Performance test of 7 CPAP humidifiers [ENG]

Humidifier in a CPAP device is nowadays absolutely obligatory. Today, even devices on an economy shelf are equipped with a water tank, often as an integral part that cannot even be disconnected. This is not a coincidence because the humidifier not only increases comfort but also increases the safety of the therapy by protecting delicate lung tissue from irritation and directly improves the results of apnea treatment. In case of problems with the acceptance of the therapy (compliance), the humidifier settings are always checked at the beginning. 


At first sight, a humidifier is nothing particularly complicated. A plastic tank through which air is passed through, which is additionally equipped with a heating plate (or built-in heater). In practice, this element requires a lot of engineering work to perform its role well. It must be easy to use and durable because the user will change water in it every day and wash it just as often. It should be safe for the device to prevent water from entering the CPAP during installation or small movements during use. Its role is also important in silencing the sound of the machine (most humidifiers silence the apparatus but there are also inferior constructions that work the other way around). But in the end the most important thing is of course the humidifying efficiency. 

By humidifying efficiency we mean the amount of grams (millilitres) of water that the humidifier is able to evaporate in a unit of time (hour). Several factors influence the efficiency:

  • size of the evaporation area
  • heating efficiency
  • the method of air distribution (time of air passing through the humidifier and the flow)
One might wonder if measuring the humidification efficiency makes any sense, since there are nights
Flow control plugs

when we use no more than barely 100-150 ml of water. However, this parameter is very important in the following situations:
  • the rate of hydration at the start of the therapy (in winter, CPAP "gives us a burn" before the moisturizer gets warmed up)
  • humidifying capacity at high pressures and leaks (water demand then increases many times)
  • passive humidifying power (without heating) allows to lower the temperature while maintaining high humidity, which increases comfort especially in hot months

    Humidifiers have various designs. They stand out here:
    • Humidifiers integrated as in ResMed AirSense 10, Lowenstein Prisma (the humidifier is also a tank)
    • humidifiers with internal water tank (Philips Dreamstation, RemStar Pro)
    • humidifiers with simple airflow design (Philips Dreamstation, Apex iCh)
    • humidifiers trying to control air movement (AirSense) or even containing special partitions extending the time of air flow through the humidifier (Prisma)
    • humidifiers with a plate heater at the bottom (most) or a heater built into the humidifier (Prisma)
    • humidifiers with constant (most) and pulsed humidified air supply (DeVilbiss)
    Test stand

    To be honest, starting this test, I immediately had my suspicions about how it might turn out. I was sure that ResMed will do well, because I use it on a daily basis and it seems to have a very well thought-out design (I am a demanding user).  I knew from previous tests that some Chinese devices have a big problem with this design element. I have never had problems with the Philips Dreamstation but, to be honest, I have never trusted a simple design that only blows air onto the water surface and does not try to combine with the flows. The silent leader was Prisma because its humidifier is simply huge (the size of an average CPAP) and a rubber "labyrinth" for air is mounted inside. Only a small heater installed in the tank itself (low heating surface... but no intermediate elements) was of some concern here.

    It took us a long time to design the test itself, so that its results could be considered reliable. The final procedure was as follows:
    • all humidifiers are filled with the same amount of water (250 ml)
    • all operated for exactly the same length of time (90 minutes), simultaneously, in one room
    • Humidifiers were set to maximum heating, fixed pressure 10 cm H20, all additional functions that could affect the test result were disabled
    • instead of the mask/tube, we installed "standardized" plugs, with the flow set to 40 l/ minute at 10 cm H20, which corresponds to the normal use of the Amara series mask, with an additional leakage of 15 l/min. In other words, quite a "life" situation.
    • The water in the humidifiers at the start of the test was 19 degrees Celsius (the so-called "cold start"), the test was carried out in a room with good ventilation, temperature 20 degrees and relative humidity 62%.
    • the amount of evaporated water was measured on a very precise laboratory scale (we we weighed the whole humidifiers before and after the test, calculating the amount of weight loss)
    • we repeated the test twice to verify the results

    The test results are as follows:

    1. Philips Dreamstation                               42,0 g H20/ hour
    2. Philips RemStar Pro                                40,2 g H20/ hour
    3. Lowenstein Prisma                                  38,5 g H20/ hour
    4. ResMed AirSense (AirCurve) 10            37,9 g H20/ hour
    5. BMC Resmart G2S                                  28,6 g H20/ hour
    6. Apex iCH                                                   13,8 g H20/ hour
    7. Resvent iBreeze 20A                                11,4 g H20/ hour
    As a subjective level of comfort for my person I consider 30 grams per hour (ResMed comfortable, BMC OK, below drama). The results have of course been recalculated, because the test lasted not 60 but 90 minutes. We also measured the water temperature at the end of the test - everywhere it ranged between 38 and 40 degrees. I always thought that the temperature in the humidifier will be higher. 


    1. It is clear that branded devices are clearly escaping the Chinese competition - clearly in this area new companies still have a lot to learn.
    2. Philips Dreamstation is the best example that even a seemingly primitive but well thought-out design can outclass the competition; if it wasn't for the fact that Philips was in second place too, I would have suspected that maybe it was just a coincidence but now I think it is a good engineering job.
    3. A slight disappointment for Prisma, because although she was at the top of the test, I expected her huge and complicated design to outclass her rivals (perhaps it's the heater's fault or the flow finishes).


      The most efficient, best humidifier on the market is Philips Dreamstation. Bravo!


      Please remember that the efficiency of the humidifier is not everything. It is also important to be able to use a heated tube (it is no use if the water condenses before the air flows into the mask).If you do not use a heated tube, it is important that the device is able to maintain relative humidity as it does otherwise...  In the Philips Dreamstation and probably no other device in the world can do that. 

      Lowenstein Prisma
      Philips RemStar
      Apex iCH

      Philips Dreamstation
      BMC Resmart
      ResMed AirSense

      Resvent iBreeze

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