Question

If a person has a disease that causes fluid build up in the extra cellular fluid, how would that affect the diffusion of oxygen and carbon dioxide into and out of the extra cellular fluid from the alveoli?
Would they (O2 and CO2) be affected equally?
Why or why not?
How could a disease that causes this symptom be caused?
What would happen to the pH of the plasma?
Why?
How might the kidneys try to compensate?

Answer 1

Due to an increase in fluid in the extracellular compartment, Interstitial fluid level would be decreased that makes the respiratory membrane thicker and hence diffusion will be difficult.

  Diffusion of carbon dioxide will be more difficult as the pressure gradient for CO2 is less compared to Oxygen. This will result in accumulation of CO2 in the blood leading to lowering of pH.

The disease that might cause accumulation of fluid in the extracellular fluid might be the infection, and damage to the alveolar epithelium as occurs in emphysema.

The lowering of pH due to accumulation of CO2 occurs because CO2 combines with water to form H+ and bicarbonate AT TISSUE LEVEL, resulting in acidosis.

Kidney compensate this respiratory acidosis by allowing increased reabsorption of bicabonate and excretion of H+ ion.