Author Question: The therapist is using an O2 flowmeter set at 15 L/minute to deliver an 80-20 helium-oxygen gas ... (Read 33 times)

silviawilliams41 · **on:** Jul 16, 2018

The therapist is using an O2 flowmeter set at 15 L/minute to deliver an 80-20 helium-oxygen gas mixture. Calculate the actual flow that the patient is receiving.

A. 8 L/minute
B. 12 L/minute
C. 18 L/minute
D. 27 L/minute

Question 2

Which of the following factors associated with heliox tend to decrease the Reynold's number? I. density of helium II. viscosity of helium III. specific gravity of helium IV. molecular weight of helium

A. I, II only
B. I, II, IV only
C. I, II, IV only
D. II, III, IV only

bimper21 · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: D
A. Incorrect response: See explanation D.
B. Incorrect response: See explanation D.
C. Incorrect response: See explanation D.
D. Correct response: When an 80-20 heliox mixture flows through an O2 flowmeter, the therapist must multiply the flow indicated on the flowmeter by 1.8 to determine the actual flow of heliox the patient is receiving. An O2 flowmeter is calibrated for O2 mixtures only, and not for heliox. Therefore an O2 flowmeter set at 15 L/minute will deliver about 27 L/minute of heliox to the patient, that is,
15 L/minute 1.8 = 27 L/minute
The factor for a 70-30 heliox mixture is 1.6, and for 60-40 is 1.4.

Answer to Question 2

ANS: A
A. Correct response: Whether flow is laminar or turbulent is indicated by the Reynold's number, that is:
Reynold's number = (velocity) (density) (diameter)
viscosity
Because helium has a lower density and a higher viscosity than air, heliox tends to produce a lower Reynold's number, and favors the development of laminar flow. A Reynold's number of less than 2,000 supports laminar flow, and a Reynold's number greater than 2,000 promotes turbulent flow.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.