CPAP Humidification and Rain Out

Many obstructive sleep apnoea patients using CPAP devices experience nasal congestion and dryness of the nose and throat and this can compromise acceptance of treatment. With the flow of air from a CPAP machine already an irritant, lack of moisture in the air can cause nasal passages to dry and may induce bleeding, swelling, sneezing, snoring and congestion. In these situations the addition of humidification can reduce these problems.

There are two categories of humidification - warm and cold. Cold or "passover" humidification was the first type of humidification therapy for CPAP. Cold pass over is a water chamber that allows air from the CPAP to "pass over" the water before entering the CPAP tube thereby creating humidified air. Although this set up is effective for CPAP users with low pressure settings and those living in a warm climate, it is not optimal as it can become too cold to tolerate and does not provide the most efficient humidification.

A heated humidifier adds moisture and warmth to the air delivered by the CPAP device. Because you can adjust the level of heat, heated humidification offers greater flexibility and reduces more severe symptoms and increases comfort of the treatment by the user. With increased comfort the user is likely to increase compliance and the ability to use the treatment for longer periods.

In the summer months, some are unfortunate to suffer symptoms of hayfever, . A runny streaming nose, often alternating with congestion can be exacerbated by the CPAP treatment. In these cases, heated humidification can also help to relieve nasal irritation and aid continued use of treatment.

One of the problems that can sometimes occur with heated humidification is 'rainout. In cold weather, as the warmed moistened air moves down the hose, it is cooled and can hold less water: as a result it condenses in the tube and mask. This is known as 'rainout which can cause gurgling noises in the tube and water condensation on the face.

There are several ways to help to lessen the problem of 'rainout and the following may help.

  • Always have the device and humidifier positioned lower than the bed

  • Close the bedroom window, turn the humidifier down or raise the temperature in the bedroom at night, to lessen the difference between the room temperature and the hose

  • Tuck the tube under the bedclothes to keep it warm

  • Insulate the hose by covering it with a tubing wrap. Custom made ones can be purchased from ResMed or alternatively you can make your own by wrapping a towel, scarf, bubble wrap or aluminium foil around the tube

ResMed have recently introduced the S9 series. When used with the heated ClimateLine tubing, the H5i gives ideal relief from symptoms even in rooms where the temperature changes overnight - without rainout!

The H5i is incredibly easy to use. Just set your preferred air temperature and the H5i delivers the optimum level of humidification - automatically!

For more information visit or contact the RealSleep team who will be happy to advise you further.