Continuous Positive Airway Pressure (CPAP) therapy is the standard method for treating obstructive sleep apnea. It delivers pressurized air through a mask to keep the user’s airway open during sleep. Many modern CPAP devices include a heated humidifier, which introduces warm moisture to counteract the drying effect of the pressurized flow. The humidifier relies on a water chamber, typically filled with distilled water. If the water supply is depleted, the CPAP continues to deliver air, but without humidity, leading to physical discomfort and potential consequences for the machine.
Physical Consequences of Dry Humidification
The sudden loss of humidification forces the body’s upper airway tissues to compensate for the dry, fast-moving air. This effect is a primary reason why many users find CPAP uncomfortable without a heated humidifier.
Waking with discomfort in the mouth, nose, and throat is the most immediate consequence of the humidifier running dry. The absence of warm moisture causes the mucous membranes to dry out rapidly. This desiccation can result in a sore throat, general irritation, and nasal dryness, which may trigger a sensation of congestion.
The continued flow of dry air can also increase the risk of epistaxis, or nosebleeds, because the delicate nasal lining becomes cracked and irritated. This discomfort often leads to mouth breathing, resulting in a parched mouth and undermining the user’s willingness to continue therapy.
Effects on the CPAP Device
When the water chamber empties, the CPAP device’s heating element, typically a metal plate beneath the chamber, continues to heat. While modern machines are generally designed to prevent catastrophic failure, prolonged heating of an empty chamber is not advisable.
Most current devices employ safety features, such as a thermal cutoff switch or temperature sensor, to prevent the heating element from overheating. If the sensor detects excessive heat, the humidifier function is automatically disabled, often displaying an error message. The machine will likely continue to deliver the necessary air pressure, but the humidifier will cease functioning until the system is reset by adding water and restarting the device.
A significant consequence is the potential for mineral deposition if tap water was used. When the chamber runs dry, residual tap water evaporates, leaving concentrated mineral scale on the heating plate. This residue impairs efficiency and can damage the heating element or the chamber’s plastic material, sometimes causing a distinct, acrid smell.
Immediate Actions and Prevention Strategies
If you wake up to dry air or notice the water chamber is empty, turn off the CPAP machine immediately. Allow the heating plate and chamber to cool completely before handling them. Refill the chamber with distilled water to prevent mineral buildup and ensure the longevity of the heating element.
Prevention Strategies
To prevent the humidifier from running dry, follow these steps:
- Check the water level every night before starting therapy.
- Regularly check the mask seal and replace worn components, as leaks accelerate water loss.
- Adjust the humidity settings to match the ambient environment, especially if the bedroom is cold or dry.
- Use a heated hose, which maintains air temperature and reduces the humidifier’s effort, conserving the water supply.