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CPAP Equipment: CPAP Machines: Auto-Adjusting Machines

Auto Adjusting CPAP Machine

Auto Adjusting CPAP Machine Overview

Auto Adjusting CPAP Machines or APAPs adjust to your ideal pressure on a breath by breath basis. They can accommodate pressure changes from weight gain or loss, alcohol before bed and changing sleeping positions during sleep. They are very popular among savvy online shoppers for their advanced air flow settings and their support of therapy tracking software, off grid power options and heated humidification.

Auto-Adjusting Machines FAQs

What is an APAP Machine?

An APAP (Automatic Positive Airway Pressure) machine automatically adjusts on a breath by breath basis to blow the minimum pressure needed to keep your airway open during sleep. This allows your machine to provide you with your ideal pressure nightly.

APAPs tend to be more advanced than CPAPs in that they normally offer more therapy tracking information and more comfort features. You can learn more about therapy tracking information in our Software section of the Learning Center.

Every APAP machine can be placed in a CPAP mode to blow one straight pressure like a CPAP. However, no CPAP can automatically adjust pressure like an APAP. An example of an APAP machine is the DeVilbiss IntelliPAP AutoAdjust that comes with built in Smart Code therapy tracking software.
IntelliPAP AutoAdjust CPAP Machine

Why might I prefer an APAP machine?

Some CPAP users find it more pleasant to breathe with an APAP than with CPAP. The pressure delivered by an APAP machine automatically changes as needed to deliver the minimal pressure required to maintain the airway. The pressure delivered by a CPAP machine is set to a single pressure, the highest necessary to keep the airway open as determined during the sleep study. This is the case even when the higher pressure is needed only a fraction of the time.

What are data capable machines?

Data capable machines track your therapy progress and performance over time. Therapy data can be used to spot issues and used to see how changes to your CPAP setup effects your overall treatment. You and your doctor can use the therapy information to make changes in your setup. Some changes might be altering the mask or fit or increasing or decreasing your pressure to see if your therapy performance improves to ensure you are getting effective treatment.

The data capable machines not only let you know how many hours the machine was used, like pure compliance tracking machines, but also tracks advanced information such as AHI, Leak Rate, and Average Pressure (if using an APAP).

Depending on the machine, the information can be reviewed or accessed

  • On Machine Screen Display. Machines that display advanced tracking using the on machine display allow for fast review of therapy metrics. Many people like to use the on screen display to check every morning. Information such as AHI and leak rate for the previous night are displayed allowing the user to make adjustments such as mask fit. The information provided on the on machine screen is usually average values over different time frames, such as 1 day (last night), 7 night, 30 nights, etc.
  • SmartCode. SmartCode is a code that is accessed through the machine's display. This code is then inputted into the machine's product page on CPAP.com and a summary report is generated. You can see a Sample Report here. An example of an on machine display with the SmartCode is shown below. The only machine with advanced data capable SmartCode is the IntelliPAP AutoAdjust. The SmartCode provides therapy data averages for the following time frames: 1 day (last night), 7 day, 30 day, 90 day, and cumulative. This is like the information provided from the on screen display, however the information is displayed in chart format instead of a single number at a time. SmartCode Display
  • Optional External Software. Some machines have external software that can be used to download the data from the machine for detailed analysis. External software, unlike the on machine display or the SmartCode, allows you and your doctor to look into any night of use. Further, the information for any given night can be broken down hour by hour. This allows you and your doctor to look for patterns in your data through the night; for instance, do you tend to have more apneas in the early morning? Or do you begin to breathe with your mouth open in the middle of the night? Some external software is available for sale to patients, other software is only sold by the manufacturer to sleep professionals. External software may require other components to be able to get the information from the machine onto you computer with the software installed.

What are compliance tracking machines?

Compliance tracking machines only track the numbers of hours the machine is used. These machines do not track any advanced information such as AHI or leak rate.

Compliance machines are basic machines which the manufacturers made to be able to track usage hours. Compliance tracking machines are a manufacturer response to Medicare requirements that mandate DME (Durable Medical Equipment) providers show the Medicare patient used the equipment for the required minimum number of hours set by Medicare. DME providers cannot continue to be paid by Medicare without this information.

There is one billing code for all CPAP and APAP machines. Therefore a DME will be paid the same from Medicare or insurance whether they provide a patient with a more expensive machine that is data capable with more comfort features or a basic compliance tracking machine. Therefore, compliance tracking machines are the most common type of machine that is provided to patients through local DMEs.

There is software created to show the compliance information from the machine, however CPAP.com does not recommend purchasing this software. This data will only tell you how many hours you actually used the machine. It will not tell you how effective your therapy is.

What data capable machines are available?

CPAP machines which record full data (such as AHI and leak info):


AUTOPAP ("Autotitrating CPAP" or "APAP") machines which record full data:


BILEVEL ("BiPAP") machines which record full data:


CPAP Machines that only record Compliance Data (Hours Used) are:

  • IntelliPAP Standard Travel CPAP Machine
  • PR System One REMstar DS150 CPAP Machine
  • PR System One REMstar Plus CPAP Machine with C-Flex
  • PR System One REMstar 60 Series Plus CPAP Machine with C-Flex
  • PR System One REMStar 60 Series SE CPAP Machine
  • S9 Escapeâ„¢ CPAP Machine with EPRâ„¢
  • SleepEasy II CPAP Machine with Built In Heated Humidifier and C-Flex
  • SleepStyle 234 CPAP Machine with Built In Heated Humidifier

    How do I choose the machine that is right for me?

    We provide our customers with many tools to make informed decisions about their machine purchases. Options include:

    • Calling a CPAP Expert Toll Free. 1-800-356-5221.

    • Comparison Charts. These charts compare available machines, feature by feature. If you don't know the meaning of a feature, click on the question mark for a definition. Click on the image or name of the product for more detailed product information, pictures and resources.

      CPAP Comparison Chart

      APAP Comparison Chart

      BiPAP Comparison Chart

    • Help Me Choose Guide. We created a guide to help you select the right machine according to your preferences. The guide asks you a series of questions regarding your preferences and your prescription. Based on your answers we provide you with a comparison chart of the machine that meet your criteria. Get started here:

      Help Me Choose - Machine

    • Browse Our Machine Product Categories. These categories show each machine our company offers, ranked by popularity. Popularity is determined by a mix of sales data and our in house opinion of the quality of the machine based on our experience and customer feedback. The best products float to the top of our categories.

      CPAP Machine Category

      APAP (Auto Adjusting) Machine Category

      BiPAP (Two Pressure) Machine Category

    How can I compare different machines?

    We work very hard to provide many different ways for our customers to compare products. Here are the machine product guides we have created and maintain:

    • CPAP Machine Comparison Guide. This guide stacks up every CPAP machine we sell, feature by feature. If you don't know the meaning of a feature, click the question mark for a definition. The links below will take you to the most popular CPAPs, or all CPAP machines we sell.

      Compare Most Popular CPAP Machines

      Compare All CPAP Machines

    • Auto Adjusting Machine (APAP) Comparison Guide. This guide stacks up every APAP machine we sell, feature by feature. If you don't know the meaning of a feature, click the question mark for a definition. The links below will take you to the most popular APAPs, or all APAP machines we sell.

      Compare Most Popular APAP Machines

      Compare All APAP Machines

    • BiPAP, VPAP and BiLevel Comparison Guide. This guide stacks up every BiPAP machine we sell, feature by feature. If you don't know the meaning of a feature, click the question mark for a definition. The links below will take you to the most popular BiPAPs, or all BiPAP machines we sell.

      Compare Most Popular BiPAP Machines

      Compare All BiPAP Machines

    What comes with my machine?

    Machines come with a six foot hose, power cord, at least one filter, and manuals. Most manufacturers include a carrying case which is designed specifically for their equipment. CPAP / BiPAP / APAP machines do not come with a delivery system or mask. CPAP Masks must be purchased separately.

    To see the list of what specifically comes with each machine, you can browse for a machine. Then on the product page, click the "Specs" tab to see a full list of what comes with the machine.

    What is ramp?

    The ramp button on a machine is a feature that allows for a gradual pressure build-up to your prescribed pressure. The feature is enjoyed by those with high pressures because they ease up to their pressure.

    What is exhalation relief?

    Exhalation relief is a comfort feature offered by two manufactures which reduces the air flow at the time of exhalation making the breathing process more natural.

    • Respironics = C-Flex, C-Flex+, A-Flex and Bi-Flex
    • Resmed = EPR (Expiratory Pressure Relief)

    What is A-Flex?

    A-Flex is a form of exhalation relief which helps the air pressure from an APAP machine mirror a person's breathing. Like C-Flex, A-Flex provides flow-based pressure relief at the beginning of exhalation. Like Bi-Flex, A-Flex softens the pressure transition from inhalation to exhalation to provide additional comfort in an auto-CPAP mode.

    A-Flex Easy Breathing Technology Visual Graph A-Flex Easy Breathing Technology Visual Graph

    What is Bi-Flex?

    Bi-Flex is a feature that makes breathing back against CPAP pressure easier to do. Bi-Flex pressure relief technology offers pressure relief at the transition from exhalation to inhalation, at the transition from inhalation to exhalation, and during exhalation to make BiPAP therapy more like natural breathing.

    Bi-Flex Easy Breathing Technology Visual Graph Bi-Flex Easy Breathing Technology Visual Graph

    What is C-Flex?

    C-Flex is a pressure relief feature that makes breathing back against CPAP pressure easier to do by reducing the pressure at the beginning of exhalation and returning to therapeutic pressure just before inhalation. Independent studies conducted by leading universities indicate that patient comfort, and therefore, patient CPAP compliance, is higher with machines that use C-Flex. C-Flex is a technology invented by Respironics, is proprietary, and is not available on other brands of CPAP Machines.

    C-Flex Easy Breathing Technology Visual Graph C-Flex Easy Breathing Technology Visual Graph

    C-Flex vs. Traditional CPAP: Brown University Study

    cpaptalk.com Interview, C-Flex in the Remstar Pro and Remstar Auto

    What is C-Flex+?

    C-Flex+ is an improved pressure relief technology over the previous C-Flex technology. Like C-Flex, C-Flex+ reduces the pressure at the beginning of exhalation. Like A-Flex, C-Flex+ softens the pressure transition from inhalation to exhalation to provide additional comfort in fixed-CPAP mode.

    C-Flex+ Easy Breathing Technology Visual Graph C-Flex+ Easy Breathing Technology Visual Graph

    What is the difference between Bi-Flex and C-flex?

    C-Flex only works at the start of an exhale. Bi-Flex works during the transition from exhalation to inhalation, the transition from inhalation to exhalation and during exhalation.

    What is EPR with Easy-Breathe?

    EPR (Expiratory Pressure Relief) is a pressure relief feature developed by ResMed. EPR reduces pressure during exhalation in order to make breathing more comfortable. Easy-Breathe technology applies a smooth waveform that helps make breathing feel more natural.

    EPR with Easy Breath Manufacturer Fact Sheet

    Are prescriptions required for mask, machine and/or humidifier purchases?

    Yes. Federal law requires we have a valid prescription on file before we ship your mask, machine and/or humidifier.

    We provide many easy ways to get your prescription:

    • We can request your prescription for you! When you checkout, just let us know you would like us to request your prescription, or you can log into your account to have us request your prescription.
    • Fax your prescription to our Toll Free fax number: 1-866-353-2727, or our international fax number: 713-541-7370
    • Email your prescription to cpap@cpap.com
    • Upload your prescription in your account, under the prescriptions section
    For more information on prescriptions, please see our Prescription Section of the Learning Center.

    What does an APAP prescription need to say?

    An APAP prescription must contain all of the following information:

    • One of the following words or phrases: "APAP", "AutoPAP", "AutoSet", "Auto CPAP", "Auto Adjusting CPAP", "Self Adjusting CPAP", "CPAP" or "Continuous Positive Airway Pressure" or similar term.
    • Your physician's contact information
    • Your physician's signature
    • The patient's full name

    An APAP prescription may contain the following information:

    • Your pressure range (Optional, Not Required)
      • Example: 4-20 CM/H20
      • Example: 4-20
      • Example: 6-18 CM/H2O
      • Example: 6-18

    CPAP prescriptions are accepted for Auto Adjusting (APAP) Machines.

    Which CPAP masks work on which machines?

    All CPAP masks work with all machines.

Do all CPAPs use filters?

Yes, all CPAPs use at least one filter that is usually a type of foam material and washable. Some CPAPs offer finer filtration with the addition of a disposable paper filter.

Cleaning and changing filters is the only maintenance required for a CPAP machine.

The filters are located at the back of the machine at the air intake. The image below shows the black foam filter at the back of the Everest 3 CPAP Machine.

How often should I clean my filters?

Washable foam filters should be cleaned as soon as they become discolored. Manufacturers recommend foam filters be rinsed weekly under clear running water and allowed to air dry before being reinstalled in the machine. If the machine is used in a very dusty environment, the foam filter may require more frequent cleaning.

Disposable filters are not intended to be cleaned but rather changed out, disposing of the used filter. Manufacturers recommend changing the disposable filter once a month, more frequently if used in a very dusty environment.

Can I travel by air with my CPAP?

Yes. CPAP therapy should be used every night. In the USA, your CPAP machine and mask are not counted as a carry on item for air travel. Some locations in Asia and Europe may count it as a carry on, but all will allow it. Check with the carrier you are using for travel.

Helpful Links:

Air Travel: Call your airline. Each airline has a different policy on whether or not you can use your CPAP while in flight, and if they have a power source available.


Cruise: Electrical outlets may not be available near the bed. Take an electrical extension cord along to ensure you can plug in the machine. Many cruise lines will provide distilled water. Call your cruise company for their specific policies and amenities regarding CPAP equipment.


Here is a letter from Resmed on the topic:

ResMed Travel Letter

What travel tips should I know?

CPAP therapy should be used every night. Your CPAP or BiPAP machine and equipment should go with you on trips. There are some tips to help with your travel:

  • Remove Water From The Humidifier. If you are going to take your CPAP humidifier with you, remove ALL water from the humidifier chamber. Water left in the humidifier chamber can be tipped into your machine and cause damage.
  • Accompany Your CPAP Through Security. Stay with your CPAP machine. When going through security, security agents will usually need to inspect the CPAP separately. Ask to stay with the CPAP. This way you can watch them handle the CPAP machine, and you can make sure all of your parts (cords, masks, chambers, filters) get back into the bag.
  • Plan Your Power Needs. Know what type of power your CPAP requires. If you are going to use a battery, make sure you have all the parts needed to safely run the CPAP on battery power. If you are traveling abroad make sure you have an international adapter plug. Check out the Power Solutions section of the FAQ for more information.
  • Identify Your CPAP as Medical Equipment. To help move through security easier, put a Medical Equipment tag on your CPAP bag. We offer a Medical Equipment Luggage Tag.
  • Carry a Medical Alert Card. Although this is good to have when traveling, it is also good to always carry a Medical Alert card in your wallet which lets emergency personnel know that you have obstructive sleep apnea. We offer a Medical Alert card.
  • Pack Your Power Cord. Just like people commonly leave cell phone chargers at home or in the hotel, we frequently get calls from travelers who have left their CPAP power cord. Check to make sure your cord is packed with your machine before you leave home and when heading back home.
  • Bring Spare Parts and Back Up Mask. Like the power cord, items get left behind or misplaced while on the road. Having backup parts and a back up mask will make sure that you are not caught without equipment.
  • Call Us If You Leave Something. CPAP.com delivers all over the US and to most international destinations. This includes to hotels and resorts. We also have expedited shipping options. If you are in a bind, give us a call 1-800-356-5221.

What maintenance is required on machines?

The only care a CPAP or BiPAP machine requires is to clean or change the filters at the air intake. This keeps the internal parts from accumulating dust. Fine paper filters should be changed out every 30 days, or when they appear soiled. Foam washable filters should be rinsed with clear running water once a week, allowed to air dry, and reinserted.

There are some other suggested actions to care for your machine:

  • Keep the area around your machine clean by removing any dust from the area to improve the air quality delivered to your machine and you.
  • Keep the air intake of the machine unblocked. Curtains, bedding, and papers can easily block the air intake of your machine, reducing the airflow.
  • If a humidifier is used with your therapy, do not pick up the machine with the humidifier attached. With most machines it is easy to spill water from the humidifier chamber into the machine causing damage. Manufacturer warranties are voided by water damage to the machine. To avoid this, remove the chamber from the humidifier and then remove the humidifier from the machine rather than transporting them together.
  • If a humidifier is used you should empty the water from the chamber every morning. Accidents happen. If a family pet or family member moves the machine and humidifier with water in the chamber it is more likely that water could be spilled into your machine. Water damage to a machine voids the manufacturer warranty.

How can I find replacement parts for my CPAP machine?

Wondering which filters work for your machine? Or trying to find the right replacement power cord? To find what parts are compatible with your machine or to find what parts of your machine are replaceable you can:

  • Use our Replacement Part Wizard to identify your machine and see all the related parts.
  • Browse for your machine and then click the "Replacement Parts" button on your machine's product page.

How do I change the pressure setting of my machine?

When a physician orders a pressure change, or a patient moves to an area with a very different altitude and does not have an altitude compensating machine, there are a number of ways to ensure you are receiving CPAP therapy at the correct pressure.

Sleep laboratories and sleep disorder centers may be willing to make this pressure change. Just call a big local hospital or ask you physician for sleep lab phone numbers. Be sure to take your prescription.

A second way is to do it yourself. We sell manometers that are very portable, accurate, and simple to use. All the machines we sell come with instructions on how to set pressure to physician orders. Most patients have little trouble doing this themselves. If you need help we can talk you through the procedure.

Gauge Manometer (for pressure measurements)

Fisher and Paykel Water Column CPAP Manometer with HC325 Chamber

A third option is to ship the machine to us with the new prescription. We will set it and ship it back.

It is the law and good common sense to run all sleep disorder devices at the prescribed pressure. If you think your prescribed pressure is wrong, talk to your physician.

What type of power does my CPAP need?

Most CPAP and BiLevel machines today are designed to operate on both AC and DC battery currents. In the United States, the AC current from a wall outlet is 110 volts. Overseas, the AC current is usually 220 or 240 volt. Most batteries produce 12 volt DC current.

We include information about the power needs and capacities on the CPAP.com pages our products. Please see the "Power" tab on any machine product page for this information. You can also see a summary of the voltage range and whether it is DC capable on our Compare Charts.

Here is a video explaining differences in power cords and power supplies of various CPAP machines:

Will my CPAP operate on DC / battery power?

All CPAPs will operate on DC power with the use of an inverter to change the current from DC to AC before it reaches the machine. However, many will operate on DC power without the need for an inverter, just a power cord that plugs into the CPAP and ends in a cigarette lighter plug.

Inverters do require a lot of power. If you need to use an inverter to run your machine on battery power, the inverter will probably take about half the life off the battery.

To determine if your CPAP will operate without an inverter, look for a DC outlet on the machine, either at the back or on the side, with a single opening directly in the center. It should be labeled "DC Power" or similar term. You can also review our Compare Charts to see if your machine has a optional DC cable option.

Here is a video describing different DC cable and battery options for various machines:

How do I prepare for power outages with CPAP?

There are a lot of back up battery choices out there that can give you peace of mind in case of a power outage. The Transcend Travel CPAP Machine has Battery Options available for that can set up as a fail-over, back up battery. Review the "Power" Tab on the machine page.

CPAP.com sells battery packs to accompany your machine if an integrated battery is not available. Visit CPAPtalk for more advice specific to your needs, or view this past thread on the topic here.

Can I use my Heated Humidifier with my machine if I am running on Battery Power?

Using a heated humidifier on a 12volt battery power source will significantly reduce the amount of power provided. In most cases, usage is reduced to less than half the estimated operational time. CPAPs or BiPAPs requiring inverters reduce the power time even more.

Please note that some heated humidifiers are not capable of being operated on 12volt battery power sources. The later M Series heated humidifiers with the 6'' 'pigtail' connectors are capable of running on 12volt DC power sources. Earlier model M Series heated humidifiers without the pigtail are not 12Volt capable, nor are the Legacy model REMstar and stand-alone H2 humidifiers.

For optimum performance of your battery, plan to use your CPAP without the heated humidifier. You may also have the humidifier connected and filled with water, but without the power turned on. This changes a typical heated humidifier into a passive humidifier.

We suggest testing the battery setup you are planning to use with your machine in advance. To determine the actual amount of power time you will receive and whether or not heated humidification is required for your comfort, test the battery at home before traveling.

Will my CPAP operate overseas?

An adapter may be required to plug a US power cord into a wall outlet in a foreign country. CPAP.com sells an assortment pack of World Traveler Power Adapter Plugs, which allow CPAP machines to plug into different types of wall sockets found in different countries.
All the models CPAP.com sell contain power converters that enable the machine to operate on any AC current from 100 to 240 volts without any adjustment.

What type of battery should I use?

For longer battery use, we suggest a deep-cycle marine battery. A CPAP set at 10cm will usually run for about three nights before having to recharge a deep cycle marine battery. A car battery will usually run a machine for 8 hours and still start the car.

There are small, portable battery packs that will operate a CPAP set at 10cm for at least one night, or about eight hours. CPAP.com sells full battery kits that come with everything needed to run your machine off battery power including the right cables needed for your machine and a battery. You can find the battery kit for your machine here. On each battery kit page, you can input your machine and pressure setting to see an estimate battery life for your machine.

How do I use a battery to operate my CPAP?

First you need to determine if your machine is configured to operate on DC power and has a DC power outlet. If your machine does have a DC power outlet and you want to run your marine battery, then you will need the correct DC cable for your machine and an adapter cable that fits over the cigarette lighter plug and ends in alligator clips.

CPAP.com sells complete battery kits with everything you need for your machine including the right cables for your machine and the battery. You can find the right battery kit for your machine here.

If your machine does not have a DC power outlet, then you will also need an inverter to be able to run your machine on battery power.

If you have questions about the specific power needs of your machine, review the "Power" tab on your machine's product page, or give us a call at 1-800-356-5221.

How can I get help from a CPAP Expert?

  • By Live Chat: Click on the Chat now field in the lower right hand corner of the CPAP.com page. If after hours, click Leave a message to enter your question and we will get back in touch with you.
  • By Phone: 1-800-356-5221 (8 AM - 10 PM CST Mon-Fri; 8 AM - 6 PM CST Sat)
  • Email Us: cpap@cpap.com
  • Ask A Question: Question Submission Form
  • By Fax: 1-866-353-2727

Why do I wake up feeling bloated with air in my stomach and intestines?

Bloating is a sign that you are swallowing the CPAP air. There is no real medical solution, but we have found that sleeping position may be a factor. Try sleeping as flat as possible first, even without a pillow. If that position doesn't help, try sleeping on your side or elevated, whichever one you don't sleep in now.

If changing your position doesn't resolve the problem, talk to your doctor about the possibility of lowering your pressure a bit. It may let a few apneas through, but the trade-off might be worth it.

What are the CPAP, BiPAP and Sleep Apnea related CPT or billing codes?

  • A7034 is Nasal Mask
  • A7034 is Nasal Pillow Mask
  • A7030 is Full Face Mask
  • A7027 is Hybrid Mask
  • A7044 is Oral Interface Mask (Oracle)
  • A7035 is Headgear for Mask - Any Style
  • A7036 is Chinstrap - Any Style
  • A7032 is Replacement Nasal Mask Cushion
  • A7033 is Replacement Nasal pillows
  • A7031 is Replacement Full Face Mask Cushion
  • A7028 is Replacement Hybrid Mask Cushion
  • A7029 is Replacement Hybrid Mask Nasal Pillow
  • A7046 is Replacement Humidifier Chamber
  • A7037 is Tubing / Hose - Long & Short Tubes
  • A4604 is Heated Tubing
  • A7038 is Disposable Filter (White / Paper)
  • A7039 is Washable Filter (Gross Particle / Foam/ Black)
  • E0601 NU is CPAP Purchase
  • E0601 NU is APAP Purchase
  • E0470 NU is BiPAP Purchase
  • E0470 NU is BiPAP Auto Purchase
  • E0471 NU is BiPAP ST Purchase
  • E0471 NU is BiPAP Auto SV Purchase
  • E0562 NU is Heated CPAP Humidifier
  • E0561 NU is Passover or Cool CPAP Humidifier
  • E0601 RR is CPAP Rental
  • E0601 NU is APAP Rental
  • E0470 RR is BiPAP Rental
  • E0470 RR is BiPAP Auto Rental
  • E0471 RR is BiPAP ST Rental
  • E0471 RR is BiPAP Auto SV Rental

E1399 is Miscellaneous and is used for other CPAP items.

What is the difference between C-Flex and A-flex?

C-flex drops the pressure on exhale only. A-flex drops the pressure on the exhale but also helps with the transition from inhale to exhale.