Condensation takes place for one primary reason: air is cooled to a point at which it can no longer hold water. When the air is cooled to this point, water vapor turns to liquid water. In the sky, this is how clouds are formed; the water vapor turn to liquid water droplets that stick to particles in the atmosphere. In your CPAP tube, rainout occurs in a similar fashion.
If a heated humidifier is being used, then the air temperature may be slightly warmer inside the CPAP tube. Probably not noticeably warmer, but just slightly. The warmer air can hold a bit more moisture which means less visible water in your tube. The idea behind tubing wrap, then, is that the insulation helps keeps the inside of the tube slightly warmer than the temperature just outside the tube wall.
So, why, you may ask, does covering the CPAP tube with an insulating sleeve reduce rainout? That's a good question, because it seems as though covering an inanimate object that isn't producing heat - or that isn't producing much heat - would have no effect on the temperature of the air in the CPAP tube or on the temperature of the CPAP tubing itself. Let's take a look, though, at a common cause of condensation that occurs quite freqently at the dinner table to see how rainout might be prevented.
When you fill a glass full of ice water and set it on a table for a few minutes you'll see that condensation forms on the outside of the glass. This takes place because the air near the ouside of the glass becomes very cold - so cold it can't hold any more water. As a result, visible water droplets form on the outside of the glass.
Now, imagine your bedroom is the glass of ice water. It is common during the night for the temperature in homes to drop. When you go to bed, you may turn the thermostat from 69 to 67. That temperature decrease will occur over the course of a couple of hours. As your room gets colder it is acting like that glass of ice water. Air that comes in contact with a CPAP tube that is cooling down will tend to condense. If the tube is wrapped with an insulating sleeve, though, the temperature of the tube wall won't change very quickly (i.e. it won't change nearly as quickly as the room temperature might change).
Another issue to consider when discussing rainout is the positioning of your CPAP tube. Many CPAP users position their CPAP machines and tubing in such a way that a p-trap is created in the tube. For example, the tube might drop below the level of the CPAP machine and humidifier and then rise up to your face, creating a low point where water will gather. If this is the case, then water vapor that has condensed in the tube will accumulate in the p-trap. Subsequently, the accumulated water will be blown out through the mask and onto your face. Even if you aren't able to completely prevent condensation in your CPAP tube, you can try to position your tubing so that condensation will tend to drip back into your humidifier water chamber, rather than accumulate in a puddle and then end up on your face.
We recommend using CPAP tubing wrap even if you don't use a CPAP humidifier if you're interested in protecting your CPAP tubing from being damaged (i.e. ripped, torn, eaten by the cat, etc.), or if you'd like to add a little color to your CPAP setup or make it look a little less clinical. The ResMed CPAP tubing wrap is the easiest to install with a full length zipper, and it's the most effective insulation we've seen. It's just one example of the many sleep apnea supplies we sell to make your therapy more tolerable and effective. Give it a try, and tell us what you think!
CPAP-Supply.com is a leading online retailer of CPAP equipment / sleep apnea supplies. 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."