Humidifiers that utilize patients’ exhaled breath offer a solution to dry airways and sinuses when using mini-positive airway pressure machines—albeit with some limitations.

A common issue obstructive sleep apnea (OSA) patients face with traditional CPAP devices is the difficulty of transporting them while traveling, which deters some patients from bringing sleep therapy on their trips and puts their health at risk. Now, travel CPAP devices are proving to be a popular choice as companies create machines that are both lightweight and portable. However, some patients who use these smaller devices say they experience a lack of moisture, waking up with dry mouths and noses—a dilemma that also negatively affects therapy adherence.

Heat and moisture exchangers (HMEs) are a water-free humidification solution, designed to provide moisture for patients who experience a drying out of their airways, while retaining the small size of travel CPAPs. In a 2016 study published in the journal Respiratory Care, researchers found that CPAP adherence was improved when heated humidification was implemented for patients with moderate to severe OSA compared to the group who underwent therapy without it. This improvement in adherence is likely due to the reducing of dry nose and throat symptoms, the authors note.

As the use of travel CPAP devices becomes more frequent, companies are developing HMEs designed to complement them. In 2017, Sleep Review covered the release of ResMed’s AirMini, and while our readers were excited at the prospect of having lighter, smaller machines while traveling, some commented that they turned off their devices because of dryness. “After 2 hours’ use, my mouth, throat, and sinuses were so dry I could barely close my mouth. I turned it off, spending the rest of my night without any therapy,” one commenter wrote. Another said she got up to drink water several times and eventually decided to go back to her traditional device while traveling despite the inconvenience of its larger size.

Since ResMed removed the water tub to shrink the size in order to create the AirMini travel CPAP device, the company sought to find a way to combat the issue of dried out airways and created the HumidX HME. This integrated system captures a patient’s exhaled heat and moisture at the point where the mask meets the tube and stores it within the HME’s tiny paper ridges, according to Laura Jennings, senior manager of retail marketing at ResMed. “When the patient inhales, heat and moisture are released to humidify the air they breathe in for maximum portable comfort, preventing dry mouth and eliminating the need to hunt down distilled water while traveling,” she says.

Jennings adds that the HumidX is designed to provide equivalent levels of humidification compared to a bedside device’s water humidification. That way, she says, the patient enjoys the same level of breathing comfort away from home along with the added convenience of a smaller device that doesn’t require distilled water.

For those patients who still experience uncomfortable symptoms when they use their travel CPAP, even with an HME, it is important to consider the adjustment period. “Just like any new device, there’s an acclimation period,” says Tom Miller, general manager at Breas Medical, the company that makes the Z1 CPAP. “Your sinuses need to acclimate to the change in humidity. [Patients] should definitely try it for a while because it just takes some getting used to.”

Miller says it is also crucial for patients to consider the conditions of their environment when on the go. “If you’re travelling somewhere really dry,” he says, “you can actually ask your hotel if they can provide a humidifier in your room. Having an environment that has enough moisture can really make the difference on top of the benefits of the PAP device.”

Jennings says, “Sources of and solutions for a patient’s discomfort should always be discussed with their physician or home medical equipment provider. ResMed provides two different AirMini humidifiers for varying degrees of humidification. HumidX is recommended as a starting strength, and HumidX Plus can be used for drier climates or when HumidX is not providing adequate humidity.”

For patients looking into HMEs for travel CPAPs who want to be sure they have the right equipment, Miller says the rule of thumb is that the HME be compatible with the mask, rather than focusing on compatibility with the PAP device itself. “Some are integrated into the mask so you can only use [that company’s] HME with their mask,” he says. “We don’t make masks, so we’re agnostic to what mask patients use, and our HME is universal—it works with any mask, but works best if the mask is connected at the elbow, close to the patient’s face. Some have extension tubes that come off the mask, but the problem with those is that you have to put the HME about 8 inches away from the mask which doesn’t work very well. So, in essence, the HMEs are less effective the farther away from the mask you go.”

The same heat and moisture exchanger can be used multiple times by the same patient, but not indefinitely (check with the manufacturer for estimated number of uses). So, what happens when a patient is on the go and is in need of more HMEs? Jennings says many durable medical equipment providers supply accessories, including HMEs. “It is also possible to find an online retailer to purchase them from,” she says. “We would of course advise the patient to check with the provider they are acquiring from as to whether a prescription is needed.”

Although HMEs are a great option for anyone travelling and using a portable CPAP, Miller says patients should start with low expectations, as their travel humidification won’t necessarily measure up to a standard home CPAP device with a water-based heated humidifier. “With an HME, you’re breathing back in the humidity that you exhale, but you’re never going to get it all back,” he says. Either way, the convenience comes with the size. So, Miller says, patients need to consider that benefit when weighing the pros and cons of their travel devices compared to their standard machines.

Miller adds that as much as patients should keep expectations low, companies providing travel CPAPs should also ensure consumers’ expectations are set accurately in the context of full-size CPAP. He says, “A lot of patients fail on travel CPAP because it’s noisier or it doesn’t feel the same. They’re expecting it to feel and sound like their home device. And what we have found is that those [medical equipment] companies that set the right expectation for the patient often have less complaints. Those companies that don’t set the right expectations get more complaints….It will never be your home device because you have a much smaller motor, spinning at a much greater speed, and on top of that, you don’t have a heated humidifier.”

Making devices as compact as possible seems to be a trend in regard to the future of CPAP. Though Miller is skeptical that concerns like excessive noise will be resolved completely, he says to expect the devices to become smaller, and so easier to transport. Making these devices more suitable for travel will surely be an added benefit for patients who want to sleep soundly on their vacation.

Dillon Stickle is associate editor of Sleep Review.