Reference Articles

OXYGEN THERAPY

Rain-Out in Oxygen Concentrators, What it is, Its Causes and Solutions

Rain-out refers to the condensation that develops and collects in the oxygen tubing when a humidifier is being utilized. It is annoying to the patient because the water eventually makes its way out of the tubing and into the patient's nose. The best way to prevent rain-out is to eliminate the humidifier, but with certain patients and referral sources, that is not always feasible. Since we need to deal with rain-out, let's explore some of the contributing factors.

First, rain-out can occur when the delivery gas temperature is at ambient. For example, even when an oxygen cylinder is being utilized, the occurrence of rain-out can happen as a function of the temperature of the floor. The room may be 70ºF, but the floor could be quite a bit cooler depending on the type of the floor and conditions. Ceramic tile and hardwood floors will be colder than carpeted floors. Floors covering crawl spaces versus basements in the winter months and floors that have air conditioning ducts during summer months are all examples explaining why the floor can be quite a bit cooler than the room temperature. The length of tubing will have an effect as well. Fifty feet of tubing allows the oxygen to come in contact with the cold surface for a longer period of time than 25 feet of tubing. Therefore, the longer the tubing and the colder the floor, the more likely rain-out will occur even if the oxygen delivery temperature is at ambient.

The second main factor contributing to rain-out is when the oxygen is warmer than ambient and travels along the floor. This is the main reason why some concentrators experience more rain-out than other models. Some machines run warmer internally (because of higher power consumption and differences in air flow design) so that the oxygen may be delivered at several degrees above ambient. This allows the oxygen, which is warmer than ambient, to pick up humidity from the bottle and as it travels in the tubing on the floor it begins to cool down giving up the humidity in the form of condensation.

The NewLife has the lowest outlet gas temperature than any other concentrator because it is using less power (only 350 watts) and utilizing an effective cabinet air flow design. If the NewLife is provided adequate ventilation and the back of the machine is spaced eight inches away from the wall, the outlet gas temperature will be within 1ºF of ambient.

The location of a concentrator can have a compounding effect on rain-out. For instance, if a machine is put in a small room (i.e. closet area or storage room) it can raise the temperature of the room. When the oxygen comes out of the concentrator, it will cool down as it travels in the tubing on the floor and thus rain-out. A good example is when a patient puts a machine in a bathroom or a closet and although their house may be 70ºF, the concentrator heats the bathroom or closet up to 80ºF. Additionally, if the concentrator is allowed to run warmer than normal because the intake or exhaust is being partially blocked, or the machine is located where it is pulling in warm air from a heating source, this can also contribute to rain-out.

Following are some other possible causes and corrective actions for rain-out:

• Examine the location of the concentrator making sure the air intake filter is being kept clean, the unit is adequately ventilated at the intake and exhaust, and that there is not a build up of heat coming from the sun or a heating source. Sometimes an afternoon sun baking the concentrator will cause rain-out. Try relocating the concentrator to a shaded, larger and more ventilated area or turn the concentrator 90 degrees to facilitate better circulation.
• If the concentrator is a bottom venting unit and the carpeting is unusually plush, try creating a lower pile surface by using a low pile carpet sample on top of the existing carpeting. Some providers have gotten good results by turning the carpet sample over and running the concentrator on the back side of the carpet sample.
• If the humidifier bottle is over filled it can cause water to spew into the tubing resulting in rain-out. The design of a humidifier bottle can also have an effect. Some providers have gotten better results by going away from the flat-top humidifier bottle to a dome-top bottle, like Salter's. With a flat-top bottle, water droplets can form directly above the outlet port and be pushed into the oxygen tubing. With the dome-top bottle, water droplets are diverted down the sides of the bottle and away from the outlet port.
• Bottles stored in a warm place, cleaned in hot water or even filled with warm water, will all contribute to rain-out. Patients should be instructed to fill the humidifier bottle with room temperature, or better yet, cool water. Some providers recommend to their patients, when using distilled water, store it in the refrigerator   and actually use cold water in the humidifier bottle. Other dealers recommend putting ice cubes in the bottle if they are using tap water.
• Additionally, rain-out can arise when the tubing is cold, i.e., if a dealer brings in tubing from a cold vehicle in the wintertime, as the humidified oxygen come through the tubing, it will rain-out. In the summertime, if a machine is stored in a warm place when delivered, it will create more rain-out.
• The most common way to battle rain-out is with an in-line water trap. This devise is basically a chamber that can accumulate the water preventing it from continuing on to the patient. It should be located in the tubing near the patient for maximum effectiveness.
• Cutting down on the tubing length or elevating the tubing off of cold floor surfaces also gives good results when trying to reduce rain-out.
• One of the biggest problems with rain-out is that once it occurs, it takes a very long time before the oxygen tubing will clear itself. The reason being, the humidified oxygen does not have the ability to hold more moisture and therefore has very little drying effect. One of the best ways of clearing up tubing would be to spill out the water in the bottle and allow dry oxygen to run through the tubing.