lung mechanics Flashcards
define obstructive lung disease and its characteristics
the flow of air into and out of the lung is obstructed
lungs are operating at higher volumes
chronic causes: COPD, emphysema
acute causes: asthma
define restrictive lung disease and its characteristics
inflation/deflation of the lung or chest all is restricted
lungs are operating at lower volumes
pulmonary causes: lung fibrosis, interstitial lung disease
extrapulmonary causes: obesity and neuromuscular disease
volume pressure graph
what happens at the top right
and what happens at the bottom left
top right: muscle force pushing outwards
bottom left: muscle force pushing inwards
what happens to the line in the volume pressure graph with regards to obstructive and restrictive diseases
obstructive- line is higher
restrictive- line is lower
define compliance and equation
tendency to distort under pressure
compliance = delta V/ delta P
define elastance and equation
tendency to recoil to its original volume
elastance = delta P/ delta V
why are fluid filled lungs more compliant than airfilled lungs?
air water interface exhibits surface tension 77fluid water interface does not
law of Laplace
P = (2T)/ r
components of pulmonary surfactant
80% polar phospholipids
10% non polar lipids
10% proteins
purpose of surfactant
prevents collapse of small alveoli
increases compliance (by reducing surface tension)
reduces the ‘work of breathing’
relationship between conductance and resistance
airways are not rigid pipes- they dilate as long volume increases
the ‘conductivity’ of the airways increases with increasing volume
(as resistance decreases)
why are large airways supported with cartilage
due to hard expiration
otherwise they would collapse
