Week 3

Question 1

Henry’s Law

Answer 1

“at constant temperature, the amount
of gas dissolved in a liquid is directly proportional to the partial pressure of that gas at equilibrium above the gasliquid interface”

p = k * c

Where p is the partial pressure of the solute above the solution, k is Henry’s constant, and c is the concentration of the solute in the solution

increased delivery of oxygen (FiO2) to patients to improve arterial oxygenation (PaO2) and overpressuring (high concentration) anesthetics reflect the direct relationship of pressure and solubility described by Henry’s Law.

Increasing the partial pressure of a gas above a liquid will increase the amount of gas that dissolves in the liquid.

Henry’s law states that the amount of a gas that dissolves in a liquid is proportional to the partial pressure of the gas in the gas phase.

 The main applications of Henry’s law in anesthesia pertains to calculating how much O2 dissolves in blood and how much CO2 dissolves in blood.

Question 2

What is the solubility coefficient of O2 (aO2) and CO2

Answer 2

Solubility coefficient of O2 (aO2) and CO2 (aCO2) in blood:
 aO2 = 0.003 ml /100 ml blood/ mmHg of O2
 aCO2 = 0.067 ml/ 100 ml blood/ mmHg of CO2

If the oxygen partial pressure in arterial blood increasesd from 50 o 350, the amount of dissolved oxygen increases by how much?

Dissolved O2 with PaO2 at 50mmHg= 0.003 x 50=0.15 ml O2/100 ml blood

Dissolved O2 with 350 = 0.003 X 350= 1.05

1.05-0.15= 0.90