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CPAP Machine Choices

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There are many choices to consider when selecting a CPAP machine. Pictured: Zzz-PAP with Heated Humidifier.


CPAP (pronounced see-pap) is an acronym for Continuous Positive Airway Pressure. The term CPAP is used two ways. One way is literal, indicating a straight CPAP machine with a constant pressure. The other way is generic, indicating two other types of PAP machines as well, including bilevel PAP (with one pressure for inhalation and one for exhalation) and auto-adjusting PAP (APAP with self-adjusting pressure based on your body’s requirements , and auto-adjusting bilevel.) Other terms for a PAP machine are device, flow generator, or blower. The earliest treatment for Obstructive Sleep Apnea was a tracheostomy, cutting a permanent hole in the windpipe. The CPAP machine was invented in 1981 by Dr. Colin Sullivan, an Australian pulmonologist. Later the bilevel and AutoPAP were developed. Read an interview with CPAP’s inventor.

The term PAP indicates any type of Positive Airway Pressure machine. Compared to surgery, the PAP machine is a wonderful invention, a safe, relatively noninvasive and inexpensive way to restore you to health and happiness. Machine technology is evolving quickly; here’s a comparison to illustrate. Straight CPAP is like black and white TV, APAP is like color TV, and bilevel and PAP machines not yet on the market are like flat panel, plasma, and high definition TVs. In future PAPs, patients want better sensors, patient-centered software, better auto adjusting, exhalation relief, smart displays, heated hoses, integrated power supply, and smaller footprints. One difference between TVs and PAP is that a PAP is a medical device, not a consumer product. However, PAP extra features are not frivolous “bells and whistles;” they are features to make therapy more effective so patients don’t give up on it. See Machine Answers

Contraindications for PAP[edit]

Your doctor will assess medical reasons which may indicate not using PAP, involving previous or recent head injury, certain respiratory conditions or lung disease, recent ear, nose, or head surgery, vomiting, stroke (inability to maintain airway), seizures, severe cardiac arrhythmias.

Possible contraindications for the variable pressure auto-adjust mode may be epilepsy, central sleep apnea, stroke, and various heart and respiratory conditions such as Cheyne-Stokes respiration. A bilevel machine prescribed by an experienced sleep doctor may be a better choice.

PAP use may be contraindicated short term with a sinus or middle ear infection, severe ear discomfort, severe nosebleed, conjunctivitis, or skin abrasions caused by the CPAP mask. Consult your physician.


A doctor’s prescription is required by US federal law to rent or purchase a machine, whether through a Durable Medical Equipment (DME) or home medical equipment company or online, whether paid by insurance, Medicare, or bought outright by the user. Any doctor can write the prescription, your primary care physician or a sleep doctor. Get the prescription in hand so you can choose your provider, through insurance or online through insurance or online at your own expense. There are two options for prescriptions. One is to get a general prescription for a CPAP which can also be used for an APAP, since the insurance code is the same. Another option is to get a specific prescription for a certain brand and model, if you and your doctor think that will be more useful in working with your particular DME company. The DME should not refuse your doctor’s prescription for a particular brand and model in favor of a cheaper machine to increase their profit at the expense of your successful therapy. For example prescriptions see Suggested Specific CPAP Equipment Rx. For more on prescriptions, see Answers, Prescriptions.

CPAPtalk member Halley's mom says:

"Thanks to lots of good info I gleaned from this site, I asked my physician to specify a fully data capable CPAP machine so that I could monitor my progress. That's exactly what he wrote on the Rx, so I got the Elite II with no problem from the DME. So, you might want to check with your doctor to see if he/she will add that requirement to your prescription. Good luck!"


The choice of type, brand, and model of machine is both a medical decision and a patient-preference decision, best made as a collaborative decision between you and your prescribing physician. A sleep doctor will know your medical needs and should ideally, but not necessarily, have knowledge of brands and models of machines. You are the one who needs to use the machine all night, every night, for the rest of your life, so your agreement, cooperation, and comfort are essential. You can research machines at and manufacturers’ web sites, and perhaps through local, unbiased sources such as a hospital sleep lab. As you learn about equipment, bring that knowledge to your doctor’s appointment. You can anticipate your machine preferences and needs for adaptability and comfort.

The choice of a machine is best not left solely to a Respiratory Therapist (RT) at a Durable Medical Equipment/home care provider. The RT may know about various machines, but their inventory (and maybe knowledge) will be limited by the brands of machine carried by their company. For example, it’s said that Apria favors Respironics machines and Lincare favors ResMed machines because of their business contracts with those manufacturers. Your patient needs are not necessarily the same as the DME’s business deal or need to move inventory. (The same is true for masks.) The DME may be able to get other brands, but not initially suggest them unless you request it. In the end, your research and trial and error are the methods for finding the best machine for you, since each person is unique. For more, see Answers, CPAP Brands.

The top three PAP machine manufacturers are Respironics, ResMed, and Puritan Bennett.

Discussion thread on machine brands beyond the big three.

Data Capable machines[edit]

These machines can report AHI, leak rate, etc. to help you track and improve your therapy: Which machines can record data?

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

   * Respironics REMstar Pro M series
   * ResMed S8 Elite and Elite II
   * Puritan Bennett GoodKnight 420S and 420SP
   * Covidien/Puritan Bennett Sandman Info (not to be confused with the model named "Intro.") 

AUTOPAP ("autotitrating cpap" or "APAP") machines which record full data:

   * Respironics REMstar Auto M series -- with or without "A-Flex."
   * ResMed S8 Autoset Vantage and Autoset II
   * Puritan Bennett GoodKnight 420E
   * Covidien/Puritan Bennett Sandman Auto
   * DeVilbiss IntelliPAP AutoAdjust Travel CPAP with Smartflex

The older pre-M Respironics REMstar Auto (with or without C-Flex) and ResMed S7 AutoSet autopaps record full data. Note: The pre-M Respironics machines (autopap and cpap) are often referred to on this message board as the "tank" or "legacy" or "pre-M" models.

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

   * Respironics BiPAP Auto with Bi-Flex M series
   * ResMed S8 VPAP 

The older pre-M Respironics BiPAP Pro 2 with Bi-Flex and ResMed S7 VPAP III record full data.

Failure hazard of any PAP treatment[edit]

Most people on PAP therapy use straight CPAP machines, and about half of PAP users fail at continuing the therapy. Those who give up on PAP have increased risk for stroke, heart failure, obesity, diabetes, and other serious health conditions, as well as a diminished quality of life overall, including greater risk of car crashes. If further medical treatment is necessary because of the consequences of abandoning PAP treatment, this is extra cost for both the patient and insurance company.

Three main reasons for the high failure rate of PAP compliance may be 1) poor mask selection and mask fitting resulting in leaks, 2) lack of quality information for the patient about PAP equipment and therapy, and lack of support in adjusting to the therapy, and 3) lack of patient involvement in therapy equipment decisions and management of therapy. Other equipment problems are wrong pressure settings, discomfort from equipment problems (humidification, rainout/condensation in the hose, hose management, aerophagia/swallowing air, bed pillows).

Comfort in using the machine and good results from it are essential for continued use. With any PAP machine, if the machine is not preventing your apnea/hypopnea events (AHI) because your pressure settings are wrong or your mask leaks too much, or if it’s hard to exhale, or if the machine is incompatible with your breathing pattern, or if it’s so noisy it keeps you awake, or if it’s too bulky to take with you when you travel, you are risking successful therapy and a happier, longer life. This is where high quality equipment as well as good patient information can help you. Software can involve you in the therapy and give you information on correcting mask leaks and AHI related to pressure. An APAP machine and software can allow you and your doctor to fine-tune the pressure. People who take control of their therapy are those who succeed.

Selection Criteria[edit]

Selection criteria in order of importance for many people. What are your priorities?

1. Type of machine - CPAP, APAP (auto CPAP) or bilevel, with full data capability(software that measures more than just compliance or usage). The choice is based on both your medical needs and patient needs, since you will be sleeping with it all night, every night, for the rest of your life, and your life depends on it. An APAP machine provides two-in-one, since it can be used in either the APAP or CPAP mode. All APAP and bilevel machines are data capable. Only a few CPAP machines are data capable.

2. Software showing AHI (Apnea-Hypopnea Index of events per hour, AHI related to pressure, mask leaks, etc.). Not paid by insurance. Gives you and your doctor essential information to monitor and adjust your therapy, promoting success.

3. Heated humidifier with several temperature levels and passive (unheated) humidification; integrated (built-in) or stand-alone which can be used with another PAP if you get one. Keeps nose, mouth, throat healthier, reduces nosebleeds, required for a full face mask. Humidification is more comfortable for most, but not all, people.

4. Exhalation relief (called A-flex and C-flex in Respironics machines and EPR in ResMed machines). Briefly reduces air pressure on exhalation, making it easier to exhale, a comfort factor making it easier to sleep. Comfort is not a frill; it leads to adapting to and continuing the therapy. Those who have a higher prescribed pressure or who need more exhalation relief may require a bilevel machine. Some, especially those with low pressures, don’t need or want any exhalation relief.

5. Price, factoring in private insurance coverage, co-pays and deductibles, or Medicare, and pricing of equipment sold online

6. Size – weight, dimensions, portability

7. Features – smart LCD display, mask off alert, automatic (or manual) altitude adjustment, ramp or settling (gradual startup), AC/DC/DC power cord, international voltage, battery option, etc.

8. Ergonomics, ease of use – how to change various settings, LCD display size and readability, buttons, lights not too bright or too dim

9. Noise. Not usually a problem with current machines unless you are especially sensitive to noise. Noise level in decibels is listed in the user manual specifications. Normal conversation is 60 dB. A whisper is 15 dB. Most PAP machines are around 30 dB, much quieter than snoring. Noise is related to the individual machine; some are quieter, some more whiny. You could consider a quiet PAP machine as relaxing, soothing white noise, soft waves lulling you to sleep.

Trying a Machine[edit]

Trying a machine, rental, purchase. Even if you and your doctor are convinced that a certain machine will be right for you, and even if at your first visit to the DME company they offer to let you buy it on the spot through your insurance company (after you pay a deductible), avoid buying a machine at the very start of treatment before you try it. (There’s a possibility that an unscrupulous DME is taking advantage of your being an exhausted and uninformed PAP novice by selling you a low-end or outdated CPAP machine which costs them less than $300, while billing your insurance company top dollar, the same amount they would bill insurance for a high-end APAP machine which costs them less than $600. They make twice the profit by providing you with a cheap CPAP machine.) You need time to try it out the machine to be certain it will work for you. With experience, you may change your mind about which machine is best for you.

If a machine doesn’t seem to fit your breathing patterns or is noisy or doesn’t fit your needs, work with your doctor and try out different machines through rental at your DME, at another DME on your insurance plan, or at a sleep center. If your insurance and DME are already providing a machine but you want to find a better one through a one-month trial rental, it will be at your own expense. That’s less expensive than buying a machine and then finding out it doesn’t work. Find a good local DME company by asking a hospital sleep lab for recommendations. Then inquire about a monthly rental from them, with prescription in hand.

Most insurance companies require at least a two or three month wait before they will purchase a machine for you, to make sure you are “compliant” (adapt to using the machine at least four hours nightly). When you are certain the machine is the best for your needs, then is the time to buy rather than rent. A typical approach is to let the DME rent you what seems to be the best machine from your research and your doctor’s input. If it works well, let your insurance plan buy it for you in two or three months. It’s reassuring to own the machine that you depend on. You will probably need to phone the DME to initiate the purchase, if they have been making more money by renting it than selling it. First do the math to see if purchase is more cost effective for you than continual rental. Compare the local DME price with online prices and see what your insurance company will reimburse. With purchase, you are responsible for repairs, but most machines are fairly reliable, under a two-year warranty with an anticipated life of five years or more.

Discussion threads on rental from DMEs and buying:

There are many places to buy a machine. Find out which ones are covered by your insurance. Then compare your insurance costs (deductibles, co-pays) with buying on your own, online, to find which is less expensive. Places to buy a PAP machine:

  • Local branch of a large, national DME company, or small local DME company
  • Sleep lab or doctor acting as a DME
  • Online DME billing insurance
  • Online DME billing Medicare
  • Online DME for people paying at their own expense, which may or may not be reimbursable on their insurance, such as

More Info

Medicare guidelines[edit]

Medicare guidelines, which most insurance companies follow, allow for machine replacement every five years. That’s a relatively long time in a market that quickly develops better new technology, so you probably want an up-to-date machine that works the best for you from the start. For more see Answers, CPAP and Sleep Apnea Basics, Machines.


It helps enormously to have software so you can responsibly self-manage your therapy, with your doctor’s support, and monitor mask leaks and machine performance and track results. Using a PAP machine without software is like driving a car without a windshield and without an instrument panel. You may think you are on the road and getting there, but you’re really not sure; you just know you haven’t crashed yet. You may think you’re not speeding and have enough gas, but you’re not really sure. With a PAP machine with little or no feedback information, you may feel better or not feel better, but you have no other information.

If you’re not doing as well on PAP as you think you should be doing, and have no software, you and your doctor have very little information on what or how to improve. Does your mask leak? How much, acceptably or too much? Are you still having apneas (stopped breathing), hypopneas (partial breathing), and flow limitations or UARS (like small hypopneas in the nose and mouth) How many? Are you still in the severe, moderate, or mild range of the AHI (apnea-hypopnea index), or are you now in the normal range? Where in the normal range? At what pressure do you have the most and least apneas and hypopneas? When you make a mask change or adjustment, does it help or hinder? If your doctor makes a pressure change, does it help? Some doctors may be disdainful of PAP sensors and software, since they aren’t as sophisticated as sleep lab equipment. However, the smart PAP and software provide adequate night-to-night information to monitor and adjust therapy, when a full-blown sleep study isn’t needed or possible.

With a data capable machine and software, you have data on your Apnea Hypopnea Index, AHI related to pressure, flow limitation, volume of mask leaks, snores, etc. If you are computer literate, most PAP software is easy to use, even for those who aren’t computer experts. If your machine has data capability and a smart card, you can take the card to a cooperative DME for a printout sent to your doctor, and don’t need to buy software.

Warnings: 1) Not all machines are fully data-capable, so select one that is. 2) Some software records only compliance (usage) for the DME and insurance company’s benefit only, so make sure the software also records AHI, leaks, and pressure. Insurance won’t pay for software or a smart card reader, but you may be able to deduct them as a medical expense on your income tax. You don’t need a prescription for software. Software and readers can be purchased online often for less than $200 for both. Find Software.

Discussion threads on software:

Heated humidifier[edit]

In normal breathing, your nose warms and moisturizes incoming air. With the large volume of air forced into your nose (or mouth) by a PAP machine, your nose can’t keep up. Use of PAP leads to congested nasal passages in many people who weren’t previously congested. The addition of a heated humidifier makes PAP healthier and more comfortable, which makes it easier for you to adapt or be compliant. It helps you avoid nosebleeds and dry nasal passages and mouth and maybe even helps ward off colds. A heated humidifier is required for a full face mask for mouth-breathers or people who are temporarily using a full face mask because of a cold or allergies. For many people, a heated humidifier is more natural, comfortable, and effective than unheated. Some people prefer passive or passover unheated humidification, so they don’t turn on the heating element. Most humidifiers are machine model-specific and fit into the machine (integrated). You might consider a stand-alone humidifier, which works with any machine, if you anticipate having more than one machine over time. Sometimes a certain model of humidifier is known for leaking or being difficult to fill. Check with other users on for their product opinions. Do you have a deviated septum, nasal polyps, allergies, nosebleeds, or chronic sinus congestion that may make a heated humidifier medically necessary? Discuss use of a heated humidifier with your prescribing physician to see if it should be prescribed. A humidifier prescription is not required by law, but is required for insurance reimbursement. For more see Answers, Humidifiers.

Exhalation relief[edit]

Some people find exhalation relief makes therapy more comfortable because it matches their natural breathing patterns and they don’t have to fight incoming air pressure to exhale. It increases their compliance. Others don’t need pressure relief. Some Respironics models (both CPAP and APAP) have A-Flex or C-Flex with three settings. The machine senses exhalation and lets the pressure drop slightly and briefly, making it easier to exhale. The Flex feature has various levels and can be easily turned off. See Respironics flex technology

Flex discussion threads:

RedMed has EPR (expiratory pressure relief) available only in its straight CPAP machine. See

People who need a lot of exhalation relief may need a bilevel machine.

Hoses (tubing) PAP machines are dispensed with a hose to connect mask to machine. Hoses are a standard diameter to fit any machine and mask. The standard hose is 6 feet in length. Hoses also come in 10 feet and 18 inch extensions. A few machines or masks require a nonstandard hose, see [url][/url] People who experience rainout (condensation in the hose) or who want to maintain PAP heat and humidity levels in a cool bedroom buy the Australian SleepZone heated hose, . There are hose-to-hose connectors and right-angle hose connectors.

Ramp or settling allows the user to start treatment at a lower pressure and as they fall asleep, the pressure slowly rises. This is a comfort setting and can be from 0 to 45 minutes on most PAP machines. Ramp is more appreciated by beginners. Sometimes the lower ramp pressure setting is too low to clear exhaled carbon dioxide from the mask, so it’s not comfortable unless it’s adjusted upward. Many experienced PAP users find ramp unnecessary.

CPAP MACHINES(constant pressure)

Advantages of straight CPAP[edit]

1. A straight, constant pressure setting delivers the best results for many people. (However, the versatile APAP is two machines in one and can be set to a straight CPAP mode.)

2. Except for some of the features noted below and in the comparison charts, all CPAPs have a standard operation and give similar results. There are few performance variables, which makes it easier for your doctor to prescribe a machine and predict the machine’s performance. Your experience with it is another matter. Since CPAPs have been around the longest of the three types of machines, more research has been done on them and some doctors are more familiar with them than the advanced technology APAPs or bilevels, so may tend to prescribe CPAPs more frequently.

3. Some Respironics, ResMed, and Puritan Bennett machines have software to track your results (not just compliance). Other brands do not.

4. Some Respironics and one ResMed straight CPAP model have pressure relief for exhalation. Other brands do not.

5. CPAPs are the least expensive of the three main types of PAP machines. Prices start about $220 to $500, without a heated humidifier. The top end overlaps with the price of some APAPs. Depending on your insurance deductibles and co-pays for the machine and need for subsequent sleep studies because you don’t have an APAP with software, getting a less expensive CPAP machine may be to your financial advantage or not.

6. For backup when electric power fails, or for travel, camping, or armchair naps, there are choices of small and light CPAP machines with or without integrated rechargeable batteries and a DC port for DC power supply from batteries. (APAPs and bilevels also can run on DC power.)

7. If you already have a low-end or high-end CPAP machine and it’s continuing to work well for you, you feel good all day, and your blood oxygen saturation rates are good (measured with an overnight recording pulse oximeter), then you may already have the best machine for you.

Disadvantages of straight CPAP[edit]

1. You may need a different pressure to lower your AHI. A) Your titrated pressure may be wrong or have changed. The sleep study titration (finding a pressure setting) was probably only a few hours of one night, in an unnatural setting which some people describe as the worst night of their life. See Reasons why your titrated pressure may be wrong. B) If your weight goes up you may need a higher pressure setting; if it goes down, a lower setting. If you have CPAP and software and work with your doctor, you can work to improve your pressure setting, but not nearly as easily as if you had an APAP machine with software, which can also be used in the straight CPAP mode. C) You may need a different pressure during the night when sleeping on your back or side, when in REM sleep, after using alcohol or sedatives, or with nasal congestion. A straight CPAP machine cannot automatically adjust to the need for pressure changes while you are sleeping. If your pressure is not correct, you will not be getting the full benefits of therapy and won’t feel as good as you would with the proper pressure setting, and you may be tempted to give up. Only an APAP machine or auto-adjust bilevel machine can match your changing pressure needs throughout the night.

2. Because most straight CPAPs don’t provide optional software data, they don’t encourage the user involvement that a smart APAP machine does. Patient involvement is essential for buy-in and commitment leading to successful continued use.

3. If your doctor is informed about CPAP but not about the newer technology and advantages of APAP and bilevel, and is not tuned in to your individual user needs and preferences, the straight CPAP they prescribe may not be the best match for you.

4. Although the initial price may be somewhat lower, if a CPAP is your sole machine, depending on your insurance and budget, price may not be the most important factor. If your insurance deductible is the same for a basic or advanced machine, and your health depends on its successful use, you may be far better off with an advanced machine. If, by having a less expensive CPAP without software, you require additional sleep studies, that may add to your overall insurance deductible cost.

CPAP comparison chart[edit]

CPAP comparison chart of various brands and models

See the best selling CPAP machines at this online DME for self-paying customers at How many of these people already have an APAP machine at home and are buying a small CPAP as a backup or for travel?

APAP MACHINES (Auto-adjusting CPAPs also known as auto-titrating, self-adjusting, or auto CPAPs)

APAPs (pronounced A-paps) are the new generation of the original CPAP machines. They are smart machines which use sensors to automatically adjust pressure throughout the night if your body needs more or less pressure. In addition, when set in APAP mode with smart capability, the machine does a mini-sleep study on you every night, in the comfort of your own bed, helping you and your doctor adjust your therapy. Many APAP users find that the newer, adjustable technology of APAP provides better nightly therapy than straight CPAP. (If they find they do better on straight CPAP, they then switch their machine to the straight CPAP mode.)

For information on APAP and BIPAP Machines view:



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