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CPAP Machine Settings: Pressure, Ramp, EPR, CFLEX, Auto-Start

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CPAP machines can make a world of difference in the quality of sleep you receive each night if you’re a sleep apnea patient. You’ll receive optimal benefits from your sleep apnea therapy when your CPAP machine settings are where you need them to be to keep your airways clear and unobstructed throughout the night.

These are some of the CPAP settings you’ll want to become familiar with as you explore your CPAP machine and learn more about how it works for you.

What Does My CPAP Pressure Setting Mean?

The CPAP pressure setting indicates the amount of pressure behind the air being sent through your mask at night. The pressure reading is typically abbreviated as “cm of H2O” or “cm of CWP.” The lowest setting on most CPAP machines is four or five CWP with maximum settings as high as 25 or 30 CWP (depending on the type of machine you have.

Most CPAP users require more than the minimal CPAP pressure settings and less than the maximum settings. While many people believe that the pressure settings are determined by the severity of the sleep apnea, that isn’t necessarily the case. In fact, there are numerous factors that determine which setting is the most appropriate for individual CPAP users.

Though it is true, to some degree, that people with severe OSA often do require higher settings to maintain unobstructed airways while sleeping, other contributing factors play roles in determining this, including:

  • Nasal obstructions
  • Obesity
  • Medications
  • Sleeping positions
  • Allergies

Others may even need to consider varied pressures throughout the night, particularly those who shift sleeping positions and at different sleep stages.

What Does My CPAP Ramp Setting Mean?

CPAP machines deliver a fixed amount of pressure into your airways at night. One of the challenges for many CPAP wearers is exhaling against the continuous pressure stream. Breathing against this powerful stream of air, especially for people who have higher than average prescribed pressure settings, can be discouraging and may even affect compliance.

Enter the CPAP ramp feature. Since the actual purpose of the CPAP machine is to deliver a stream of air while you sleep, the ramp feature, as its name implies, serves as a ramp that starts out delivering a lower amount of pressure allowing wearers the opportunity to fall asleep before the higher pressure settings engage.

The CPAP ramp is most commonly used to increase the air pressure incrementally, every five minutes, over a 45 minute period of time. There are devices that provide different ramp settings to meet the needs of different CPAP wearers. Work with your sleep technician to identify the best choice for you.

What Is EPR on CPAP?

Expiratory Pressure Relief (EPR) is a feature on some CPAP machines that reduces the amount of air pressure released by the device during exhalation. This setting makes it easier to exhale against the flow of air while using a CPAP machine.

How does EPR work? The three settings allow CPAP wearers to reduce the pressure by one, two, or three pressure points when exhaling. If you choose an EPR or three, for instance, and your normal pressure setting is 10, the machine will automatically reduce the pressure to seven when you’re exhaling then return it to 10 when you inhale.

The feature essentially makes it more comfortable for CPAP users to use their devices throughout the night, improving compliance which offers better outcomes for CPAP patients.

What is CFLEX?

C-FLEX is similar to EPR and is used by different CPAP machine makers. The goal of C-FLEX is the same as the goal of EPR – to make wearing CPAP masks more comfortable for patients with obstructive sleep apnea (OSA). C-FLEX accomplishes this by reducing air pressure sent into the airways prior to exhalation and restoring them to the prescribed settings just prior to inhalation.

This means patients do not need to work as hard to breathe against the machine while maintaining the appropriate supply or air pressure coming in while inhaling. The machine adapts to meet the changing air pressure needs of CPAP wearers on a person-by-person basis rather than offering a one-size-fits-all approach to adjusting the airflow.

  • A-FLEX. Moving beyond the abilities of C-FLEX on CPAP machines, AFLEX offers a more sophisticated analysis of breathing cycles and adjusts the pressure accordingly. This technology is only available on Auto CPAP devices, however.
  • Bi-FLEX. More closely mimics natural breathing patterns than C-FLEX making it feel more natural to CPAP wearers.
  • C-FLEX +. Only available on fixed pressure CPAP devices, this feature combines the intuitive adjustments of A-FLEX with the traditional C-FLEX therapy for a more comfortable transition from inhalation and exhalation pressures.

As you can see, CPAP makers that offer C-FLEX technology are constantly building on this technology to create even more natural feeling sleep experiences for CPAP wearers.

What Does Auto Start On My CPAP Do?

Auto-start is a feature that allows the CPAP machine to automatically begin delivering air pressure when the wearer puts on his or her CPAP mask. This allows wearers to get comfortable in bed before turning on their machines and eliminates some of the discomfort associated with maneuvering hoses and switches when trying to settle in.

Anyone who has ever had a wrestling match with their hoses, sheets, blankets, and pillows knows the struggling of forgetting to turn the machine on before settling in. Auto start eliminates that struggle.

What Does Mask Leak / Mask Fit Alert Mean?

Unfortunately, CPAP masks don’t always have a snug seal, resulting in mask leaks. For example, many CPAP machines, including some ResMed machines offer a “Leak Alert” which can be enabled or disabled, and many Respironics positive airway pressure machines also have “Mask Leak Alert” feature: “Mask Leak Alert”. Some of the ResMed machines also offer a “Mask Fitting Feature”.

These alerts notify CPAP wearers if there is an airflow leak in their mask reducing the air pressure that actually reaches wearers through the course of the night. The alert will not only improve CPAP outcomes but will also help improve compliance as people sometimes give up on CPAP therapy because they aren’t receiving the full benefits they are meant to offer.

The better you understand the various CPAP settings on your machine, the greater your ability to make choices that benefit your needs best. Working with your sleep technologist or CPAP machine and mask specialist can help you get even more mileage from your CPAP experience to make it more comfortable and productive for you.

Reach out to our CPAP expert by calling 1-800-356-5221 or using our live chat feature to learn more about optimal CPAP machine settings.

  • David Repasky

    David Repasky has been using CPAP treatment since 2017 and has first-hand experience with what it's like to live with Sleep Apnea. He brings the patient's perspective to the CPAP.com blog and has received formal training in CPAP machines, masks, and equipment.

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10 Responses

  1. There have been two occasions where I get a wheezing sound on respiration, not immediately, but after a few minutes of starting the machine. Might this be caused by the expiratory pressure relief (EPR) feature? I am sure it is not a mask leak.

    1. Hi John, my apologies for the delayed response. It is possible that the wheezing sound is due to the EPR. Try increasing the EPR to 3, if it isn’t already at this setting.

      For further questions, or concerns, please reach us at: 1-800-356-5221, or you may e-mail us at: cpap@cpap.com.

      Enjoy your day!

    2. I doubt you still need help, but I am almost certain the wheezing you hear is more of a “high-pitched whirring noise”. Essentially, its because the ball bearing inside the fan eventually wear down over time/extended use, and will gradually get worse over time.

      It happened to me after a few years or so with my first cpap machine. Luckily, I get mine ghrough the VA, and the tech that came out to look at it didnt even bother opening it up and put me down for a brand new one when she heard that I had it for two years and it was an outdated model anyways.

      These machines are only quiet for a month or so before you gotta move them further and further away from you. I cant stand the sound matching the rythym of my breathing when trying to fall asleep. Ive gotten pretty mad haha.

      I would invest in some comfortable tiny headphones for your phone, look up “Awesome fan noise” on YouTube and it will put you right to sleep. I cant even hear my four yr old get up in the morning. My wife hates it, but it works haha. Good luck.

    1. Hey Sam, if your pressure setting is too high, the therapy may be uncomfortable, you might receive significant air leaks from you mask, you may experience dry mouth and throat, even if you’re using a humidifier. Also, you may find yourself swallowing a lot of air, you might have an AHI, above the normal five events per hour as well, you may have feelings of tiredness, or fatigued during the day.

      If your pressure is too low, you may have an AHI which is above the normal 5, you will most likely still snore a lot, you may feel like you’re gasping for air, which in turn causes you to swallow air (Aerophagia).

      Basically, if your pressure setting is too high, or low, you would not receive the therapy you need.

      For further questions, or concerns, please feel free to reach us at: 1-800-356-5221, or you may e-mail us at: cpap@cpap.com.

      Have a great day!

  2. I have an Airsense 10 Auto, in the morning when I awake to use the restroom and come back to bed; the machine goes into this pulsing mode. It’s very light but very annoying as it prevents me from falling back asleep. Any ideas on how to fix this or if it’s some kind of update?

    1. Hi Nick,
      I’m sorry to hear that you’re having some problems with your machine. I can’t be certain as to what is causing the pulsing mode you’re experiencing.

      Do you have your Expiratory Pressure Relief (EPR), on? If so, You may try turning it off to see if the issue persists.

      Please see the link below to our cpaptalk.com blog to read what other CPAP users, are saying about the pulsing pressure.

      If the problem persists, please feel free to contact us at: 1-800-356-5221 for over the phone troubleshooting, otherwise, you may want to speak with whomever supplied you with your machine.

      We wish you the best!

  3. I just got Dreamstation auto cpap machine. Love it’s size and the heated tubing without having to always use water. However, I can hear myself breath in and out. It’s like I am listening to my husband snore and it keeps waking me up during the night. Any suggestions? I always use the ramp feature but it still happens. Help!!

    1. Hi Bonnie,
      I’m sorry about the troubles you’re having with your therapy. Please make certain your EPR is on and if so, try adjusting to see if this decreases the noise you’re hearing.

      If the problem persists, please give us a call at: 1-800-356-5221, for over the phone assistance.

      Best Wishes!

  4. On a normal situation after how long can one change the CPAP MACHINE
    If not what about the bits that come off or with the machine the likes of the tube musk etc
    And any advise on the cleaning and maintenance please

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