Continuous positive airway pressure without heated humidification causes increased nasal resistance, mouth leak, and worsening airway dryness.1 Up to 75 percent of patients experience these side effects, which often cause them to abandon CPAP therapy.1-4 Environmental factors add further demands to the body's natural humidification process. So travelers headed to extreme climates may experience worsening symptoms and those with seasonal allergies may suffer increased congestion.
CPAP triggers many physiological changes in the respiratory system. Its pressurized airflow can overwhelm the body's natural ability to moisturize the air. When a patient breathes in air that is too cold or too dry, the nose tries to compensate by engorging and secreting mucus to protect its sensitive tissues.
An integrated heated humidifier is the most effective means for overcoming these symptoms. Heated humidifiers support the body's natural humidification process by helping the respiratory system achieve normal temperature and humidity within the over-pressurized air environment.3,5 To be most effective, a heated humidifier must increase absolute humidity with comfortable temperature delivery and control rainout (condensation) in the system.
Absolute humidity is the total amount of water the humidifier delivers per liter of dry air. If a humidifier doesn't provide adequate moisture to the inspired air, patients will continue to experience symptoms like nasal congestion and oropharyngeal dryness. Therefore, total moisture output is the most important consideration in selecting a system.
To support adequate water delivery, the system must transport inspired air at a comfortable warm temperature. Traditional integrated humidification systems add water to the air, but don't sufficiently increase the temperature of the inspired air.
Systems that have a heated circuit (CPAP tubing with integrated heating system) can add additional heat to inspired air while integrated wire systems can give patients more control in adjusting the temperature based on their comfort level. They can increase temperature in the winter for warmer air and decrease it in the summer for cooler air, depending on the severity of their symptoms.
Rainout control is another significant factor in humidification selection. Rainout not only decreases compliance but also leads to dramatic CPAP pressure swings within the system.5 It occurs when too much water is added to the air and the ambient environment is cooler than what the inspired air can support. As a result, condensation occurs inside the tubing. Some systems compensate for rainout control by decreasing the amount of water output from the humidifier. However, this compromises the first component of effective humidity - sufficient water delivery.
Devices with integrated heated wire humidification that also enable intelligent ambient adjustments to heater plates and tube temperatures can provide effective humdification and rainout control. These key components - absolute humidity, comfortable temperature delivery, and condensation control - help ensure patients receive optimal therapy, which aids in increasing overall compliance.
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Mark Rasmus, MD, is medical director of Idaho Sleep Health, Boise, and Jeremy Malecha, BSBME, is senior product manager of ResMed Corp., San Diego.
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