WHAT IS 'ACTUAL DOSAGE' AT THE TREATMENT PRESSURE INSIDE A HYPERBARIC CHAMBER?
INSPIRED FRACTION OF OXYGEN
What is the "actual dosage" inside a hyperbaric chamber?
* The dosage is referred to as the Inspired Fraction of Oxygen (IfO2)
The formula for all chamber is the same - Tier 1, Tier 2 & Tier 3.
* Inspired Fraction of Oxygen (IfO2) = (concentration of O2 (fO2) x mask efficiency x the treatment pressure (in ata)
Inspired Fraction of Oxygen (IfO2)
At Sea Level
Sea level breathing "normal air" (21%)?
* IfO2 = 21% (.21) x sea level pressure (1 ATA) = 21% IfO2.
Air Pod does NOT use an Oxygen concentrator.
The patient is breathing pressurised 'air' at 1.3 ATA.
* IfO2 = 21% (.21) x 1.3 (ATA) = 27.3% IfO2.
** Air Pod: IfO2 = 27%.
What is the "real" dose inside a soft & mild HBOT chamber using an Oxygen concentrator?
Oxygen concentrators only provide between 5-10 LPM.
However the average person requires at least, 15-20 LPM inside a hyperbaric chamber.
Where is the balance of "Oxygen" coming from?
* Typically the occupant and operator will turn up the flow rate in order for the occupant to 'feel' that they are getting enough air. However this dramatically LOWERS the actual concentration of oxygen to the occupant.
** 93% suddenly become significantly less and typically as low as 50%.
* Virtually all soft and mild chambers use inexpensive disposable masks and rebreathing systems using a "1 litre bag". The masks do not 'seal onto the face' and provide considerable leakage between the mask and face.
** The leakage can be as much as 10-15%, or greater.
Now we must allow for the decreased O2 concentration (efficiency at 50%) and mask leakage (efficiency at 85%).
- IfO2 (in ata) = (concentrator fO2 x mask efficiency) x the treatment pressure (in ata).
The 'actual dosage' formula:
* IfO2 = [50% from the Oxygen concentrator x 85% mask efficiency = 42.5%] x 1.3 (ATA) = 55.25% IfO2.
** The Actual Dose breathing the "advertised" 94% O2 @ 1.3 ATA = 55.25%.
Dosage at Tier 2 and Tier 3 Chambers
Tier 2 and Tier 3 systems provide 100% O2 without mask leakage using a BIBS or Hood system.
Using the treatment dose formula: PO2 = [100% (1.0) Oxygen x 100% (1.0) mask efficiency = 1.0] x Treatment pressure (ATA)
* PO2 = [100% (1.0) Oxygen x 100% (1.0) mask efficiency = 1.0] x 2.0 (ATA) = 2.0 ATA
** 2.0 ATA is the correct treatment dose.