Lung Mechanics 2 #2 Flashcards
(41 cards)
How does surfactant lower T of alveolar lining fluid?
- phospholipids have insol FA end + hydrophil end
- therefore float on surface of alveolar lining fluid - gets inbetween H2O mol trying to get close together
- red T of alveoli in prop to surface conc of surfactant on alveoli
What happens to surfactant as alveolus shrinks + result?
- conc inc as mol closer together so T falls
What happens to P in small alveolus as surfactant inc?
- even though r dec, T now lower so P falls + doesn’t rise as alveolus shrinks
What is effect of surfactant on compliance + why?
inc it as now easier to expand lung as stiffness + amount it wants to collapse in dec by dec T
What other effects does surfactant have?
- red tendency for alveoli to collapse - esp effective in small alveoli where surface conc of surfactant v. high
- red tendency to suck fluid into alveoli (transudation) caused by collapsing P
What is neonatal respiratory distress syndrome?
- occurs in premature babies due to inadequate surfactant prod - get stiff lung due to dec compliance + high T
- problems: inc work of breathing due to red compliance + alveolar collapse + transudation due to high T
What is alveoli dependency?
joining of alveoli to each other to resist collapse + keep them open
When do abnormalities of lung compliance occur?
- when either lung parenchyma e.g. scarred in fibritic lung disease/alveolar lining fluid abnormal
List causes of low lung compliance
- lung fibrosis (scarred)
- neonatal resp distress syndrome
List causes of high lung compliance
emphysema (red quantity of lung tissue)
List obstructive lung diseases
- asthma
- chronic bronchitis
- COPD
List restrictive lung diseases
- lung fibrosis
- resp muscle weakness
- phrenic nerve damage
Describe normal resp system
- airways: normal - little to no R so air can flow in + out easily
- alveoli: normal gas exchange
- resp muscles: normal
- normal lung vol
- normal airflow rates
Describe how resp system affected in asthma
- airways: narrowed due to bronchoconstriction bc sm constricts in response to allergen
- mucosal oedema caused by inflamm
- alveoli: normal
- inc R to F due to dec V
Are effects of asthma rev or irrev?
rev as if take away trigger for bronchoconstriction - airway returns to normal
Describe how resp system affected in chronic bronchitis
airways: wall damaged by cig smoke
- hypertrophied glands + mucus prod
- alveoli normal
Describe how resp system affected in emphysema
- airways: poorly supported due to destruction of ISF + elastin
- inc compliance + flabby lung mean likely to collapse which leads to dynamic compression
- muscles: normal
What is overall effect of COPD?
narrow airways impede air flow
Describe how resp system affected in lung fibrosis
- airways: normal
- alveoli stiff due to fibrosis (scar tissue)
- resp muscles normal
- lung poorly compliant + need work to expand them
Describe how resp system affected in resp muscle weakness
- airways: normal
- alveoli: normal
- resp muscles: weak - can’t expand chest wall + therefore lung
How is airway + high airway R measured?
- airway R measured using body plethysmograph
- high airway R measured using forced exp manoeuvres
What are the forced exp manoeuvres + purpose?
- peak flow l.min-1
- forced exp vol vs time (FEV1, FVC)
- indirect assessment of airway R
What does peak flow measure?
measures peak exp flow rate (how quick blow into it)
How does airway obstruction affect peak flow?
causes low peak flow rate as have inc R to F in airways
