Help? Oxygen level and ResMed Astral 150

[Helena]

My mother's oxygen level stays steady on the canula.

When we switch her to the vent (ResMed Astral 150) at night, we have to turn up the oxygen level some.

I think there is an oxygen leak in the vent somewhere.

Last night, I ended up having to turn up the oxygen from ca. 2.6 liters (where it is set for her canula) to 4.4 liters to keep her oxygen level high enough (93-96)

A sleepless night of oxygen checks and turning the concentrator up.

New hose from concentrator to vent, no kinks, no splits. Mask fits well, no alarms going off.

Someone from the DME is coming to do a machine check today.

What should I ask them to check?



Thanks very much.

[Sleeprider]

Helena, any ventilator uses more air-flow than is required to be respired. This is to ensure that air won't be re-breathed. The oxygen supplied by a canula is not as diluted as when it is injected into the airflow of a ventilator. The doctor estimates the oxygen flow to increase the fraction of inspired oxygen (FiO2) above the normal atmospheric concentration to meet a patient's needs. When that oxygen is delivered through the ventilator circuit rather than a canula, the oxygen flow must be increased. This wiki we wrote explains this problem in both basic and detailed terms http://www.apneaboard.com/wiki/index.php..._with_CPAP

It is possible to estimate the required oxygen flow in Liters per Minute that must be delivered, depending on the vent pressure and designed leak rate of the mask. It appears you have figured this out by titration. Be assured this is normal, but requires some expertise to understand the difference between oxygen delivery via canual and via ventilator.

[Helena]

Sleeprider, thank you very much. Fascinating reading! I appreciate your help.

My concern is that the oxygen level for the vent is having to be turned up higher now than in the previous months, although the level of oxygen required for the canal is lower than she has sometimes needed.

[Sleeprider]

What you describe is a normal difference between FiO2 delivered through a canula, and the need to increase the concentrator flow output to maintain the same FiO2 with a vent. We have seen individuals that use 2-L/min O2 during the day by canual, require 4 to 5 L/min when that oxygen is delivered through a vent or CPAP. Perhaps you are saying that you are needed to increase oxygen flow higher than you have in the past, assuming the ventilator and mask setup is the same? A common reason that SpO2 will drop significantly is if the leak-rate at the mask or anywhere else in the Vent circuit increases. The vent or CPAP must increase flow significantly to maintain an effective pressure when leaks are present. This means any oxygen bleed will be diluted more than when leaks are not present.

We have an Advisory Member Staceyburke that uses 5 L/min supplemental oxygen. When he has developed leaks, his SpO2 drops significantly. I'll have his stop by this thread.

[LindanHotAir]

There are several factors that change the airway resistance and the breathing. It can be affected by how well any bronchodilator drugs are inhaled, nasal congestion, or pain medication. Some adjustment is needed to compensate for daily fluctuations as they occur.  The DME normally checks the oxygen concentration delivered by the concentrator.  Be aware that most concentrators max out at 5 liters, and if you find that is not sufficient, you will need her prescription and concentrator changed. We eventually needed a 10 liter machine that we had to put in a different part of the house with a long tube because of the heat and noise of 2 compressors.

[staceyburke]

I have used O2 for about 15 years. I have to increase 2 L to keep O2 levels up at night 

I would purchase a cheap night time O2 monitor. They will cost 100 - 150   Make sure it records the Entire night. I have cms 50f. You don’t need to monitor every night but once ever 2 to 3 weeks.

[Helena]

Sleeprider, thank you so much for the explanations. They are very helpful. I appreciate your kind help.

Lindan, thanks. It is good to know what might lie ahead. I appreciate your help.

StaceyBurke, thanks for your post. I was wondering if I could monitor all night, and have it alert me if oxygen goes too high or too low.

I will look into the cms 50f.

Still waiting for the DME tech to come check the vent.

On hold, again, with DME, waiting for answers.....

[staceyburke]

Just a note. Any O2 monitor will have spikes (down) because of movement and poor contact with the probe. I would not set anything to wake you up. Rather look to see if you go under 88% for minutes during the night which would mean O2 might be needed at night. 

Again everyone will have some low spikes it is the duration under 88%.

[SarcasticDave94]

The CMS 50F has a user set low oxygen alarm. I found that mine went off frequently and cancelled it. I can feel when my oxygen levels drop making the alarm a pest.

Also I think the Astral 150 should have some alarms if you feel those may help in monitoring.

[Helena]

Pulmonologist is running some monitoring tests tonight. I am to write down oximeter numbers several times and record time and number. RT was here and said that one thing that could be making the oxygen level read lower on the oximeter is that the volume of air coming into the thoracic area from the vent makes the heart pump in a less expansive way and that the fingers could have less of a pulse for the oximeter to read.

Depending on what the read-out is (which the vent sends to the doctor's office), there may be an overnight oxygen monitoring test coming up.

RT said that pulmonologist said not to increase oxygen level on the concentrator above 3 for now.

My mother is on the vent because her body does not expel carbon monoxide well.

Increasing oxygen could cause problems with carbon monoxide.

I am to wait for further instructions.

Stacyburke, thanks for bringing up the duration of low oxygen times. That is part of what they are checking long distance from all the info the vent collects.

SarcasticDave, thanks for mentioning the alarms. I asked the RT about setting the alarm for low oxygen levels. She said, "No" for now. RT said I should check for symptoms more than oximeter numbers, at this point.

I am to check mask fit at low oxygen times. She is to take deep breaths and see what that does, for now.


Thank you all for you help and kindness. I appreciate it very much.