Despite extensive patient education efforts on the part of many HME providers, nasal CPAP is known to be associated with a high prevalence of nasal symptoms that subsequently limit patient compliance. The nasal discomfort is generally due to the drying effect of the high airflow delivered by the CPAP machine.

One would think that a simple answer would be to add a humidifier. Several factors limit the ability of humidity alone to solve the problems. Nevertheless, humidification can help increase patient comfort and change patient perceptions about nasal CPAP.

Complaints associated with CPAP are generally associated with the upper airway. After all, the nasal cavity is the gateway to the respiratory system. Dry air used with CPAP that is not adequately humidified may lead to such patient complaints as nasal/oral dryness, nasal congestion, rhinorrhea, sneezing, or epistaxis. Nasal symptoms are believed to be experienced by 30% to 70% of patients using CPAP.

Mouth leaks are thought to be associated with upper airway symptoms. The increased nasal resistance caused by the drying effect of the air delivered to the CPAP unit is a contributing factor leading to oral leaks. Mouth leaks produce high unidirectional airflow over the nasal and oral mucosa. The airflow increases a patient’s mouth and nose dryness and nasal congestion. If a heated humidifier alone is unable to eliminate oral leaks and upper airway discomfort, then a full-face mask is often employed.

The full-face mask has been shown to be the best choice to reduce problems associated with oral leaks and/or contributing to nasal discomfort. Unfortunately, a large percentage of individuals who attempt to use a full-face mask are unable to tolerate the mask. Much of the patient discomfort is caused from the mask being improperly applied. When a patient is effectively educated and the mask is fit properly and used with a headgear designed specifically for it, full-face masks are very effective and often tolerated well.

Patient-perceived benefits from CPAP are the most important factor for successful CPAP therapy; however, with the incidence of nasal discomfort associated with the drying effect of CPAP approaching 70%, CPAP compliance and the perceived benefits are sorely limited.

Heated humidifiers are the best choice to increase comfort, reduce nasal symptoms, and increase compliance. Unfortunately, in the age of cost-effectiveness and cost cutting, many insurance companies are unwilling to pay the high cost of heated humidifiers, even when research studies clearly demonstrate the benefit of heated humidification for use with nasal CPAP. Heated humidifiers can cost up to five times more than cold passover humidifiers. Cold passover, although much less expensive, often does not add enough humidity to increase patient compliance. It may benefit individuals without adverse nasal symptoms, but are of little help for those suffering CPAP-related upper airway discomfort. The need for heated humidifiers can be justified by demonstrating the high percentage of nasal discomfort, morphological changes to the airway, and poor patient compliance without it.

Financially speaking, there are few reasons why an HME provider would not prefer to use a heated humidifier. Aside from providing better patient comfort and increased compliance, heated humidifiers are typically reimbursed at significantly higher rates than cool humidification ($300+ vs $100; E0562 vs E0561). Heated humidifiers are typically billed as a purchase, while CPAPs are rentals. The return on investment for a heated humidifier can be quicker for a dealer to recoup than a 15-month capped rental for a CPAP.

Granted, there are still payors that require patients to “fail” on cool passover before paying for a heated humidifier, but the broader market is shifting toward providing patients with heated humidifiers at setup giving them the best opportunity to succeed with their CPAP treatment up front.

Although often helpful, humidifying CPAP can complicate the therapy, adding further responsibilities for the patient. The humidifiers must be properly cleaned and filled on a regular basis. If a humidifier is not cleaned properly, there is a risk of colonization and possible infection of the patient.

Heated humidification also increases the potential for water accumulation within the CPAP tubing. Delivering too much humidification can create “rainout,” which can occur when a heated saturated gas cools down in the CPAP tubing. Gases at higher temperatures can hold more moisture than cooler gases. However, when you take a saturated gas and cool it off, the moisture has to go somewhere; often it “rains out” in the tubing, causing a pool of water to form. This water creates resistance to the airflow in the tubing and can cause deviations in the set pressure.

This rainout phenomenon occurs most often when patients try to get high levels of humidity and sleep in a cold room, or with the windows open. This causes the room temperature to drop and the tubing cools down and starts developing rainout.

Providers can carry technology that automatically compensates for changes in flow and room temperature. This largely prevents rainout from developing in the tube, and provides additional humidity to the patient when faced with increased flow (leaks) so that the patient does not become dry.

The CPAP device should be compact and easy for patients to operate. The humidifier should be integrated with the CPAP device to minimize the number of pieces that a patient needs to carry and manage (such as two electrical cords or a humidifier that does not fit in a CPAP carrying case).

Above and beyond simple ergonomics, providers should ensure that the humidifier actually provides clinically significant levels of humidity. There seems to be a trend developing in the marketplace to move toward smaller humidifiers. However, when you lower the capacity of a humidifier chamber, you are more than likely compromising the level of humidity delivered to the patient. Delivering lower levels of humidity is likely to result in an increase in the side effects that would have been minimized by using a heated humidifier.

If the chamber is smaller, the manufacturer should ensure that the water does not run out during the night. The easiest way to manage this is to lower the heater plate temperature to ensure that less water leaves the chamber, and thus less humidity is delivered to the patient. Some humidifiers coming onto the market deliver as much as 40% less moisture to the air than that which has been clinically proven to minimize nasal airway resistance. One humidifier coming to market will likely deliver even lower levels of humidity, as the chamber capacity is down to 275 mL vs a typical 400 mL chamber.

Taken as a whole, the current research supports the benefit of humidity when added to CPAP. When the addition of heated humidity alone does not eliminate problems associated with CPAP use, then a full-face mask is an excellent option. Heated humidification along with a full-face mask may completely eliminate water loss in the airway when CPAP is used. Humidity is essential for a healthy airway, and when CPAP is used without added humidity, the health of the airway is clearly in jeopardy for a majority of CPAP users.

Megan Rauch, RRT, is a respiratory care practitioner and sleep specialist at Mott Children’s Hospital and the General Research Center at the University of Michigan Medical Center, Ann Arbor.