Chapter 19 Drains

Question 1

What is Laplace’s law in regards to bandages?

Answer 1

The pressure applied under each point under a bandage is proportional to (N x T)/(R x W)

N=number of bandage layers, T=bandage tension, R=radius of curvature of body part, W=width of bandage material under tension

Question 2

What is the pressure at which arterioles to the skin and to the underlying muscle are compromised?

Answer 2

• Skin 30mmHg
• Muscle 50mmHg

Question 3

What pressures can be generated by a grenade bulb using various methods of compression?

Answer 3

• 170mmHg when rolled from apex to base
• 110 when compressed with 2 hands
• 84 when compressed with 1 hand

Question 4

Doubling a drain diameter increases flow by how much?

Answer 4

16 fold

Question 5

Halving a drain length increases flow by how much?

Answer 5

2 fold

Question 6

Flow is propotional to radius ^ __
inversely proportional to ____

Answer 6

4th, length

Question 7

When should you remove a drain?

Answer 7

when flow is <0.2ml/kg/hr