Positive air pressure therapy, or PAP therapy, is used to treat obstructive sleep apnea (OSA) or central sleep apnea (CSA), conditions that cause temporary loss of breath during sleep due to airflow restrictions in breathing passages. PAP therapy comes in several forms; the most common types are continuous positive air pressure (CPAP), bi-level positive air pressure (BiPAP), and automatic positive air pressure (APAP). All PAP therapy types feature an airflow generator (known as the PAP machine) that draws in outside air using an electric fan, humidifies and pressurizes the air, and then delivers it to sleepers through a connective hose and a nasal or full face mask.
Virtually all CPAP, BiPAP, and APAP machines sold today can be powered with AC voltage. Most machines can also be powered with DC voltage when owners are traveling, either with built-in DC outlets or by using inverters. This allows the machines to run off external battery power, although some are equipped with backup batteries in case of unexpected outages. Prices vary for these products. External batteries for PAP machines generally cost $75 to $500, depending on the battery type, while inverters are typically sold for less than $100.
This guide will examine power options for PAP machines, provide some tips for overseas travel and product troubleshooting, and share some considerations for first-time buyers.
CPAP, BiPAP, and APAP machines need power to operate. Most nightly users rely on AC voltage, and operate their machine using power cords plugged into wall outlets. AC outlets in North America produce 110 volts, but the voltage output number varies in other parts of the world (see next section).
However, AC voltage may not be readily available — particularly for PAP users who are traveling. A recent survey found that more than three-quarters of people that rely on PAP therapy bring their machine when they are on the road. DC battery voltage is a potential alternative for PAP machines in these instances. Users can operate their machine using DC power in one or more of the following ways:
- An inverter, which changes DC voltage into AC voltage.
- A DC power cord, which connects to 12-volt outlets; most of these cords are designed to connect with cigarette lighter outlets.
It’s important to note that an inverter is not needed for machines that are compatible with DC power cords. However, virtually all PAP machines sold today can be operated with inverters. To determine whether an inverter is required, check the machine specifications for verbiage related to a ‘DC outlet.’ If specifications are not available, check the machine itself; the outlet is normally located on the back or side.
It’s worth noting that very few PAP users rely on battery power. According to survey results, roughly 10% of PAP users have ever utilized battery power to operate their machine; the vast majority of respondents who have used a battery did so for travel-related purposes.
When determining battery selection, it’s important to consider the PAP machine’s pressure settings. The airflow delivery of PAP machines is measured in centimeters of water, or cmH20. A standard PAP machine will deliver an airflow range of 4 cmH20 to 20 cmH20. The higher the setting, the more power that will be needed to operate the machine. CPAP machines deliver airflow at a fixed (or continuous) pressure rate throughout the night, while BiPAP and APAP machines toggle between two or more pressure settings based on the sleeper’s breathing patterns. Most PAP users receive at least 10 cmH20 of airflow at any given time.
Due to the power requirements for higher pressure settings, robust batteries are often needed to power a PAP machine throughout the night. These machines require a fair amount of power, Power needs may be magnified by using an inverter and/or a heated humidifier, which both tend to use up a large amount of battery life. The following battery options tend to work best when powering PAP machines:
Deep-cycle marine battery: Deep-cycle batteries expend a small amount of energy over a longer period of time. While performance varies by model, most deep-cycle marine batteries will power a PAP machine for at least two consecutive nights (depending on the pressure setting) before recharging is needed. In order to use a deep-cycle marine battery with a PAP machine, a DC adapter cable is needed; this attachment connects to the cigarette lighter attachment of the DC cable, and features alligator clips (like those found on jumper cables) that connect directly to the battery.
It’s important to note the difference between deep-cycle marine batteries and starting marine batteries, which expend larger amounts of energy over shorter periods of time. Additionally, dual-purpose marine batteries are designed to serve both functions; however, these batteries typically do not match deep-cycle or starting batteries in terms of duration or energy output, respectively. Because PAP therapy requires several hours of power, deep-cycle marine batteries are considered superior to starting and dual-purpose marine batteries for powering PAP machines.
Battery packs: A PAP machine can also be connected to lithium ion battery packs using the DC cable adapter described above. Battery packs are lighter and more portable than deep-cycle marine batteries, but most need to be recharged every one to two nights (depending on the pressure settings). Also, please note that most battery packs sold today are only compatible with a limited selection of PAP machines — or only one model, in some cases.
Backup battery: A small number of PAP machines sold today come with built-in batteries that will power the machine when other sources are unavailable. If a PAP machine does not come with an integrated battery, then a battery pack may serve this function.
The table below illustrates some of the main differences between these three battery options:
||Expected Battery Life
|Deep-cycle marine battery
||An external battery that expends low amounts of energy over prolonged periods
||16 to 24 hours (2 to 3 nights)
Depends on pressure setting
|Longer-than-average battery life
Compatible with all machines using DC cable adapter
|Bulky and heavy for travel
Charge levels may not be displayed
|$75 to $150
||An external battery that expends a moderate amount of energy over prolonged periods
||8 to 16 hours (1 to 2 nights)
Depends on pressure setting
|Lighter and more portable than deep-cycle marine batteries
Charge levels often displayed
|Shorter life compared to deep-cycle marine batteries
Most models not universally compatible
|$250 to $500
||A built-in battery that kicks in when power outages occur
||8 hours or more, depending on model
Somewhat depends on pressure setting
|No external components
Less affected by pressure settings than other battery options
|Very limited availability
PAP machine purchase required
|$400+ (including PAP machine)
While AC outlets in North America put out a current of 110 volts, this number increases to 220 or 240 volts in most other places worldwide. For this reason, an adapter plug (also known as a power converter) should be used to connect the PAP machine’s AC cord to a wall outlet in these places. Not doing so can cause the machine to malfunction.
Additionally, PAP users should exercise the following precautions before traveling to international destinations:
When shopping for a new battery and/or inverter for a PAP machine, here are a few key variables to take into account: