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Wiki article: Oxygen feed into BiPap system - Sleeprider - 03-10-2018
Could one of you engineers check my math here? To calculate the concentration of oxygen in CPAP diluted air
(oxygen flow rate (litres) at 100% + air volume (litres) at 21% O2) / Total air volume = oxygen concentration
therefore, at 3 litres/minute oxygen addition and assuming a total CPAP flow of 60 L/min:
(3L x 100) + (60L x 21) = 1560 / 60 L/min = 26% oxygen.
at 1 litre/minute oxygen
(1L x 100) + (60L x 21) = 1360 /60 L/min = 22.% Oxygen.
Conclusion, a 1-litre oxygen bleed into CPAP results in a 1% increase in oxygen after accounting for the CPAP dilution.
Edit to add: I just created a new Wiki for Oxygen Bleed with CPAP. I'd appreciate your ideas on how to enhance or improve this wiki. Thanks to this thread and its contributors for the idea that we needed this.
http://www.apneaboard.com/wiki/index.php?title=Oxygen_Bleed_with_CPAP
RE: Oxygen feed into BiPap system - ShaunBlake - 03-10-2018
(03-10-2018, 07:52 PM)Sleeprider Wrote: ...
Editto add: I just created a new Wiki for Oxygen Bleed with CPAP...
Great idea; I hope I'm not the only one who is pleased and relieved that we (you) are taking this bold step.
I hope I'm not treading my clumsy combat-booted feet in somebody's garden by suggesting that we have a separate thread for this conversation.
Do you intend to use Severinghaus' formula?
SO2 = (23,400 * (pO23 + 150 * pO2)-1 + 1)-1
Is Sainsbury's calculation (Oxyhemoglobin Dissociation Curve) too complex (involved)?
RE: Oxygen feed into BiPap system - SarcasticDave94 - 03-10-2018
I, being a non-engineer type, will go duct tape my head so it doesn't explode. I'll trust y'all got this right. I soon may be adding oxygen concentrator to my list of DME products. Hence why I'm curiously following along; as best as my lil brain can that is.
RE: Oxygen feed into BiPap system - JesseLee - 03-10-2018
Just at a quick glance, the divisor of 60 should be 63. 60l + 3l = 63 liters total flow. Oxygen flow plus cpap flow.
(3L x 100) + (60L x 21) = 1560 / 63 L/min = 24.76% oxygen.
(1L x 100) + (60L x 21) = 1360 /61 L/min = 22.3% Oxygen.
Small changes. If I'm wrong please tell me.
RE: Oxygen feed into BiPap system - ShaunBlake - 03-10-2018
(03-10-2018, 09:48 PM)SarcasticDave94 Wrote: I, being a non-engineer type, will go duct tape my head so it doesn't explode. I'll trust y'all got this right. I soon may be adding oxygen concentrator to my list of DME products. Hence why I'm curiously following along; as best as my lil brain can that is.
I din'think of it before shelling out for an O2 concentrator; I'm hoping you can benefit from this ideer before you sacrifice your first-born: switch to drip instead of perk and you may get enough O2. BTW, I'm pretty sure those K-cup machines leach all the O2 out of the water... I'm still trying to figger what's left but all my probes dissolve before I kin git a reading. : ROFL:
RE: Oxygen feed into BiPap system - SarcasticDave94 - 03-10-2018
No worries folks, no one in particular was harmed in trials for Nespresso Oxygen Concentrator.
I had a COPD suggested Pulmonary Function Test Friday 3/09/18, tech said off-the-record like that she didn't see great COPD progression. I have tested with same tech at my pulmonary doc's office 3 times since diagnosis for COPD was handed down. I see the doc in about 2 weeks for an official update, where I'll be asking again about oxygen as a possible new addition to help breathing, both overnight mixing it with the ASV and O2 use during the day. Retired doc said I won't need it because that "makes you look like an old person"!
DUCK...I like that doc so much more after he retired... 
RE: Oxygen feed into BiPap system - Sleeprider - 03-11-2018
(03-10-2018, 10:04 PM)JesseLee Wrote: Just at a quick glance, the divisor of 60 should be 63. 60l + 3l = 63 liters total flow. Oxygen flow plus cpap flow.
(3L x 100) + (60L x 21) = 1560 / 63 L/min = 24.76% oxygen.
(1L x 100) + (60L x 21) = 1360 /61 L/min = 22.3% Oxygen.
Small changes. If I'm wrong please tell me.
Correct! Thanks!
RE: Oxygen feed into BiPap system - Sleeprider - 03-11-2018
(03-10-2018, 09:07 PM)ShaunBlake Wrote:(03-10-2018, 07:52 PM)Sleeprider Wrote: ...
Editto add: I just created a new Wiki for Oxygen Bleed with CPAP...
Great idea; I hope I'm not the only one who is pleased and relieved that we (you) are taking this bold step.
I hope I'm not treading my clumsy combat-booted feet in somebody's garden by suggesting that we have a separate thread for this conversation.
Do you intend to use Severinghaus' formula?
SO2 = (23,400 * (pO23 + 150 * pO2)-1 + 1)-1
Is Sainsbury's calculation (Oxyhemoglobin Dissociation Curve) too complex (involved)?
I'm not familiar with the Sainsbury calculation, but will research it. I'm not a medical professional, and the formula I proposed comes from my air quality modeling background to determine the concentration of a mixture. Let me see if I can figure out this formula, and I'll add it once it makes sense and I'm comfortable with it.
Part of my interest in developing the wiki is to put it out on the web that oxygen bleeds into a CPAP/BPAP circuit are highly diluted, and may not have the intended therapeutic impact at low bleed rates. This is unlike applying O2 via a canula or nasal prongs. XPAP has very high exhaust rates, that are pressure dependent. I may include some charts to show what these anticipated flow rates are. This flow rate curve is from the Resmed Swift FX mask which has a lower flow rate than a full face mask.
![[Image: SwiftFX-chart_zps1a3bc596.jpg]](http://www.apneaboard.com/wiki/images/e/e7/SwiftFX-chart_zps1a3bc596.jpg)
RE: Oxygen feed into BiPap system - Sleeprider - 03-11-2018
I made some pretty substantial changes to the Wiki. Appreciate the input from this group. http://www.apneaboard.com/wiki/index.php?title=Oxygen_Bleed_with_CPAP
The revisions incorporate the correction by JesseLee, and the calculations are now based on a much lower flow rate based on a Resmed Table that shows several masks and shows the relationship of design flow and pressure. Lots of formatting changes and improved explanations. The calculations section now looks like this:
The equation to calculate concentration from flow is:
(oxygen flow rate (litres) at 100% O2) + (air volume (litres) at 21% O2)) / Total air volume = oxygen concentration Percent in circuit
therefore:
at 1 litres/minute oxygen addition at 100% and assuming a total CPAP flow of 30 L/min:
(1-L/min x 100) + (30-L/min x 21) = 730/31-L/min = 23.55% Oxygen.
at 3 litre/minute oxygen at 100% and assuming a total CPAP flow of 30 L/min:
(3-L/min x 100) + (30-L/min x 21) = 930/33 L/min = 28.18% oxygen.
Any variable can be changed based on available data. If the flow rate is 40 L/min from the CPAP, the oxygen concentrations will be lower. If leaks are present or pressure results in a higher average vent-rate, the oxygen concentrations will be lower.
For oxygen concentrators, it is important to use the oxygen percent output by the concentrator. While bottle oxygen is pure at 100% oxygen, a concentrator may put provide a concentration of 75% to 80%. The proper value can be determined from the machine specifications and input to the formula.
![[Image: Resmed_Pressure_vs_Flow.png]](http://www.apneaboard.com/wiki/images/7/79/Resmed_Pressure_vs_Flow.png)
RE: Oxygen feed into BiPap system - SarcasticDave94 - 03-11-2018
Thanks for the nice info post on Pressure vs Flow.