Heated humidifiers, CPAP vs ventilator; Nafion as alternative?

[runcyclexcski]

Hi all,

As you may guess from my naiive questions below, I am quite new to the field (I apologize in advance). I am looking to purchase a standalone heated humidifier. Looking at the F and P units at the moment, but they all look the same (water pots with a heater plate and a thermostat). F and P seems to have CPAP-oriented h-fiers and breathing machine-oriented h-fiers, with a significant (3-5x?) difference in cost between the two. May I ask what the difference is (power rating seems similar) and if there is any advantage of getting the (more pricey) breathing circuit-oriented machine? If I get the breathing circuit-oriented one, will I be able to use it with a CPAP? I was going to use my own custom-made PTFE hose, not the standard heated wire hose, due to concerns of plastic odor in the standard heated wire hoses. Will I be able to run a heated h-fiers w/o their heated hose plugged in?  (I guess I could fool it into thinking it had the hose plugged in by adding a resistor. May be the engineers here know which pins to use  ).  


On a separate note -- are there more advanced CPAP humidifiers than mere heated pots? I would eventually like to build a ventilator which I could put on a cart and take on walks and to work.  So I wonder if there are solutions that would be resistant to shaking and spliing of water into the breathing tube. My plan was to try PermaPure nafion humidifiers. However, these are not rated for medical use (they are for hydrogen fuel cells), thus, I am having concerns about what may end up in the air flow (Nafion precursors are nasty compounds), and the cost is quite high -- 1.5K for the Nafion cassette alone (a bundle 780 tubes, 7" long).

[SarcasticDave94]

I've not looked at which model was what in a while. The ventilator versions might be higher output to keep up with higher airflow, but I don't know of any specific advantages for either. Pre-manufactured or bulk hose are both likely to work, as my Fisher and Paykel Vitera mask is supposed to work with CPAP and ventilators. I'm referring to the mask connection expected to be the same size, indicating that the hoses will also be similarly sized.

Fisher and Paykel also have a heated hose kit that should get you that feature. It's probably intended for a ventilator, so look in that area.

[runcyclexcski]

Many thanks Dave! The specs for both types seem to be similar (up to 120 LPM air flow). I wonder if ventilator one has a feedback loop based on humidity whereas the CPAP one has a feedback loop based on the temperature of the pot, and one would have to adjust the latter by trial an error ("comfort"). I have a humidity sensor, so it should be no problem for me to reach the set point with the CPAP one, I guess (I would like to have >90% at 37C at the output).

I was going to heat my PTFE hose by wrapping it with a silicone tube coil and running water through that. Insulate the hose on the outside. This way I would avoid overheating the hose, and I would have an independent feedback loop for the hose (I would keep it, say, at 40C).

I did find the kit with the heated hose version of the F and P, and I am worried that if I do not plug in their native hose (i.e. the electrical plugs in it), the unit will refuse to run.

[runcyclexcski]

P.S. if I cannot reach the set point and the temp I want, I am thinking to run two humidifiers in series.

[SarcasticDave94]

I think the redundant humidifiers won't help, but will add complexity and price without any notable gain.

[runcyclexcski]

Dave -- OK. I will start with one cheap HC-150, see what I get, and then go more expensive if needed. Two HC150s are still cheaper than one fancy ventilator one.

After more reading it looks like my initial guess might be correct -- the cheap/CPAP F and P HC150 unit does not have a feedback loop based on the measured params of the humidified air, and it's up to the user to find the setting (which looks analog) of the heater at which they have benefits from the humidity, but no rain-out yet. The ventilator-coupled units do track the humidity and the temp of the output and adjust it (b.c the patient might not be in capacity to provide "feedback" in the ICU). The HC150 unit only seems to have a "ambient tracking" feature. I guess it measures the humidity and the dew point of the ambient air. If that "smart" feature prevents me from getting the humidity I want I can always fool the unit (e.g. keep it in a desiccated box).

[SarcasticDave94]

Here's the F&P humidifier models I'm seeing besides your mention of HC150

MR850 heated humidifier, lighted digital display, probably for ventilator duty, blue and gray color, has flow sensor

MR810 respiratory humidifier, 3 power level, off white

F&P 550 Respiratory humidifier, off white

I saw no price info

[runcyclexcski]

Dave -- a new MR850 is £1250 on ebay right now with "no returns accepted" (prob some surplus unit the seller got a hold of).

(ebay ID 115021626442, I can't post http links yet).

Used MR850s seem to be $300-$800, depending on the condition (all on ebay).

So, for now I ordered an HC150, to get a datapoint and see how far off I am. I can post RH and t measurements here. For testing, I use a turbo unit and a heated wire anemometer, so I can post the air flow as well.

[SarcasticDave94]

OK copy. Sure let us know if it works out.