Question

At sea level, the red blood cell is fully oxygenated (meaning near alveolar values) by (\sim 0.2 ) seconds when traversing through a pulmonary capillary. At extreme altitude, the red blood cell is not fully oxygenated by the time it reaches the end of a capillary. This is due to:

(a) The increased CO2 in the alveolar space
(b) The reduced alveolar PO2 driving force
(c) The longer transit times through the pulmonary capillary
(d) All of the above

Answer 1

Red blood cells are not fully oxygenated at extreme altitudes due to a reduced alveolar PO2 driving force, longer transit times through the pulmonary capillary, and increased levels of carbon dioxide in the alveolar space.

Step-by-step explanation:

The reason why red blood cells are not fully oxygenated at extreme altitudes is due to multiple factors. One factor is the reduced alveolar PO2 driving force. At high altitudes, the partial pressure of oxygen (PO2) in the alveoli is lower compared to sea level. This smaller difference in partial pressures between the alveoli and the blood reduces the amount of oxygen that crosses the respiratory membrane and binds to hemoglobin in the red blood cells. Another contributing factor is the longer transit times through the pulmonary capillary. When red blood cells spend more time in the capillaries, there is less opportunity for oxygen to bind to hemoglobin. Finally, the increased levels of carbon dioxide (CO2) in the alveolar space can also hinder full oxygenation of red blood cells.