ventilation and compliance Flashcards
anatomical dead space
~150ml
volume of gas occupied by conducting airways - so not available for gas exchange
tidal volume
volume of air breathed in or out lungs at each breath
expiratory reserve volume
max volume of air which can be expelled from lungs at end normal expiration
inspiratory reserve volume
max volume air which can be drawn into lungs at end normal inspiration
residual volume
volume of gas in lungs at end of maximal expiration
vital capacity
tidal volume + inspiratory reserve volume + expiratory reserve volume
total lung capacity
vital capacity + residual volume
inspiratory capacity
tidal volume + inspirtatory reserve volume
functional residual capacity
expiratory reserve volume + residual volume
FEV1
forced expired volume in one second
FEV1:FVC
fraction of forced vital capacity expired in one second
pulmonary ventilation
total air movement into/out of lungs
kind of insignificant
alveolar ventilation
fresh air getting to alveoli and available for gas exchange
partial pressure
pressure of gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multipled by pressure of the whole gaseous mixture
P02 and PCO2 during hyperventilation
increased alveolar ventilation
PO2 rises
PCO2 falls
P02 and PCO2 during hypoventilation
decreased alveolar ventilation
PO2 falls
PCO2 rises
type 1 alveolar cells
thin walled cell that permits gas exchange
type 2 alveolar cells
specialised cell that secretes surfactant
surfactant
detergent-like fluid produced by T2 cells
reduce surface tension on alveolar surface membrane thus reducing tendency for alveoli to collapse
what does surfactant do
increase lungs compliance
reduce lungs tendency to recoil
makes work breathing easier
when is surfactant most effective
small alveoli because surfactant molecules come closer together and so are more concentrated
when does surfactant production begin
what stimulates it
starts ~25wks gestation and completed ~36wks
stimulated by thyroid hormones and cortisol
compliance
change in volume relative to change in pressure
represents stretchability of lungs (not elasticity)
high compliance
large increase in lung volume for small decrease in ip pressure
low compliance
small increase in lung volume for large decrease in ip pressure
how does alveolar ventilation change from base to apex
alveolar ventilation declines with height from base to apex
how does compliance change from base to apex
compliance declines with height from base to apex
obstructive lung disease
obstruction of air flow, esp on expiration
restrictive lung disease
restriction of lung expansion
ex obstructive lung diseases
asthma
COPD
ex restrictive lung diseases
fibrosis
IRDS
oedema
pneumothorax
typical FEV1 value for fityoung male
4L
typical forced vital capacity value young fit male
5L
typical FEV1/FVC ration young fit male
80%
spirometry of ostructive lung disease
FEV1 down
ratio down
spirometry of restrictive lung disease
FEV1 and FVC down
ratio normal
