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Cleaning CPAP Equipment

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Few topics engender more diversity of approach than that of routine cleaning of CPAP equipment: humidifier chambers, tubing and masks. (I might dare also include the checking and periodic replacement of machine filters.)

Practices range from doing nothing (often accompanied by the claim that “…. and I’ve never been sick or had any problem”) to vigorous daily disassembly and thorough washing (often accompanied by the conclusion that therefore “…. I’ve never been sick or had any problem”).

Philosophies range from “people today would be a lot healthier if they ate more dirt” (which might or might not be so, but “back in the day” life expectancy surely was a lot shorter) to germophobic fatalism, to holistic health practices including homeopathy and nasal irrigation (reminds me of reading literature on the virtues of daily enemas).

The equipment manufacturers don’t help much. Almost all advise daily draining, washing, and rinsing of humidifier chambers and masks. (Perhaps because tubing isn’t often sold as a “branded” product, there is less emphasis on daily care in that realm.) They are often accused of taking that position as a litigation preventive measure; that may or may not be so. They rarely present actual research to support or explain their cleaning recommendations.

Recognizing that my complete objectivity and rationality is not infrequently called into question (even, or perhaps especially, by those who know me best), let’s take a stab at thinking through the issues. In that way, whatever decision we reach, we can pretend that it’s based on careful and deliberate thought, rather than on our own laziness or on our obsessive-compulsive inclinations.

General Principles

● Microbes tend to grow in warm, moist, dark places.

● Our world, including the air we breathe, is full of microbes.

● The danger posed by commonly encountered microbes is directly proportional to the number of them that get inside us, and inversely proportional to our overall state of health. (This is true also of microbes normally found in our own bodies. Change the number or ratio of our internal microbial flora, or experience a general decline in health, and our own microbes can literally “eat us alive”.)

Based on these principles, let’s consider the equipment in our CPAP set-ups, in order from the most distant components to those closest to our bodies.

Air Filters

ResMed suggests, “Inspect the air filter every month to check if it is blocked by dirt or contains holes. With normal use of an S8 AutoSet II, the air filter needs to be replaced every six months (or more often if your device is in a dusty environment).”

Respironics states, “Under normal usage, you should clean the gray foam filter at least once every two weeks and replace it with a new one every six months. The white ultra-fine filter is disposable and should be replaced after 30 nights of use or sooner if it appears dirty. DO NOT clean the ultra-fine filter.”

Why does Respironics suggest so much more frequent checking and changing of filters? One explanation is that their filtering system is much more efficient than the open fiber filters – reminiscent of inexpensive filters used in my home HVAC system – employed by ResMed. Fine particulates appear much more likely to be blocked and kept out of the air stream – and thus much more likely to foul and block the filters – in the Respironics systems. Still, it does not necessarily follow that the presumed higher efficiency of the Respironics filtration is either necessary or helpful – do we need to breathe air that is cleaner than our room air?

Respironics nicely summarizes why filter cleaning is important:

Caution: Operating the device with a dirty filter may keep the system from working properly and may damage the device. …

Caution: Dirty inlet filters may cause high operating temperatures that may affect device performance. Regularly examine the inlet filters as needed for integrity and cleanliness.

Ah, a reference to “cleanliness.” Comfortable, culturally correct, but still, just a bit …. vague.

CPAP Machine

No one recommends that we clean the CPAP machine (at least not beyond the careful application of a moist cloth to the exterior to remove grease, grime and dust). Isn’t that an oddly fortunate coincidence, since there’s no safe way in which we’re ABLE to clean the belly of the beast. Besides, though it may be dark inside and warm when it’s running, it’s dry, and nothing goes through it except filtered room air.

Well, that may not be quite exactly true. There are two ways in which moisture might get inside. The most serious is if there’s backflow into the machine from the humidifier. This, apparently, is most likely to happen if the set-up is moved while the machine is attached to a humidifier containing water. BIG OOPS. Not only is there danger of microbial growth wherever the water manages to ooze, but there is also danger of electrical component malfunction, corrosion, or even potential short-circuit and fire. The manufacturers are unanimous:

ResMed: “Water must be prevented from entering your flow generator. Do not transport the flow generator with the H4i attached.” …. “This Limited Warranty does not cover: …. d) any damage caused by water being spilled on or into a flow generator.”

Respironics: “If the device and humidifier fall and water gets into the device, drain all water out of the device and make sure it is completely dry before reapplying power. … If the device falls or water gets into the device upon falling, let the device dry completely and then restart it. If it does not operate correctly after falling, contact Respironics or an authorized service center.”

But there is a second, more subtly insidious, and perhaps more common way for moisture to enter the CPAP machine and cause any or all of the nasties described above. That is by diffusion. The physics is very simple and straightforward. Just as “nature abhors a vacuum,” nature abhors any difference in concentration of any substance.

You are using your CPAP with a heated humidifier. The CPAP blows air in one direction: away from the machine, over the water surface in the humidifier chamber, and towards you. You sleep well, with not a care in the world. In the morning, you wake up, turn everything off, and go about your business. (Or, similarly, you get up during the night for an extended period.) And diffusion goes about its business.

Water has a high “specific heat” – higher than almost any other common substance. That means that it takes more heat to raise the temperature of water, than it does to raise the temperature of an equal mass of any other substance, an equal amount. That also means that warm water stays warmer, longer than just about anything else. And THAT means that the moisture level – the absolute humidity – the concentration of water – in the air above the water in the humidifier chamber, will be greater than that in the air anywhere else in the room. That water vapor will want to get – everywhere, anywhere else.

If tubing is connected to the humidifier chamber under these conditions, that humid air will begin to diffuse into the tubing. And in both directions: since no air is flowing, it will equally seek to go into your main tubing, AND into your CPAP machine. In either direction, that warm, moist air will find cooler surfaces. And on cooler surfaces, water will precipitate out of the air. (Yes, right, just like rainout!) The amounts may be minute. Or not. Diffusion occurs on a molecular level, and the warm water vapor can find its way through the most minute cracks and crevices. Even into areas of the machine where little airflow moves – so that there may not be the “normal” opportunity for drying during normal machine use. Dangers of machine damage due to this water vapor diffusion are arguably small. Dangers of providing a habitat for microbial growth may also be arguably small.

Still, it’s simple enough, with most machine designs, to disconnect the direct connection between the humidifier and anything else. With a stand-alone humidifier, disconnect the tubes. With a ResMed Humidaire humidifier, lift the top cover to unseat the gasket and let the humid air pass harmlessly into the room. With Respironics humidifiers – sorry, I have never used an integrated Respironics humidifier, so I don’t know how best to take action. (By the way, if you use a Fisher & Paykel stand-alone humidifier with the HC-325 chamber, the blue plastic caps that come with each new chamber should be kept - they make an excellent cover for the chamber AFTER you remove the tubing. And an excellent cover for the CPAP machine blower port.)

This is a simple, proactive way to prevent even the small possibility of physical damage, and, more to the point of this article, to prevent even the small possibility of microbial growth inside the blower.

Aha! ResMed has already thought of this, though paradoxically they give what for all the world looks like a bogus reason for their very innovative response. In their manual for the HumidAire series of humidifiers (though generally NOT in the manuals for their CPAP machines themselves) they write:

“Note: In order to assist the heater plate in cooling, some flow generators continue to blow air gently for up to an hour after treatment has stopped. However, you can unplug the device from the power outlet at any time and allow the heater plate to cool without airflow. ”

In fact, with water still present in the chamber, this slight blowing will have virtually no effect on the humidifier heater plate temperature. Their comment that this function can be easily aborted strongly suggests that there is no need to cool the heater plate. (The best way to cool the heater plate is to remove the reservoir chamber!) Nor is this function useful, as some have suggested, in drying the hose. To the contrary, it is still warm, moist air being gently blown INTO the hose, and rainout may result.

What this "gentle blowing" DOES accomplish is to keep warm moist air flowing AWAY from the machine, preventing diffusion of water vapor INTO the machine. Well done (though poorly explained), ResMed! But even better is to simply disconnect or remove the humidifier chamber from its connection to the blower.

Machine–to–Humidifier Hose

This component exists principally in systems which utilize a “stand-alone” rather than an integrated humidifier (though even with an integrated system, “something” connects the machine to the humidifier). Such a hose, if it exists, should be inspected periodically for physical integrity and leaks (run you hand along and around it while the machine is running to check for any airflow), and inspected visually for anything inside that should not be inside. The need for any active cleaning should be rare.

How to dry CPAP Hoses

Humidifier Chamber

Now the disputation begins in earnest. The “never empty or clean unless there’s an obvious reason to do so” advocates make some excellent points:

● even if the occasional microbe gets into the chamber, if you are using distilled water (as you probably should be), there’s nothing for them to feed and grow on.

● even if there is microbial growth in the water, there little likelihood that they can enter the airstream, and

● even if microbes did enter the airstream, there is little evidence that they could successfully navigate and survive the trip down the main tubing in sufficient number to cause illness.

On the other side of the table, activists may well claim:

● distilled water is not necessarily sterile water, and even if it were, it can no longer be considered sterile once the bottle has been opened

● even with filtration, air flowing through the system is neither microbe-free nor particulate free, and particulates (which may provide microbial nourishment) certainly have an opportunity to enter the humidifier during the filling process, and (depending on whether and how portals are covered) during the day.

● while it is true that humidifiers work by producing molecular water which “dissolves” in the overlying air, rather than water “particles” which can “carry” microbes “piggyback” down the tubing, there are other potential transport processes. Observation of the surface of CPAP humidifiers during respiration generally show “rippling” as airflow increases on inspiration. This non-laminar flow “rippling” is effectively wave generation with associated “spray” production – i.e., water particulates capable of carrying microbes. Convection within in the heated water will regularly carry microbes, if present within the water, to the surface, waiting for their “ride”.

● in addition to the presence of surface-effect “spray” water particulates as just described, “clumps” of microbes, even without water droplets as a transport vehicle, can be “lifted up” directly by the non-laminar airflow, either from the water surface, or from the humidifier chamber walls as the water level falls through the night.

There is little good, hard, convincing, available science upon which to base a firm preference for either of these two positions. A published study of radioisotopes placed in humidifier water was found to detect radiation as have traversed the tubing, but only at very high pressure (and correspondingly high flow-rate, due to increased venting flow at higher pressures) conditions.

In a brief departure from focusing on microbes, a mention of mineral precipitation is in order. In all but distilled water, there will be dissolved mineral ions. As molecular water is lost overnight through evaporation (whether in a heated or even in a passive pass-over system), the mineral concentration will increase. (It should be noted that periodically adding additional fresh water through the night will help to minimize this.) There may come a point when the minerals reach their saturation point, and begin to precipitate out of solution, potentially resulting in a build-up on the chamber walls and, more likely, on the heating plate. There are two principal down-sides to the deposition of mineral precipitates. First, they tend to form cavernous networks, which provide attractive housing for microbes. (So I lied; we are still talking about microbes.) Second, precipitation on the heater plate tends to decrease the efficiency of heat transfer. (That it may look unattractive is a personal problem; deal with it.) The general recommendation for removing such precipitate is rinsing in a dilute vinegar solution, with the acidic environment hopefully dissolving the minerals and allowing them to be rinsed away. (In addition it is claimed that the vinegar has mild antiseptic properties, helping to kill, yes, again, microbes.) It should also be noted that many insurance plans cover twice-yearly humidifier chamber replacement.

Thus, the range of options for humidifier chamber care and maintenance, from least interventionist to most conservative, runs something like:

● doing nothing; simply adding water each night
● draining out the leftover water and allowing to dry, each morning, or periodically
● draining, rinsing and allowing to dry, each morning, or periodically
● all the above, plus use of soap and/or vinegar, followed by thorough rinsing

A final comment on drying. If you are “drying out” the humidifier at all, the faster the drying process, the less likely that any microbes will find residual moisture and “settle in.” (The bathroom, by the way, may be the most convenient place for drying, but it is the least desirable, in view of typically higher moisture levels, typically higher levels of airborne particulates, and – yes – typically higher level of airborne microbes.) Drying can be accelerated by vigorous shaking, not only to remove excess water, but also to break up remaining water into smaller droplets. (Smaller droplets have a larger surface-area to volume ratio, and will therefore evaporate more rapidly.) Inserting a clean, thin, threadbare washcloth into the chamber prior to the shaking process will facilitate the removal of excess water. And blowing air through the chamber with a CPAP machine will greatly enhance the evaporation of any remaining water.

Where you choose to place yourself on this spectrum is largely a matter of choice, involving such factors as your overall health, your overall “tidiness”, and your overall risk tolerance preferences. It’s hard to imagine even the most “non-interventionist” CPAP user ignoring a humidifier chamber which begins to look cruddy or colorful. If a decision regarding action is based on what you see (or more precisely, on what you NOTICE), then we in fact are already operating on an analog basis – how much contamination is present – rather than on a yes/no digital basis - whether or not contamination is present. Even in our digital age, much of life remains analog.

Main Tubing: Humidifier to Mask

People often talk about cleaning their tubing, but few seem to do anything about it. I suspect that’s because the process is so cumbersome. And perhaps also because, arguably, it’s relatively unnecessary.

In the absence of rainout (precipitation of water from warm, moist air against the cooler walls of the tubing), the tubing interior typically remains dry. Mask venting and continuous airflow from the machine (and, for some masks, extension tubing) typically prevent any significant amounts of exhaled air from retrograde entry into the tubing. Under these “ideal” conditions, there’s nothing needing to be cleaned.

Unfortunately, conditions are sometimes less than ideal. (Descriptions on the CPAPTalk discussion forums of insects entering the tubing will be left for those interested to find on their own.)

It is a good practice to INSPECT your tubing on a regular basis. When turning the machine on at night, run your hand along the length of the tubing, feeling for leaks. In the morning, visually check the entire length of tubing. Look for evidence of water droplets or mist suggesting rainout; look for any dark or discolored areas or objects. Tubing which is transparent is obviously highly preferable to tubing which is more or less opaque in this regard. Tubing which is covered (to prevent or diminish rainout) should periodically be “undressed” so that it can be inspected.

If there has been ANY rainout, you now have a condition in your tubing which will arguably support microbial growth. (See the discussion about humidifier chambers, and the variety of opinions about whether microbes can in fact get into, and live in, the tubing. I will simply suggest that the longer you go without inspecting, drying or cleaning your tubing, the greater the possibility of microbial growth, survival, and migration down your tubing toward you face, becomes.)

If there has been rainout, it should be PROMPTLY and RAPIDLY dried. The hose should be first shaken, from the center toward each end, to remove as much water as possible. If you have sufficient room, twirling the hose, from the center toward each end, will also expel excess water. The most convenient technique for rapid drying is to run air from your CPAP blower through the tubing until all evidence of water is gone. (Some machines may automatically shut off when no resistance to flow is encountered. On some of these, it may be possible to disable and turn off that feature. It may also be possible to put a flow-limiting connector on the end of the tubing, but this will increase drying time, since maximal flow will product the most rapid evaporation.) Sucking air through the tubing (rather than blowing as with a CPAP machine) may be attempted; devising a connector to the suction of a household vacuum cleaner has been suggested. Another attractive suggestion (presented on the CPAPTalk forum) is that of connecting a weight to one end of a six-foot-plus length of fishing line, and connecting a thin, dry cloth to the other end of the fishing line. Drop the weight into one end of the tubing, let it pull the line through the tubing, and then the fishing line can be used to pull the dry cloth through the tubing. Special care may need to be taken with heated tubing, or with tubing having custom connectors on one or both ends.

All else failing, tubing can simply be left hung to dry, but passive diffusion of air through a narrow six-foot tubing is not an ideal methodology. Under such circumstances, it has been wisely recommended that one have a spare second tube to use while the first one is drying overnight. For additional ideas on how to dry the tube see the section here on CPAP FAQs

Actually “cleaning” the tubing may occasionally be desirable, as for example when rainout droplets have been allowed to sit in the tubing for days, or even just hours. Some people "dunk" the tubing into a basin of soapy water; possibly a bit awkward due to the tubing length. Simply rinsing the interior by holding one end against a spigot, and allowing the other end to drain into the bathtub, may be sufficient. (Some people have described taking the tubing into the shower with them for rinsing!) If it is desired to use soap (or some other safe cleaning material), the use of a male-to-male adaptor makes the task much easier. (A male-to-male adaptor is typically a small plastic connector, both of whose ends will fit inside the rubber cuffs at the ends of the tubing, and which may be used to connect two hoses together. Some masks come with parts which may be usable for this purpose – e.g. the swivel assembly on a Mirage Activa. An adapter suitable for such use is sold by CPAP dot com at: http://www.cpap.com/productpage/hose-coupling-swivel-adapter-cpap.html .) After partially filling the hose with water, and adding a suitable amount of soap, use the adapter to connect the two ends so that the tubing forms a continuous loop. The cleaning solution can now be easily “swished” through the tubing, and allowed to stay inside for as long as is desired. After cleaning, rinse thoroughly and dry rapidly, as already described.


While the risk of microbes reaching us through the airstream is debatable, the risk of contamination of the mask is far less controversial. All night, every night, we are exhaling warm (at body temperature) moist (100% relative humidity) air, laden with microbes (yes, our own) from our upper airway, and proteins and enzymes and sloughed cellular debris, into the mask. The thought question with regard to mask cleaning is not so much, “Do you feel lucky?” as, “Why do you brush your teeth?” The conditions which can lead to halitosis, gingivitis, dental decay, and that grubby trench-mouth feeling, is now present on and in the surfaces and crevices of our masks. Further, he grease and grime on our facial skin is transferred to the cushions.

Despite the difficulty of making a convincing case AGAINST regular mask cleaning, CPAPTalk forum postings demonstrate a wide variety of practices (and a wide spectrum of embarrassment and guilt) for our failures to care for our equipment.

Mask manufacturers routinely provide their “instructions” for cleaning, which typically take the form of daily disassembly, cleaning with soap and water, drying and reassembly. As previously noted, whether this is done simply to ward off litigation, or whether there is actual science and research underlying these recommendations, they are generally presented to users without factual explanation of their basis or origin.

One specific area of contention is that of the extent of mask disassembly required for thorough cleaning. The inconsistencies in manufacturer recommendations are telling. ResMed, for example, instructs complete disassembly of the Activa mask. This is not unreasonable; there are only 10 parts (excluding headgear), only one relatively small, fairly easily disassembled and reassembled (though I have done it improperly with resulting leaks). On the other hand, ResMed instructs only partial disassembly of the UltraMirage Full Face mask. This too is not unreasonable; there are some 13 parts (excluding headgear), six of which are relatively small, and those involved in the elbow and anti-asphyxia valve assembly require some level of dexterity and competence to handle safely and correctly. Loss of small parts down the sink is not unheard of. Obviously, there is a balance between the goals of cleanliness, and the goals of correct and non-destructive disassembly and reassembly. Some appropriate degree of balance must be found by each user. (I still have trouble properly replacing the UMFF venting system and cushion, for which ResMed does recommend daily disassembly.)

Other areas of concern involve whether the life expectancy of the delicate plastic cushion membranes are enhanced or lessened by the handling involved in disassembly and cleaning. This, too, involves personal issues of dexterity and confidence, as well as the development of good, safe practices.

The preventive measures of facial washing (possibly including the use of special cleansers or alcohol wipes to remove skin oils) before donning masks, and of course appropriate oral hygiene before bed, would seem appropriate. At the very least, daily rinsing of the fully-assembled mask appears to be reasonable. Gentle cleansing of the cushion surfaces in contact with the face, to remove grease and oils, may help in minimizing leak (though there are some who insist that either cleaning itself, or the process of disassembly and cleaning, increases the likelihood of leak). Periodic more thorough cleaning, including soaking in soapy water, with an appropriate level of disassembly, should not be neglected.

Finally, an industry has arisen which provides convenient “wipes” and “sanitizers” specifically for CPAP masks. Certainly better than doing nothing, I can’t help but wonder what research has been done, and what the use of such products actually accomplishes.

Headgear Straps

Finally, we move out of the realm of microbes, and into the personal comfort zone of dealing with our own head and hair greases and oils. Whether regular cleansing increases or reduces the lifespan of headgear is not at all clear. Washing certainly appears to vary the size and elasticity of some headgear materials, necessitating periodic readjustment of the straps (which is probably a good idea in any case). If a basin of soapy water left is over after having just given your mask a periodic cleaning, it seems wasteful not to give the headgear a dunking as well.

Concluding Comments

In the absence of reliable data, risk / benefit analyses devolve to decisions about what feels comfortable, and how much time and effort that comfortable feeling is worth. The wide spectrum of equipment cleaning practices frequently described on the CPAPTalk forum emphasizes that there are no simple answers which are always right for everyone.

On the other hand, if there’s visible crud anywhere on your CPAP system, be ashamed. And if you’re not regularly LOOKING for visible crud, be ashamed. Hygiene can be overdone, but that generally costs only time. Those of us with Sleep Apnea have a chronic condition which threatens our health, and failure to take appropriate care of our equipment and ourselves is at best short-sighted and risky. I’m not necessarily against risky behavior per se, but it seems as though it should be based on positive decisions rather than on laziness, and should deliver a lot more benefit (and fun).

--Velbor 23:45, 21 November 2009 (UTC)

updated --Velbor 15:25, 25 November 2009 (UTC)

released --Velbor 21:56, 29 November 2009 (UTC)

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