18 gauge - Diameters (mm)= 0.838 - Length= 3.0 cm 20 gauge- Diameter (mm)= 0.603

Question

18 gauge - Diameters (mm)= 0.838 - Length= 3.0 cm

20 gauge- Diameter (mm)= 0.603 - Length= 3.0 cm

22 gauge- Diameter (mm)= 0.413 - Length= 3.0 cm

24 gauge- Diameter (mm)= 0.311 - Length= 3.0 cm

26 gauge- Diameter (mm)= 0.260 - Length= 3.0 cm

A full IV bag contains 1 liter (1000 cm3) of saline solution ( = 10-3 Pa s). You'd like to deliver 1 bag to a patient over 2.5 hours. Assume you hang the bag high enough to create a pressure difference of 15,000 Pa across the needle.

Use the chart above numbers to determine the best needle to use.

A. 18 gauge

B. 20 gauge

C. 22 gauge

D. 24 gauge

E. 26 gauge

Explanation / Answer

Volume flow rate = *(pressure difference)*(pipe radius)4/[8*(pipe length)*viscosity)

=>    Q = Pr4/(8L)

=>    (0.001/9000)   =   3.14 * 15,000 * r4/(8 * 10-3 *L)

=>     r4/L   =   1.887 * 10-14

=>     best needle to use =    24 gauge                       (option D) is correct )

This is done by calculating r4/L from the above chart numbers .

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