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Oxygenation with BIPAP - Printable Version

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Oxygenation with BIPAP - Sleepy Willy - 06-23-2022

I was having a fight with my F30I the other night, as it's nearing its EOL and the air was shooting past the end of my nose.

I ripped off the F30I, which caused my sleep monitor to immediately start bitching about my O2 levels. So I put on my portable O2 concentrator which only puts out 1 lpm, at a reasonable noise level. I checked my Sleep Monitor the next day and my average O2 levels were 94%. My average O2 levels are never 94%. If I wear the BIPAP without O2, my levels are about 92%. If I wear the BIPAP with O2 (2 lpm) my O2 levels are 93%. How can 1 lpm be raising me to 94%.

I surmised that the BIPAP must be wasting a lot of the oxygen, through leaks and whatever you lose out of the exhaust ports. I asked the sleep doctor and he gave me a long winding story about the BIPAP altering your breathing patterns, so your body got less benefit from the oxygen. OK, I believe about 10% of that. I asked a sleep technologist I know and he basically said that if I had my large concentrator feeding 2 lpm to the BIPAP, I could only expect to get about .5 lpm to my body, which lines up with my real world experience. I guess my real question is why is this rocket science, if these people have any real world experience. The DME did not mention this, the sleep doctor seemed unaware of the loss factor and my other Respirologist made no mention of it, although to be fair, his prescription was only for my walk test.

Any experience with this or comments?


RE: Oxygenation with BIPAP - Sleeprider - 06-23-2022

When using oxygen with xPAP, the trick is to get the "fraction of inspired oxygen" FiO2 to a level that is sufficient to maintain your SpO2 and overcome the effects of dilution. I wrote the wiki on this topic and included the method for calculating FiO2 considering CPAP flow and mask venting. The problem is you have at least 30 L/minute of excess air in xPAP to satisfy respiratory requirements and avoid rebreathing expired CO2. With a cannula you get highly concentrated oxygen, even with a relatively low flow rate, but with CPAP you may need 3 to 4 times as much oxygen flow to match the FiO2 of a cannula, due to dilution of the oxygen with positive air pressure. http://www.apneaboard.com/wiki/index.php/Oxygen_Bleed_with_CPAP