respiratory: lung mechanics

Question 1

how to measure lung compliance

Answer 1

measure change in volume using spirometer

measure change in intrapleural pressure using oesophageal balloon

Question 2

where is lung compliance highest and when is it lowest

Answer 2

highest at tidal volume, lowest at TLC and RV

Question 3

what conditions make lung compliance extra low/extra high

Answer 3

extra low: fibrosis/ neonatal respiratory distress syndrome

extra high: emphysema

Question 4

what happens in bronchiolitis

Answer 4

thick narrow bronchioles with excess mucus

Question 5

what contributes to elastic resistance

Answer 5

elastin + collagen

air-fluid interface

Question 6

surface tension equation, what kind of tendency is there

Answer 6

P= 2T/R

small bubbles likely to collapse into big ones as force of surface tension is inwards

Question 7

what produces surfactant? what’s in it?

Answer 7

alveolar type II cells
phospholipids + surfactant proteins -> due to amphipathic nature of phospholipids, they float on surface of alveolar fluid lining

Question 8

what does surfactant do? how does it work

Answer 8

reduce surface tension in proportion to surface conc-> compliance increases,
alveoli doesnt collapse (especially in small alveoli), tendency to suck fluid in drops
as alveolus shirinks-> surfactant surface conc increases-> surface tension decreases-> P falls

Question 9

what’s neonatal respiratory distress syndrome

Answer 9

premature babies dont produce enough surfacant -> reduced compliance and alveolar collapse

Question 10

how else do alveoli resist collapse

Answer 10

alveoli join together

Question 11

obstructive lung disease vs restrictive lung disease

Answer 11

obstructive lung disease: airways not ok/high resistance-> air cant flow down tubes
restrictive lung disease: trouble expanding thoracic vol/cant overcome tendency of lung collapsing inwards eg fibrosis/respiratory muscle weakness/phrenic nerve damage

Question 12

two conditions of COPD

Answer 12

emphysema and chronic bronchitis

Question 13

what happens in asthma, chronic bronchitis and emphysema

Answer 13

asthma: bronchoconstriction, mucosal oedema
chronic bronchitis: hypertrophied glands, mucous production, wall damage, narrow airways
emphysema: elastic tissue unable to hold airways open, alveoli destroyed

Question 14

what happens in lung fibrosis and respiratory muscle weakness

Answer 14

lung fibrosis: stiff alveoli, scar tissue

respiratory muscle weakness: airways and alveoli normal, respiratory muscles weak

Question 15

ways to measure airway resistance

Answer 15

body plethysmograph
peak flow
forced expiratory vol vs time

Question 16

whats FEV1 and FVC, whats normal value of FEV1/FVC

Answer 16

FEV1 is forced expiratory vol in 1 sec
FVC is forced vital capacity (total amt u can force out)
normal value is 75%

Question 17

how are FEV1, FVC and FEV1/FVC values affected in obstructive and restrictive diseases

Answer 17

obstructive: FEV1 low, FVC normal/low, FEV1/FVC low
restrictive: FEV1 low, FVC low, FEV1/FVC normal

Question 18

how are maximum flow-volume loops affected by obstructive/restrictive lung disease

Answer 18

obstructive: left-ish; concave appearance of forced expiratory curve
restrictive: right-ish, normal shape, peak flow is lower

Question 19

what happens to FRC in lung fibrosis and emphysema

Answer 19

fibrosis: reduced FRC
emphysema: increased FRC