Diffusion of gas in the respiratory membrane
The rate of diffusion of gas across the respiratory membrane is
-        Directly proportional to 

The pressure gradient across the membrane
Lipid solubility of the gas 
The surface area of the membrane

-        Inversely proportional to

The thickness of the membrane​
The molecular weight of the gas
Directly proportional to thickness of respiratory membrane
Inversely proportional to molecular weight of the gas
No lipid - water solubility
Inversely proportional to pressure gradient