Physiological Models

Question 1

What is fick principle

Answer 1

During any time interval, the quantity of substance entering a compartment must equal the sum of the accumulation in the compartment and the quantity leaving the efferemt blood

Question 2

VO2
VO2 with dot

Answer 2

Oxygen uptake
O2 uptake per minute

Question 3

Pulmonary blood flow (right ventricular cardiac output) equation

Answer 3

Q = VO2 / (CaO2 - CvO2)

Question 4

Dead space

Answer 4

Alveoli ventilated but not perfused therefore can’t take part in gas exchange

Question 5

Shunt

Answer 5

Alveoli perfused but not ventilated

Question 6

QT
QN
QS

Answer 6

QT = total cardiac output flow
QN = flow through normal alveoli
QS = flow through shunt alveoli

Question 7

Shunt equation (proportion of blood flow not being oxygenated due to unventilated alveoli)

Answer 7

Qs/ Qt = (CcO2 - CaO2) / (CcO2 - CvO2)

Question 8

CcO2

Answer 8

Efferent oxygen content from ideal alveoli. Estimated from PAO2 and HbO2 dissociation curve

Question 9

Thermodilution methodology and equation

Answer 9

Volume of cold saline injected and mixed with blood, resulting blood temperature measured by thermistor. Greater flow the less measured changed in blood temperature.

Q = m(change in temperature saline - change in temperature blood) / AUC

Question 10

Alveolar gas equation = alveolar ppO2

In steady state conditions

Answer 10

PAO2 = FiO2 - (PaCO2 / R)

Question 11

How does altering VA affect PAO2?

What is the relationship between VA and PAO2 for a fixed FiO2?

Answer 11

Doubling VA leads to small increase in PAO2.
Hypoventilation leads to rapid decline in PAO2 if no O2 added.