What to Look for in a CPAP Machine
By Andrew Senske, President CPAP-Supply.com
Last Updated 06/22/2010 12:02:00 PM

Looking at a CPAP machine comparison chart, or scanning through the list of CPAP machines on our website is a good way to learn about the different types of CPAP machines we offer. But to learn about all the features and designs aviailable would require considerable effort. Below, you'll find our list of features and designs to be considered when buying a CPAP machine. In other words, it's our list of what to look for in a CPAP machine.

1. Machine Type
These are the two main types of CPAP machines - standard and automatic. A standard CPAP machine blows at the prescribed pressure all night long, regardless of the patient's actual needs. An automatic CPAP machine fluctuates within a pressure range, detecting all the patient's flow limitation events (i.e. apneas, hypopneas, and snoring events) and responding accordingly to those events.

A bilevel machine allows for two pressure settings - a higher inhalation pressure and a lower exhalation pressure. Bilevel machines are generally suited to patients who have a particularly high prescribed pressure, or who have other respiratory issues which makes it difficult to breathe out against the influx of air. There are standard and automatic bilevel machines so bilevel machines could be considered a subcategory of the more general "standard" and "automatic" categories. Bilevel machines are generally more expensive than standard and automatic machines.

2. Pressure Range
Most CPAP machines have a pressure range of 4 cm H2O to 20 cm H2O. The DeVilbiss IntelliPAP range is 3 cm H2O to 20 cm H2O. The zzz-PAP pressure range is 4 cm H2O to 18 cm H2O. Some bilevel machines have a maximum pressure of 25 cm H2O.

3. Ramp
The ramp feature allows the patient to start the CPAP machine at a lower pressure than that prescribed, so that the patient doesn't get blasted with air while he's trying to fall asleep. For example, if the prescribed pressure is 10 cm H2O, the ramp start pressure can be set as low as 3 or 4 (depending on machine model). Then the machine will start at the lower ramp start pressure and will gradually increase to the prescribed pressure over a specified period of time. On most CPAP machines this time can be adjusted from anywhere between 0 (no ramp) to 45 minutes.

Automatic machines have the ramp feature, but if the low pressure setting on the machine is also the minimum pressure supported by the machine, then the ramp feature becomes irrelevant, because the machine is already starting out at the lowest possible pressure. For example, if you have an automatic CPAP machine with a supported pressure range of 4 cm H2O to 20 cm H2O, and a low pressure setting of 4 cm H2O and a high pressure setting of 12 cm H2O, then the ramp feature will not be used because the CPAP machine cannot blow at a pressure below 4 cm H2O.

4. Exhalation Pressure Relief
This is a feature that makes a standard or automatic CPAP machine function like a bilevel machine. Read our in-depth article on exhalation pressure relief for more information on how the feature works.

5. Sound Output
All newer CPAP machines are very quiet, but some are more quiet than others. Although the majority of noise you hear while using CPAP therapy is the sound of air rushing through the tube, the quietness of the motor is an important factor to consider. The ResMed S9 models are the quietest we sell at about 24 decibels, followed closely by the ResMed S8 II models and the DeVilbiss IntelliPAP models.

6. Data Card
Many CPAP machines either come with a data card or support the use of a data card that can be purchased separately. On most standard machines the data card records only basic compliance information like hours of use and number of sessions. All automatic CPAP machines with data card capability record basic compliance information along with detailed flow limitation event detection data and pressure data. Some employers (like trucking/freight companies) may require an employee who uses a CPAP machine to provide compliance data periodically. This basic compliance information is generally available through the LCD screen on the CPAP machine.

7. Carrying Case
With one exception (SleepEasy), every CPAP machine we sell comes with a carrying case. While each carrying case is adequate, some are better than others. For example, the DeVilbiss IntelliPAP carrying case simply has no room for a mask if you're also carrying the humidifier, tubing and power cord. With this particular carrying case, you should either leave the humidifier home when you travel, or be prepared to stow your mask somewhere else. Overall, it's a great case, but it's small. The ResMed cases look similar to laptop bags, and the newer Respironics cases look more like they're designed for hauling around big loaves of bread.

8. Power Configuration
All the CPAP machines we sell have universal power supplies that work with power inputs from 100 Volts to 240 Volts.

Nearly all new CPAP machines are 12V machines that have a transformer either in the machine or in the power cord which converts 110V from the wall outlet to 12V. On machines like this, all that's needed to run from a 12V battery is a 12V cord. The ResMed S8 and S9 machines require a special 12V cord. A couple of current CPAP machines aren't 12V devices (zzz-PAP and SleepEasy), so an inverter would be required to change the 12V output from a battery to 110V input for the CPAP machine.

9. Size and Weight
Many newer CPAP machines are extremely small and well-suited for traveling, especially the zzz-PAP machine which is the smallest machine available. Besides taking into consideration the overall size and weight of a CPAP machine and humidifier, it's important to know that most CPAP humidifiers can be removed from the CPAP machine. There are some CPAP devices, however, that have permanently built-in humidifiers. Our CPAP machine comparison chart shows you not only the weight of a CPAP machine, but the entire weight of the machine, power cord, manuals and carrying case.

Consider the dimensions and overall design of a CPAP machine when thinking about setting it on your night stand for the next several years.

10. Reliability and Warranty
All CPAP machines have at least a 2-year warranty, and all CPAP humidifiers have at least a 1-year warranty. The DeVilbiss IntelliPAP machines, which are among the most reliable machines we've sold to date, have a 3-year warranty, and the IntelliPAP humidifier has a 2-year warranty. Not all warranties are the same, though. ResMed and Respironics tend to replace defective machines immediately without first receiving them back and testing them. While DeVilbiss machines are very reliable and are covered by the longest warranty in the industry, DeVilbiss requires a defective machine to be sent back for repair, instead of offering immediate replacement. We facilitate all warranty replacements and repairs for our customers. None of the manufacturers deal directly with end users.

We can help you find the perfect CPAP machine for your needs. Feel free to call or email any time.

Andrew Senske

CPAP-Supply.com is a leading online retailer of CPAP equipment. Located in Spokane, WA CPAP-Supply.com has been serving thousands of customers around the world since 2001. Founded on a belief that patients are their own best primary care providers, CPAP-Supply.com understands the importance of educating patients and customers on both the effects of and treatment for obstructive sleep apnea. For more information visit CPAP-Supply.com or call toll free 1-888-955-2727.