Sun28November0440PM 17

A patient is receiving oxygen therapy via a venturi mask.

The air entrainment ratio is 1:9 (1 litre of 100% oxygen from the central source entrains 9 litres of air from the atmosphere). The flow rate of 100% oxygen is 6 L/minute.

Which value approximates to the oxygen concentration delivered to the patient?

(Please select 1 option)

24%

35%

28% Correct

60%

40%

Explanation

The air:oxygen entrainment ratio can be determined using the formula:

100% - FiO2 = air/oxygen entrainment ratio

FiO2 - 21%

The entrainment ratio is already known. Substituting the values in the equation: x = FiO2.

100 - x = 9

x - 21

100 - x = 9(x - 21)

100 - x = 9x - 189

10x = 289

x = 289/10

x = 28.9%

The total flow received by the patient can also be calculated:

Total flow = source gas flow + source gas flow × entrainment gas ratio

In this example:

Total gas flow = 6 + (6 × 9) = 60 L/minute.

Answer Statistics

1

6%

2

16%

3

57%

4

11%

5

12%

Times answered: 241