EBME Forums Forums Maintenance Technical Assistance Rainout in Neonatal Breathing Circuits

Hi folks
Our Neonatal Unit has a long standing problem with rain out in both Ventilator and NIV breathing circuits.
Devices affected include:
SLE 5000 with Intersurgical Circuits
Viasys SiPAP with F&P RT124 Circuits
F&P Chambers (autofeed for Vents, manual feed for SiPAP)

I would be interested if or how other Units tackle this issue.
it has been suggested we switch our MR850 Humidifiers into Manual HC mode but this needs further investigation. I believe there are some sort of circuit sleeves on the market available to fit around circuits and we are aware of F&P's Evaqua 2. Budget is obviously one of the biggest issues in addressing this.
Any advice would be greatly appreciated.
Topper

Topper,
I have come across this problem with the SLE5000 and Intersurgical circuits, it seems the power in the heater wire was insufficient. Changing to the heated expiratory limb circuits cured it.
I believe Intersurgical can provide prefitted sleeves but it is a long time ago so the memory might be failing me.

Another random cause of rainout was drafts, especially those caused by fans blowing on the patient.

Robert

Hi Tony
Further to Roberts tips, what temperature is the unit? The guidelines state it should be 22-26 degrees Celsius without any drafts.
Setting the 850 to manual control (0.0) would be my first step and keep the airway probe out of the incubator, as this can affect the humidification.
Mark

This is a strange one as, in my experience, neonatal unit "room temperature" is almost always too hot for comfort, rather than too cold.

The other interesting factor is, rather than one type of ventilator and one type of circuit being mentioned, we have a situation where various combinations all suffer from similar problems.

OK ... are we talking about one particular station (position in the room) here? The one right next to the HVAC duct (or open window, doorway, whatever) for instance. Or is this a more general problem?

Of course, we could also be heading up the Garden Path with that one ... maybe all the vent/circuit combinations are not the "ones of choice" anyway. Lack of heating "power" has already been mentioned - due (I suspect) to poor impedance matching. So ... have other (heated, supposedly) circuits been tried (like the ones recommended by the vent manufacturers, for instance)?

I spend a lot of time in Neonatal units and some are too cold, certainly below 22 degrees and one was 18 degrees, with horrendous rainout in the circuits (turning the ambient temperature up resolved the issue on this particular unit).

The common factors are the humidifier and the environment it is in. Neither the vent or ncpap will change the incoming gas temperature and humidity so the humidifier will do all of this but it is also affected by external factors. If the 850 is set to auto, it cycles over and under the set values by a larger margin compared to manual and once water droplets form it is very hard to correct this. Setting it to manual will control the temperature closer to the set value, limiting the amount of water droplets which will form. You may still get rainout, but it should be less over the same time period compared to auto.

Using auto-feed for everything will help but it will cost more and the water bag will inflate on the ncpap. A pressure sleeve on the bag helps to alleviate this but it shouldn't be a problem 'inflated' but it can make the nursing staff nervous.

Tony, give me a call if you want to discuss any of this.

Mark

Good answer, Mark ... and you're absolutely right (of course):- it's the humidifier that is the active device in all this - driving the heat and the moisture - as well as being the common component in all the set-ups mentioned.

But I can't help wondering about the temperature sensor (the "feedback loop"). Wouldn't a bad connection (or faulty "airway probe"), or some weirdness in its positioning also tend to cause temperature over (under) shoot and therefore contribute to - or indeed cause - rainout?

But first let's wait to hear from Topper about the ambient temperature in that Neonatal Unit!

i think its better to check the environment; temp. & humidity; as fare as i know temp in NICU should be 24-26; humidity 30-60%; and the variance in temp will sure lead to rainout. i believe temp control in the room is the best way to solve it.

OK folks many thanks for the suggestions so far.
I have investigated temperatures on the unit and canvassed opinion from Nurses. Digistats in the individual rooms indicate 28-30C (doesnt feel it though)but a central computerised control panel indicates the rooms are 26.0 - 26.3C. Our HVAC Tech in Estates assures the latter is the accurate readings. either way its not too cold. Nurses state it is a problem throughout but especially in 2 draughty bed spaces.
A quick look at all ventilatory devices in use shows circuits are visibly wet with lots of rainout, however this is "the norm" to me and because i have never seen a circuit in use without heavy condensate in it i have to ask is it (a rain out free circuit)actually achievable?
Mark, it was Owen who suggested the Manual HC mode to me. Obviously as a no cost option i would like to trial this but have concerns over the need for increased staff training and interaction with the MR850. For example if they are put into Manual mode will they retain this as default on power up? Also, service manual states that the user may have to alter the (0.0) setting to suit the conditions whilst in use, as i understand via a diagnostic hidden menu. Obviously this is asking for trouble but i would welcome your experiences before i speak to F&P about it.
Again many thanks to all.
Rojo, i will also keep in mind the suggestion of dual HW circuit - thanks.
Topper

What does your HVAC Tech say about room humidity, I wonder?

Meanwhile, the way I read the manual it seems to me that Activating and (or) Deactivating Humidity Compensation is retained for the next start-up - but this can be easily checked on site, can it not?

However, the MR-850 always starts up in "Invasive Mode" (that is, with a higher Chamber Set Point).

Topper
Even if the thermostat says that the room temperature is correct that does not mean that their are not local drafts near the vent.
I would also take a look at the siting of the end of tube temp sensor as has been mentioned above. If this is being heated by an over head heater of an incubator it will say that the end of hose temperature is correct and turn down the hose heater causing rain out.
Robert