What is wrong with this scenario and what can be done to rectify it?

Your patient has a tidal volume of 600L and is inspiring over a period of 1 seconds. Currently he is receiving oxygen at an fiO2 of 40% by way of venti-mask. The white nozzle with the venti-mask specifies 8 L/min but he is currently at 10L/min (O2).

Asked by Aquiline, Last updated: Apr 20, 2024

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2 Answers

John Adney

(100-40)/(40-20) = 60/20 = 3/1

3 X 10 = 30 L/m Air
1 X 10 = 10 L/m O2
30 + 10 = 40 L/m total flow receive

3 X 8 = 32 L/m Air

3 X1 = 3 L/m O2

32 +3 = 35L/m requires

John Smith

Answered Sep 08, 2016

There is nothing wrong with this scenario-this question uses a number of different things to spin your head around, but if you go through the steps of calculating the inspiratory flow rate (.600/1)*60 = 36l/min.now that we know the patients flow rate, we can calculate what we are giving him with the current setup. at 40% the air:oxygen ration turns out to be 3:1 (100-40)/(40-20) = 60/20 = 3/1knowing that we can figure out that at 10l/min the patient is receiving 10l/min o2 + 30l/min entrained room air = 40l/min at fio2 of 40%.since the patient is receiving 40l/min and only requires 36l/min everything addressed in this scenario should be fine.interestingly enough, whoever didnt follow the guidelines on the nozzle knew that at 8l/min the patient would only be receiving 32l/min and would not get the full inspiratory requirement.strangely enough, i thought i was pulling these numbers somewhat out of the air but then noticed earlier that sibbersons uses the same sort of example (p.52).