Ventilator-Assisted Living©

Spring 2003, Vol. 17, No. 1

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Humidification

Louie Boitano, MS, RRT, Northwest Assistive Breathing Center, Pulmonary Clinic, University of Washington, Seattle

Our lungs are the only internal organs in our bodies that are directly exposed to the outside environment through the air we breathe. Our nasal and sinus passages condition the air we breathe before it reaches the lungs by warming and humidifying the air, keeping the lungs both warm and moist.

Mucus captures the impurities (microscopic particles, bacteria, fungal spores, etc.) in the air we breathe. The mucus and captured impurities are then removed by tiny hair-like structures called cilia that line the airways and act as a conveyor (think mucociliary escalator) to clear the lungs. Breathing dry, cool air for long periods of time can cause the dehydration of mucus that lines the airways of the lungs. Dehydrated, thickened mucus can either slow or stop mucociliary clearance. Thickened mucus then becomes a potential source for lung congestion and infection.

When you have a tracheostomy and breathe through a tracheostomy tube, your natural humidification system is bypassed. Providing adequate humidity to the air you breathe becomes important in maintaining your lung health.

There are different levels of ventilator humidification.

Artifical nose. Use of an artificial nose also called a heat-moisture exchanger, works by holding some of the moisture that is normally lost on exhalation. This consists of a paper wick network enclosed in a plastic housing with open ends that can be connected to a home ventilator breathing circuit between the tracheostomy tube and the exhalation valve. The paper wick captures moisture on exhalation and provides moisture with inhalation. Hudson RCI, Portex and Boston Medical are among several companies that manufacture artificial noses.

Pass-over humidification. A water chamber, also called a pass-over humidifier, is in the circuit without heat. This provides a subtle amount of moisture. An example is the LX Pass-over Humidifier (Respironics Inc., www.respironics.com). Pass-over humidifiers are primarily used for non-invasive mask ventilation or CPAP therapy (the ConchaTherm 2000 from Hudson RCI), but do not provide enough moisture for ventilation through a tracheostomy.

Heated water chamber with temperature adjustable up to 39°C. Water droplets are likely to appear in the ventilator circuit but are not dangerous if the circuit contains a water trap and the circuit is monitored on a regular basis. Examples are the HumidAire™ (ResMed) and the MR410 humidification system (Fisher & Paykel Healthcare Corporation).

Photo of Fisher & Paykel's HC500Heated water chamber with heated wire in hose at the same temperature. The heated wire breathing circuit supports both uniform heat and humidity (beneficial for cooler climates). Water droplet buildup in the hose is less likely to be a problem. An example is the HC500 humidification System (Fisher & Paykel Healthcare Corporation). Not all insurance carriers will reimburse for this type of humidification system.

A heated humidifier in the ventilator breathing circuit warms the air and provides enough moisture to prevent mucus dehydration.

A common problem encountered with heated humidification is condensation or "rain out" — when warmed humidified air cools as it travels through the breathing circuit surrounded by cooler air.

This condensed moisture must be removed before it either restricts the flow of air through the breathing circuit or causes choking by entering the tracheostomy tube. A water trap can be placed at the lowest point in the breathing circuit to collect the condensation.

The heated humidifier must be set at a temperature high enough (30-34°C) to provide adequate humidity after a portion of the water vapor is lost to condensation in the breathing circuit. The circuit can be insulated to decrease the amount of water lost to condensation, but this can be bulky and impractical.

Heated wire breathing circuits generally require significantly more support because they are non-disposable and must be cleaned regularly. The more common disposable breathing circuits with water traps are more convenient to replace, but require regular monitoring for water accumulation and emptying of the water trap in the breathing circuit.


Treating Bronchitis with H2O

Jerry Daniel (JerryPD2000@aol.com)

In 2000 I marked 45 years of successful positive pressure ventilation by tracheostomy, but there was a dark cloud hanging over my head. My chronic bronchitis was getting worse, and prednisone and antibiotic Cipro treatments were becoming more frequent but less effective. My frogbreathing-powered cough was not working, and my bronchial tree seemed tough and dry. I had frequent hospitalizations and even considered moving from the state of Washington back to Southern California for a more favorable climate.

My pulmonologist and respiratory therapists in the hospital tried to make me comfortable with the Cascade humidifier, but I resisted it. Then they brought in the Fisher & Paykel HC500 heated hose humidifier. I was more receptive because it looked compatible with my LP10 ventilator. I have now used the HC500 all night and intermittently during the day for three years. The humidifier is always inline with the LP10. The secretions are under control; I switch the heating elements off and on as needed. Tracheal suctioning did not seem to work before, but now it works well. I have not needed prednisone treatments, antibiotics, or to be hospitalized, and the humidifier is easy to maintain at home.

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