Ventilation

Question 1

What are the 4 layers O2 has to cross to go from alveolar space to the hemoglobin?

Answer 1

1) Alveolar fluid, lining the alveolus and containing surfactant that re- duces its surface tension
2) The alveolar epithelium, composed of very thin epithelial cells and a basement membrane
3) A very thin interstitial space between the alveolar epithelium and the capillary membrane
4) The capillary endothelial membrane and its basement membrane

Question 2

Increasing alveolar fluid (pulmonary edema) will impede O2 transport across the membranes, but less so CO2. Why?

Answer 2

CO2 diffusion coefficient is 20X that of O2. It has significantly less work in crossing the membrane than does O2.

Question 3

What are the two types of V/Q mismatch?

Answer 3

1) Ventilation with no perfusion (ie. Alveolar dead space, such as in PE)
2) Perfusion with no ventilation (ie. Right to Left shunt, such as in pneumonia)

Question 4

What causes the oxyhemoglobin curve to shift?

(L shift causes increased SaO2 at lower PO2, but favors hemoglobin saturation of O2, and not tissues)

Answer 4

L shift: Alkalosis, Hypothermia, Hypocarbia, Carboxyhemoglobin/Methemoglobin

R shift: Acidosis, Hyperthermia, Hypercarbia,