When CPAP humidity is unbalanced, patients can feel as dry as this picture looks.

Photo credit: Dan Gold on Unsplash

One of the top complaints I hear from CPAP users is dryness. While there are many reasons for dryness, not all of them are directly CPAP-related. Considerable confusion potential exists regarding humidifier settings.

The Case

Mr. D presents to the clinic to for an annual follow-up on his obstructive sleep apnea and CPAP therapy. You look at the download from his Respironics machine and notice:

Tube temperature 5

Humidifier 0

One of Mr. D’s loudest concerns is how dry his throat is. A while ago, he turned up the “humidifier” as far as it would go. He doesn’t understand why he is so dry. He now has a cough. His sinuses feel raw and congested when he wakes up. He thinks there is something wrong with his CPAP machine because it isn’t using any water. The tube seems very warm to the touch.

What is the most likely reason for Mr. D’s dry throat? How will you advise him?

Humidifier Function

CPAP machines today usually have parallel features for humidity: the humidifier and the heated tube.

The humidifier includes a water chamber and a heater plate. By applying heat, the humidifier works by liberating liquid water into the air as vapor to help moisturize the nasal and oral passages. If the patient’s nose is dry, bumping the humidifier can help.

Heated tube functionality keeps moisture from collecting in the tube overnight. When too much moisture collects, there is a negative impact on pressure delivery and therapy gets louder. Plus, nobody enjoys getting a face full of water at 2 am.

Some models of machine have an automatic humidifier algorithm, with an option to disjoin them if the patient prefers. Others, as in Mr. D’s case, default to separate settings with tube and humidifier both doing their own thing.

When a heated tube is absent, the only available option will be settings to control the humidity. Without the humidifier connected, there won’t be any active setting options (though the download may still report the software defaulted settings or last settings).

In CPAP therapy, details matter.

As Mr. D’s healthcare provider, if you can spot an issue like this and assist him with fixing it, you will have saved him further delays in frustration. You could refer him to his DME vendor. But how long will he suffer in the meantime waiting for a return call? Assuming someone other than the respiratory therapist answers the phone, will the person on the other end of the line understand the question and have enough experience to help? Will help arrive before the patient gives up because of ongoing discomfort?

Humidifier settings aren’t locked down like pressure settings. These settings are patient accessible with patient comfort in mind.  

Case Answer

Mr. D has his humidifier settings backwards. It will not put out additional moisture while the tube is set to maintain maximum tube dryness. Such a combination of settings parches oronasal mucosa, causing dryness and irritation.

It isn’t difficult to get the tube temp and the humidifier setting backwards.

The Fix

When deciding on starting settings, I try to keep in mind the season of the year and advise middle-of-the-road settings. Unless there is good reason, the default tube temp should be less than the humidifier setting.

In the middle of summer, when ambient air is already hot & humid, it may be best to have the tube temp off and the humidifier down or off. It’s only going to make the air getting to the patient hotter, more humid, and more uncomfortable.

There is a humidity shift in autumn when we close our windows and turn on the heat in our homes. Heat is drying and our patients are likely to need to bump the humidifier a notch or two to compensate for nasal dryness. If the bedroom cools off enough, the tube temp is likely to need a bump to prevent water from collecting in the tube. Once the heat gets turned off and the windows open, the patient can resume summer settings.

Final Thoughts

Humidifier adjustment is a balancing act. A basic understanding of humidifier settings—knowing when to adjust what—can mean the difference between CPAP success and failure.

 Principles of humidifier adjustment for patients and providers:

~Know what is being adjusted and why.

~Always follow your nose. If your nose isn’t dry, the humidity is likely adequate.

~The tube temperature's primary job is to keep water from getting into the tube.   

~To avoid overshooting, adjust one notch at a time.

~Tube temp usually works best when set lower than the humidifier.