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→What is the oxygen concentration in the diluted CPAP circuit?
=What is the oxygen concentration in the diluted CPAP circuit?=
The equation to calculate concentration from flow isa simple mass balance:<br>
(oxygen flow rate (litres) at 100% O2) + (air volume (litres) at 21% O2)) / Total air volume = oxygen concentration Percent in circuit <br>
therefore:<br>
'''Scenario 1'''at 1 -litres/minute oxygen addition at 100% and assuming a total CPAP flow of 30 L/min:<br>(1-L/min x 100% O2) + (30-L/min x 21% O2) = 730/31-L/min = '''23.55% Oxygen'''.<br><br>
'''Scenario 2'''at 3 -litre/minute oxygen at 100% and assuming a total CPAP flow of 30 L/min:<br>(3-L/min x 100%O2) + (30-L/min x 21% O2) = 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 also be lower. If a mask with less vent rate is used, then concentrations of oxygen will increase.
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.
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