19. mechanics of breathing Flashcards
(32 cards)
what are two forces that provide resistance to breathing
lung compliance- the ease with which the lungs can be expanded
airway resistance
what affects compliance (3)
elasticity of lung tissue-connective tissue structure
mobility of chest wall/ thoracic cage
surface tension
does elastic recoil (returning to normal shape) of the lung aid or oppose inspiration
opposes inspiration, aids expiration
airway resistance
if the diameter of the bronchiole is affect, opposes both inspiration and expiration
formula for compliance
change in volume / change in pressure
what is surface tension caused by
intermolecular forces between molecules in a liquid
thin fluid layer between alveolar cells and the air is being stretched
what equation links pressure, surface tension and the radius of an alveolus together
P=2T/r
what is Laplaces law
at equilibrium the tendency of increased pressure to expand the alveolus balances the tendency of surface tension to collapse it
what is the function of pulmonary surfactant
reduces the surface tension increasing compliance
equalises the pressure differences between small sized and large sized alveoli so both can expand and contract easily
surfactant help to keep uniform alveolar size. it is more concentrated in ______ alveoli
smaller
lower surface tension means easier to inflate smaller alveoli
neonatal respiratory distress syndrome
lack of surfactant secretion in premature babies, which results in reduced compliance and alveoli collapse upon exhalation
it is also difficult to inflate the lungs
factors affecting airway resistance (2)
lung volume-bronchi dilate as lungs expand
bronchial smooth muscle
bronchoconstriction-parasympathetic nerves
bronchodilation-sympathetic nerves and adrenaline
what stimuli causes reflex bronchoconstriction
smoke dust irritants
histamine (allergic response)
how can we measure airway resistance
FEV1 / FVC x 100
what is FVC
forcibly breathing out vital capacity
what is FEV1
forced expiratory volume in one second
breath sounds can tell us
the presence of mucus/fluid
if no breath sounds, collapsed lung?
what does a peak flow meter do
measure the speed at which you breathe out
how can we measure lung volumes and capacities
a spirometer
what is the tidal volume TV
the volume of air inhaled or exhaled in one quiet breath
residual volume RV
is the volume of air left in the lungs after a normal passive exhalation
expiratory reserve volume ERV
the amount of air that can be forcibly exhaled after a normal tidal volume exhalation
inspiratory reserve volume IRV
amount of air that can be forcibly inhaled after a normal tidal volume inhalation
vital capacity VC
the maximum amount of air that can be expired after a maximum inspiratory effort
VC=TV + IRV + ERV
