Gas Exchange and O2 Transport Flashcards
Surfactant is a lipid protein complex that is produced by…
Type II alveolar cells.
surfactant contains hydrophobic and hydrophilic regions that allow it to incorporate into air-liquid interface
Surfactant reduces ___ to a greater extent in smaller v. larger alveoli and prevents ___
surface tension; atelectasis = alveolar collapse
Surfactant reduces ___ which increases lung compliance and reduces ___
surface tension; inspiratory work
Surfactant reduces ___ which also reduces ___ in the alveoli
surface tension; fluid accumulation
Elastic Properties of the Lung
Inward elastic recoil facilitates exhalation
Elastic Properties of the Chest Wall
Outward elastic recoil facilitates inspiration
At volumes above functional residual capacity, the net recoil pressure of the respiratory system factors…
a decrease in lung volume
maintained by the actions of the muscles of inspiration
At lung volumes below functional residual capacity, the net recoil pressure of the respiratory system favors…
an increase in lung volume
maintained by the actions of the muscles of expiration
If intrapleural pressure is raised to atmospheric pressure (during puncture pneumothorax) the unopposed lung tissue will recoil ___ while the opposed chest wall will spring ___
inward; outward
This results in a collapsed lung
During a pneumothorax, the intrapleural pressure becomes the same as atmospheric pressure. as a result…
the lung collapses inward and the chest wall springs outward
Gas exchange at the capillaries occurs by
passive diffusion
Typical dry air contains ___ nitrogen and ___ oxygen and negligible amounts of CO2 and other gases. Combined, they exert the barometric pressure, which at sea level is 760mmHg.
79%; 21%
the partial pressure exerted by a gas is
directly proportional to the percentage of that gas in the total air mixture
Dalton’s Law
Px = Pb * Fx
Like any gas, water vapor exerts a partial pressure. At body temperature, the partial pressure of H2O vapor is
47mmHg
humidification of inspired air effectively dilutes the partial pressure of other inspired gases by 47mmHg
PIO2 =
(Pb - Ph20) * FO2
Ph2o = 47mmHg
FO2 = 21%
end tidal PO2 and PCO2 are good measures of
alveolar PAO2 and PACO2
towards the end of expiration, the air expired is alveolar air
PAO2 = PIO2 - PACO2 only works if…
O2 consumption = CO2 production
For a mixed diet, RQ is ___.
CO2 production =___ of O2 consumption
0.8; 80%
Alveolar Gas Equation
PAO2 = PIO2 - (PACO2/RQ)
an ___ relationship exists between PACO2 and alveolar ventilation
inverse
if ventilation doubles, the PACO2 will be ___ by ___
reduced by half
Gas Transfer across pulmonary capillaries
O2 partial pressure gradient from alveoli to blood = 60mmHg (100–>40)
CO2 partial pressure gradient from blood to alveoli = 6mmHg (46–>40)
Gas Transfer across Systemic Capillaries
O2 partial pressure gradient from blood to tissue cell = 60mmHg (100–>40)
CO2 partial pressure gradient from tissue cell to blood = 6mmHg (46–>40)
Rate of Gas Exchange Across Alveolar Membrane is dependent upon 4 things:
- Partial pressure gradients
- Surface area for diffusion: increase with exercise and decreases with emphysema and atelectasis
- solubility of gases
- thickness of alveolar membrane
Pneumonia
inflammatory fluid accumulation within alveoli
Pulmonary fibrosis
chronic airway irritation replaces lung tissues with fibrous tissue
Pulmonary Edema
increase in vascular permeability or pulmonary pressure (congestive heart failure), increases interstitial fluid
