12 to 20cmH2O (centimetres of water).
This did the job and I didn’t feel claustrophobic anymore. Fast forward all these years and I had forgotten all about this change until I got fed-up with my mask not sitting right and called the sleep clinic again. They dropped the max pressure back to 12 and suddenly my mask fitted better again. Strangely, due to having an autoset machine, my max pressure hadn’t reached 12 in the past week’s data they checked – but the mask fit still improved. If there’s any uncertainty about what our air pressure settings should be, the sleep clinic can conduct a titration test to help find those for us.
So, is a low AHI good?... Well, there aren’t many people around who would argue it isn’t. After all, it’s probably the reason we are strapping a mask to ourselves in the first place. However, it isn’t the only factor.
As we have seen, there are other aspects of sleep that can have a huge impact on our health too.
Being able to flow through the sleep cycles, including the all-important recovery phase of REM sleep and the body repairing deep sleep, are crucial for our overall well-being. So… while getting our AHI score down and actually breathing more is the first crucial step, keeping a stable sleep pattern is a good goal number 2.
Finding the right mask… or masks… is important – even switching between them depending on how we feel on that evening – is really important too. Keeping a good mask seal is likely to prevent us waking up before we naturally need to, resulting in our therapy have a better shot at actually helping us sleep better and – as a result – improve our overall health.
Whenever I ask our community what you would like to improve about your CPAP use, a better mask seal is usually in the top 2 replies. And I’ve been trying to figure out a solution to help too… unsuccessfully so far, I’m sorry to admit. Mask liners are out there but it only takes a quick look at reviews to see they unfortunately work for a only a small section of CPAP users. The search goes on. Maybe one day someone will crack that one.
For now, making the most of what is within our control seems like a worthy goal… and improving our mask seal using other tools – while keeping our AHI low – is within our grasp.
Cheers,
Alan
P.S. I have taken to creating various bits on sleep and sleep apnea. If you would enjoy hearing more and find out where else you can find stuff like this, you can get my weekly Triple Whammy email, which has 3 short topics each week. Some written or recorded by me and others I’ve found out there in the strange world we live in.
If this is you, sign up here and you will get the very next one.