Session 2 - Lung Mechanics

Question 1

what is tidal breathing

Answer 1

normal breathing without the use of accessory muscles

Question 2

true of false: tidal inspiration is passive

Answer 2

false - it is active. expiration is passive

Question 3

what is the pressure in the pleural cavity and why

Answer 3

it is negative as the 2 opposing forces of the chest wall and lungs cause the opening of this space. therefore a bigger volume gives a smaller pressure

Question 4

what is a pneumothorax

Answer 4

when there is air in the pleural space

Question 5

why does a pneumothorax cause the lung to collapse

Answer 5

the water tension between the 2 layers of pleural membrane is lost so they no longer stick together. therefore the elasticity of the lungs causes it to recoil

Question 6

what is compliance

Answer 6

the relationship between volume and pressure (volume/pressure)

Question 7

what happens to the compliance of the lungs in emphysema and why

Answer 7

they increase in compliance as they lungs have lost elastic tissue so can hold more air

Question 8

a deficiency in what can cause emphysema

Answer 8

alpha-1-antitrypsin

Question 9

how do you calculate ventilation rate

Answer 9

tidal volume x breaths per minute

Question 10

how does the compliance of the lung change in COPD

Answer 10

it increases

Question 11

how does compliance change in fibrosis

Answer 11

it decreases as the lungs become more stiff

Question 12

what is deadspace in the lungs

Answer 12

areas which there is air not being used for gas exchange

Question 13

what are the 3 types of deadspace

Answer 13

anatomic - air in the upper respiratory tract and terminal bronchioles
alveolar - air in alveoli which are being ventilated but not perfused
physiological - both

Question 14

what is the alveolar ventilation

Answer 14

(tidal volume - deadspace volume) x breaths per minute

Question 15

what is the value for tidal volume

Answer 15

150 ml

Question 16

what does surfactant do

Answer 16

reduce surface tension on alveoli

Question 17

how does surfactant prevent alveoli collapse

Answer 17

it makes the pressures the same in different sized alveoli so that air doesn’t move from smaller to bigger one preventing alveoli collapse of the smaller ones

Question 18

which accessory muscles are used in inspiration

Answer 18

SCM, scalene, pec major, pec minor, trapezius

Question 19

which accessory muscles are used in expiration

Answer 19

abdominal wall muscles, internal intercostal muscles

Question 20

true or false: the upper respiratory tract has a higher resistance than the lower

Answer 20

true as there is a smaller total cross sectional area

Question 21

how does loss of radial traction of airways occur

Answer 21

less lung tissue (e.g. in emphysema) mean theres less attachments of the airways to the lung tissue so they can’t be held open as well

Question 22

what is the functional residual capacity

Answer 22

the amount of air remaining in the lungs following passive exhalation

Question 23

what determines the function residual capacity

Answer 23

the balance of the outward expansion of the chest and the recoiling of the lungs