Equations/Laws

Question 1

Ohm’s Law

Answer 1

V= IR
voltage = current x resistance
For a given voltage, the current that flows is inversely proportional to the resistance

Power = current squared x resistance

Question 2

Alveolar gas equation

Answer 2

PAO2 = PiO2 - PACO2/RQ
PiO2 = FiO2(Patm - PH2O)
PAO2 = alveolar oxygen tension
Patm = atmospheric pressure 
PAH20 = SVP of H20 at body temp = 6.3kPa
PACO2 = alveolar carbon dioxide tension (=arterial CO2)
RQ = respiratory quotient (CO2 eliminated/O2 consumed) = 0.8 (carb 1.0, fat 0.7)

Question 3

Raoul’s Law

Answer 3

The depression of SVP of a solvent is proportional to the molar concentration of the solute present

Question 4

Shunt Equation

Answer 4

Qs/Qt
= (CcO2 - CaO2)/(CcO2 - CvO2)
Qs = shunt flow
Qt = total flow
CcO2 = pulmonary capillary oxygen content
CaO2 = arterial oxygen content
CvO2 = mixed venous oxygen content

Question 5

Oxygen content

Answer 5

CaO2
= (1.34 x Hb x SaO2)/100 + 0.023 x PaO2
1.34 = Hufner constant
0.023 = solubility coefficient for oxygen in blood at 37