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How to find the optimum pressure
on your constant-pressure CPAP machine


by SuperSleeper and the members of the Apnea Board Forum

This page summarizes methods used to find the best pressure on a constant-pressure CPAP machine. For instructions on how to enter the Clinician Setup Menu (to change pressure) on your specific CPAP machine, go to our CPAP Clinician Manual Page



Get A Sleep Study First

The safest way to find your "optimum" setting on a constant-pressure CPAP machine is via an overnight "sleep study" and "titration" in a sleep lab or clinic.   If you have the resources to utilize a sleep clinic, we strongly suggest you do so.  A sleep study is used to diagnose and determine the severity of your sleep apnea and a titration is used to determine the optimum CPAP pressure that will eliminate the majority of your sleep apnea events.   A sleep study also helps doctors diagnose other sleep-related issues.  We do not recommend that new CPAP users change their pressure until they have had their first sleep study and lived with the prescribed pressure settings for several weeks. 


Consult With Your Doctor

We recommend that you consult with your sleep doctor before making any changes to your sleep apnea therapy.


Consider Upgrading To An Auto-CPAP

If you're considering adjusting your own CPAP air pressure settings, the safer method is to upgrade from a constant-pressure CPAP machine to an auto-CPAP machine. Auto-CPAPs (sometimes referred to as "APAP") adjust pressure automatically according to your ongoing needs. You can read more about auto-adjusting CPAPs here. Some say this is really the best long-term option, since your pressure needs change day by day, hour by hour as you sleep - and differ depending upon what sleep stage you're in. Your pressure needs are also affected by what you eat and drink, your body weight, drugs you take, your sleeping environment, sleeping position, and whether you're sick. A one-time titration in a sleep lab cannot account for all these changes and is at best an "average" pressure that should work for you "most of the time". An auto-CPAP will adjust to your changing needs on an ongoing basis.


Adjust Your CPAP At Your Own Risk

For small adjustments, or for those who do not have health insurance or the financial resources to pay hundreds of dollars to a sleep center, we offer the following recommendations. Keep in mind that we are not medical professionals and this is not medical advice; it's simply what we've learned on our own, so use this information at your own risk.


What Type Of CPAP Do You Have?

If you don't want to go the auto-CPAP route, there are two main types of standard, constant-pressure CPAP machines. The methods used to adjust pressure is dependent upon which type you have. The first type is a non-data-recording machine; the second is a machine that has data-recording capability. You'll need to determine which machine type you have. Data-recording machines usually store patient data that is viewable on the machine itself or via a removable "smart card" or other removable memory device like an "SD memory card" that is readable using a personal computer along with an attached memory card reader. Data-recording machines will record several variables that will help you determine optimum pressure, but the most common measurement is your "Apnea/Hypopnea Index" or "AHI", where the goal is to get your AHI to 5.0 or lower. Non-data-recording machines offer no solid data to use as you adjust for optimum pressure.


Adjusting CPAPs That Are Not Fully Data-recording

Since your machine will not record your AHI levels, you must use the "how-do-I-feel" method. You do not have a solid, statistical number to use as you determine the best pressure, so keep in mind you'll be using very subjective criteria. This is why we stress you go very slowly and follow these suggestions:
  • Adjust your CPAP pressure in small, incremental changesWe recommend that you do not change your pressure more than 0.5 cm/H20 at any one time.  Changing pressures too much can decrease the effectiveness of your therapy and may lead to unintended and potentially dangerous health complications.

  • Give it time to work.  After you make a pressure change, don't make any additional changes for a week or two.

  • Keep a written log of how you feel each morning, afternoon and evening.  Note any pain, daytime sleepiness, changes in energy level or mental alertness.  Make sure you listen to your body.

  • Don't change other variables in your lifestyle which may influence your pressure needs. If you change what you eat and drink, where you sleep, your exercise level, what drugs you take or other non-pressure-related factors, you'll have no way of knowing whether your improved wakefulness and energy was caused by your lifestyle change or your CPAP pressure change.

At some point during your experimentation with pressure changes, you will note "diminishing returns" where you actually start feeling worse, not better.  At this point, you should adjust the pressure back to the last pressure setting that made you feel the best. This will be your optimum CPAP pressure for a constant-pressure machine with no data-recording capability. Monitor how you feel from this point forward and if your wakefulness or energy level changes, re-evaluate your pressure level again.


Adjusting CPAPs That Are Fully Data-recording

If your machine is able to record your AHI levels, it is this number that you will use primarily to determine the effectiveness of your CPAP pressure changes. Please read the recommendations and warnings for owners of non-data-recording machines above - the method on how to adjust the pressure given there applies to you also, but you have the added advantage of solid numerical AHI data to supplement the "how-do-I-feel" method.

It's generally best to get your AHI below 5.0, but some are able to get it below 3.0 or lower, which is even better.

The Apnea/Hypopnea Index (AHI) is the frequency of abnormal respiratory events per hour of sleep. These events are classified as Apneas or Hypopneas. Apnea is when breathing (airflow) stops for 10 seconds or more. Hypopnea is a partial blockage of airflow resulting in arousal and a possible drop in oxygen level. An AHI of 45 would indicate that the patient is experiencing complete or partial airflow blockage 45 times per hour.

The generally accepted ranges are:

AHI < 5 per hour  =  No Sleep Apnea

AHI 5 to < 15 per hour  =  Mild Sleep Apnea- (some say that 5-10 would be called "borderline OSA")

AHI 15 to < 30 per hour  =  Moderate Sleep Apnea

AHI > or = 30 per hour  =  Severe Sleep Apnea

Again, take it slowly, recording your nightly AHI levels after each pressure change, and don't make large, sudden changes as you attempt to decrease your AHI to the lowest level possible. The AHI will help give you a more precise way to judge the effectiveness of your adjustments.


Additional Information

If you have further questions, please join the Apnea Board Forum and post your question there - we'd love to hear from you!

For instructions on how to enter the Clinician Setup Menu (to change pressure) on your specific CPAP machine, go to our CPAP Clinician Manual Page, where you can obtain the Clinician Setup Manual for your machine.

Good luck and sleep well.


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