Lecture 26 Flashcards
Gas Composition and Exchange
The 3 components of air
78% N2, 21% O2, 0.033% CO2
What is Daltons Law
total pressure is the sum of all the gasses individually extorted pressures
total air pressure
Patm= PN2 + PO2 + PCO2
humid air
Patm =PN2 +PO2 +PCO2 +PH20
Gas composition in the alveoli
100 mmHg of O2
40 mmHg of CO2
Gas composition in the atmosphere
160 mmHg PO2
0.25mm Hg PCO2
When alveolar ventilation increases
alveolar PO2 increases and PCO2 deceases
What is increased alveolar ventilation called?
Hyperventilation
what is decreased alveolar ventilation called?
Hypoventilation
Rate of diffusion is proportional to…
- Surface area (A)
- Membrane Permeability (D = diffusion constant)
- Concentration (Partial Pressure) gradient
Rate of diffusion is inversely proportional to…
– Diffusion distance (T)
* Membrane thickness
* Interstitial fluid
what is the diffusion rate formula?
Diffusion rate = A x D x (change of Pgas) / T2
The partial pressures in Pulmonary Circulation
Alveolar PO2 > Venous Blood PO2
Alveolar PCO2 < Venous Blood PCO2
The partial pressures in Systemic Circulation
Arterial PO2 > Tissue PO2
Arterial PCO2 < Tissue PCO2
Factors that decrease oxygen reaching the alveoli
Low oxygen content in the atmosphere
Low Alveolar Ventilation
– Decreased lung compliance (how easily they can expand)
– Increased airway resistance – CNS depression (drugs,
alcohol overdose)
