Rainout? What is that?

Ever wake in the middle of the night with water pooling in your mask or a popping noise coming from your CPAP tubing? That’s rainout.

Rainout happens when the room’s ambient temperature is significantly less than the humidified air produced by your CPAP machine and the high humidity air begins to condense in your mask and tubing. Warmer air can hold more humidity than cooler air, so as the air cools, water is released and accumulates in the CPAP tube or mask. I had this happen to me several times when I first started using my CPAP, and the noise from the tubing was more frustrating than moisture in my mask.

Below are six tips you can try to prevent rainout and achieve a full-night’s rest:

  1. Purchase a heated tube that keeps the humid air at a consistent temperature from the machine to the mask. Most of the major manufacturers produce a heated tube that is compatible with their machines. They run between $25-$100, and most are specific to a particular model of CPAP. There are a few universal third-party hoses, such as this 3B Medical product, but I have no experience in their efficiency. In fact, I have not used a heated hose to date, but plan to order one when I purchase a new machine in the coming year.
  2. Use a tubing wrap. These are like warm PJs for your CPAP hose. Usually made of microfleece or other insulated material, tubing wraps zip up or slip over your tube, insulating it from the ambient air temperature. Prices vary greatly depending on brands. I bought this one on Amazon for less than $12, and, so far, it works great. I also like it because it quiets the tube as it moves against the bed or night stand. It’s also hand washable. If you have an ACE bandage or two lying around from your basketball or tennis phase, you can use that as well, securing the ends with medical tape. It’s important that the tube is insulated completely from tip to tip for it to work effectively.
  3. Reduce the humidity level of your CPAP. Reducing it by a couple of small increments can help significantly without drying you out.
  4. Place the CPAP below your mattress level and let the condensation drain back into your humidifier. For this to work well, the excess tubing needs to stay above the humidifier at all times so it doesn’t collect in the lowest section of the tube instead of draining into the humidifier. Try to reduce slack as much as you comfortably can.
  5. Increase the temperature in your room by a few degrees. There’s a fine line between a temperature when condensation occurs and when it doesn’t.
  6. Use a Heat Moisture Exchange unit (HME) instead of a traditional water-based humidifier. HMEs are connected between your tubing and the mask and capture warm, exhaled moisture in a sponge-like filter, and they return that warm moisture back into your mask during inhalation. Some compact travel machines, like the ResMed AirMini, use an HME as their primary humidifier with good reviews. This is also a good option for traveling when you need to leave your traditional humidifier at home for weight or space savings.

Rainout is a common and frustrating issue most CPAP users will experience from time to time. Knowing the cause is half of the struggle. Preventing it is the other half. Sometimes, compromising your humidity preference and your preferred room temperature is the key to a full-night’s sleep. – by Matt Lindler (a.k.a. CPAP Matt)

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