Respiratory physiology Flashcards
ideal gas law
(Pb - Ph2o) x V = M x R x T
lung volumes
- residual volume - 1.5L
- expiratory reserve volume - 1.5L
- tidal volume - 0.5L
- inspiratory reserve volume - 2.5L
transmural pressure
Ptm = Pi - Po
lung capacities
- functional residual capacity (FRC)
- inspiratory capacity
- vital capacity
- total lung capacity
limiting ability of lung and chest wall
lung - limit expansion (inspiration)
chest wall - limit constriction (expiration)
sum of compliance
1/C(RS) = 1/C(L) + 1/C(CW)
pleural pressure
-6 cm H2O
effect of emphysema and fibrosis on lung compliance
emphysema increase lung compliance
fibrosis decrease lung compliance
interdependence of alveoli
one alveolus reduce volume, surr. alveoli expand
recoil force
surface tension
water molecule on surface - unequal pulling force - tension
keep air-fluid surface as small as possible
laplace law
P = 2(ST/r) ST = surface tension r = radius
surfactant
hydrophobic tail pulled toward air side of the air-fluid border - equalized force - reduce surface tension
90% lipid
10% protein
protein - albumin, IgA, SP-A, B, C, D
SP-A
important in exerting feedback control that limit the surfactant secretion
alveolar radius and surfactant
- alveolar radius increase - surfactant thinner - surface tension increase
- alveolar radius decrease, surfactant thicker - surface tension decrease
surfactant deficiency
- glucocorticoids - stimulate surfactant production
- Infant Respiratory Distress Syndrome - IRDS - artificial surfactant given
surfactant production
alveolar type II
surfactant clearance
alveolar macrophage degrade surfactant
type II cell recycle or destroy the rest
hagen-poiseuille law
Q = (delta)P / R
silent lung disease
airway resistance of lower airway very low compared to the upper airway, obstructive disease in the lower air way do not display obstructive airway symptoms
factors affecting airway resistance
- density and viscosity of the inspired gas
- reduction in Pco2
- sympathetic and parasympathetic innervation and transmitters
- agents : histamine, acetylcholine, thromboxane A2, prostaglandin F2, and leukotrienes LTB4, C4 and D4
- lung volume
effect of reduction in PCO2
bronchoconstriction
- local hyperventilation -> reduction in PCO2 -> R(aw) increase -> divert the ventilation
bronchocontricting agent
histamine
thromboxane A2
prostaglandin F2
effect on lung volume on airway resistance
increase in lung volume -> decrease in airway resistance 6
FRC - R(aw) = 1.3cm H2O x I^-1 x s
beta2-adrenergic agonist
airway resistance reduced
forced expiration (4 compo)
- forced expiratory volumin in 1 sec (FEV1)
- forced vital capacity (FVC)
- Ratio (FEV1/FVC) - normal 80%
- peak expiratory flow rate (PEFR)
normal, obstructive, restrictive FEV1/FVC ratio
normal - 80%
obstructive - 42%
restrictive 90%
high volume of lung - high alveolar pressure
This is due to
increased recoil force of alveoli
better alignment of resp muscle
effort dependant region
bfore FEF 50%
graph change upon the patient’s effort
effort independant region
after FEF 50%
graph does not change upon patient’s effort
obstructive diesase
Residual volume increase
TLC increase
high resistance
restrictive disease
Residual volume and TLC both decrease proportionally
decreased lung volume
flow/volume curve - plateau
obstruction in extrathoracic airway
flow/volume curve - sharp drop
obstruction in intrathoracic airway
obstructive pulmonary disease
chronic bronchitis, emphysema, asthma
restrictive pulmonary disease
pulmonary fibrosis
compliance
change in volume / transmural pressure
transpural pressure for
lung = alveolar pressure - pleural pressure
chest wall = pleural pressure - outside pressure
alveolar membrane repair is done by…
type II alveolar cell
total ventilation, dead space ventilation, alveolar ventilation
toal vent = dead space vent + alveolar vent
normal total ventilation
8L/min
fraction of O2 in fresh air
21%
fraction of O2 in the used air
14%
calculation of dead space using Bohr equation
V(T) x F(E) = (V(T) - V(D)) x F(A) + V(D) x F(I)
basal metabolic rate - nomal range
VO2 250mL/min at 37C (98.6F) 275mL/min at 28C (100.6F) 225mL/min at 36C (96.6F) chnage 11% per 1C change BMR - not eveyday regular, but the minimum required (early morning, lying on the bed)
normal adult oxygen comsuption
280mL/min
can be 10X higher at VO2 max
normal adult CO2 production
250mL/min
respiratory exchange ratio
R = CO2/O2
Glucose R = 1
Fat R = 0.7
protein R = 0.8
RQ (tissue) and R (lung) relationship
RQ = R in steady state - pulmonary gas exchage match the needs of metabolism in the peirpheral tissue
deviate during exercies, crying, breath holding, hyperventilation, hypoventilation
Dalton’s law
P(total) = P1 + P2 + P3
sum of partial pressures = total pressure
partial pressure of a gas X
Px = Fx x (P(B) - P(H2O))
Px x V = Mx x R x T
P(B) - P(H2O)) x V = M x R x T (sum of dry gases
inspired PO2 calculation
P(IO2) = F(IO2) x (P(B) - P(H2O))
IO2 = inspired O2 P(B) = 747 for sea level (usually 760), 347 for 20,000 feet, 247 for 29,035 feet (Mt. Everest) P(H2O) = 47mmHg - constant through different altitudes F(IO2) = .21 - can change by breathing supplmental O2
alveolar PO2 (P(A)O2) calculation
P(A)O2 = P(I)O2 - (P(A)CO2 / R)
P(A)CO2 = usually 40mmHg