Active and Passive Respiratory Forces

Question 1

Understand the concept of recoil

Answer 1

• Any time one exerts a force to move an elastic object, that object will exert a recoil force to return to rest
• If object is distorted from its rest position, the direction
• of recoil is opposite from distorting force
• Recoil force will increase as an object is further distorted

Question 2

Know the resting position of the lungs, the thorax, and the lung-thorax unit

Answer 2

LUNGS = 0% VC

THORAX = 55% VC

LUNG-THORAX (EEL) = 35-40%

Question 3

Understand how recoil (passive) pressures are generated

Answer 3

Lungs & thorax are ELASTIC

Question 4

Know how to interpret the “Recoil Pressures” diagram

Answer 4

35% of VC at 0 cmH20 alveolar pressure = at rest

Different percentages of VC show positive or negative pressure!

Question 5

Understand the difference between recoil pressures and muscular pressures

Answer 5

Muscular pressure will be superimposed on recoil pressures

• Muscular (active) component is volitional
• Recoil (passive) component is not volitional
• Simultaneous passive and active forces

Resulting change reflects the net effect of passive and active forces