Question

An oxygen flowrate of 12 L/min is used on a 60% Oxygen: air entrainment mask. What is the O₂: air entrainment ratio and total flow? ___________

Answer 1

To calculate the O₂: air entrainment ratio

The formula is

oxygen = FiO2 – 21   

air 100 - FiO2

Given data is

Oxygen flow rate = 12 L/min

FiO2 = 60%

Thus Oxygen = 60 - 21

Air 100 - 60

= 39

40

=0.975 parts of oxygen

1 part of air

That is 0.975 L/min of oxygen flow for every 1 L/ min of air flow. or O₂: air entrainment ratio is 0.975 : 1

Total flow = Oxygen flow rate + Air flow rate

Oxygen flow rate = 12 L/ min

Thus Air flow rate = 12 $\small \div$ 0.975

= 12.30 L/ min

So,

Total flow = Oxygen flow rate + Air flow rate

  = 12 + 12.30

= 24.30 L/min

Thus answer is, Total flow is 24.30 L / min