Physics - Physiology principles

Question 1

Define fick principle

Answer 1

the quantity of substance entering a compartment in the inflowing blood must equal the sum of the accumulation in the compartment and the quantity leaving tin the efferent blood.

Question 2

What equipment is needed to accurately apply the fick equation

Answer 2

Pulmonary artery catheter and an arterial line in a peripheral artery.

Question 3

what measurements are rewired to derive the fick equaiton

Answer 3

oxygen uptake
mixed venous blood oxygen content
arterial blood oxygen content

Question 4

fick equation

Answer 4

VO2 = Q (Cao2 - CvO2)
Q = VO2/(Cao2 - CvO2)

Question 5

What does the fick equation assume (2)

Answer 5

constant flow (q)
CaO2 and CvO2 are constant
This is not accurate what approaching hypoxia or in variable cardiac output

Question 6

What other gas can be used for the fick equation, what are the issues?

Answer 6

CO2
CO2 varies much more with alveolar ventilation

Question 7

Shunt equation

Answer 7

QS/QT = (CvO2 - CaO2)/(CcO2 - CvO2)

Question 8

What information is needed for the shunt equation

Answer 8

Mix venous blood from a PAC
Pulmonary capillary content - derived from the alveolar gas equation
Arterial oxygen content - from art line

Question 9

What measurements are needed for dye dilution technique

Answer 9

mass of dye
dye concentration at time standard

Question 10

dye dilution formulae

Answer 10

(m) / AUC

Question 11

Thermodulition formulae

Answer 11

Q = [m(temperature change)]/AUC

Question 13

What is VCO2?

Answer 13

Production of CO2

VCO2 is the measure of carbon dioxide production in the body.

Question 14

What does the output of alveolar ventilation and the alveolar fraction of CO2 (FACO2) represent?

Answer 14

The product of VCO2

This relationship illustrates how CO2 levels are influenced by ventilation.

Question 15

How many outputs are there for O2 compared to CO2?

Answer 15

2 outputs for O2, 1 output for CO2

O2 has both uptake and expired gas outputs.

Question 16

What is the respiratory quotient (R)?

Answer 16

The ratio of CO2 production to O2 consumption

A typical value for R is 0.8.

Question 17

What is a typical value for R?

Answer 17

0.8

This implies VO2 = 250ml/min and VCO2 = 200ml.

Question 18

What happens if the values for PiO2, PaCO2, and R are very low?

Answer 18

It can give a negative value

This does not make sense as it relies on steady state conditions.

Question 19

What is PiO2?

Answer 19

Barometric pressure x FiO2

Fio2 x (Atmospheric pressure - saturated vapour pressure of water)

Question 20

What is the relationship between PAO2 and PiO2?

Answer 20

As pio2 increases as does pao2

Question 21

What is the effect of severe hypoventilation on PAO2?

Answer 21

It leads to hypoxia

This is particularly important in post-operative recovery.

Question 22

What does the equation Y = c - k/x represent?

Answer 22

A version of the Alveolar Gas Equation expressed in terms of alveolar ventilation

This illustrates the relationship between ventilation and PAO2.

Question 23

What happens to PAO2 with increased alveolar ventilation?

Answer 23

May provide little difference compared to increasing FiO2

This highlights the limited impact of ventilation on oxygen levels.

Question 24

What is the impact of hypoventilation on PAO2?

Answer 24

Rapid decline in PAO2

Emphasizes the critical need for oxygen in recovery settings.

Question 25

What is the input and output model for CO2?

Answer 25

The input is VCO2 (production of CO2) and the output is the product of alveolar ventilation and the alveolar fraction of CO2 (FACO2).

Question 26

What is the relationship between VCO2 and VO2?

Answer 26

The relationship is defined by the equation that connects CO2 production to O2 consumption.

Question 27

What variables alter the Alveolar Gas Equation (AGE)?

Answer 27

The variables are PiO2, PaCO2, and R (the respiratory quotient).

Question 28

What is PiO2?

Answer 28

PiO2 is calculated as Barometric pressure x FiO2.

Question 29

What is the typical value for the respiratory quotient (R)?

Answer 29

A typical value for R is 0.8, meaning VO2 = 250ml/min and VCO2 = 200ml.

Question 30

What happens when PIO2 is less than 8kPa?

Answer 30

There is a violation of the steady state condition.

Question 31

What is the effect of hypoventilation on PAO2?

Answer 31

Hypoventilation leads to a rapid decline in PAO2, emphasizing the importance of O2 in the recovery room post-anesthesia.

Question 32

What is Apnoeic Mass Transfer Oxygenation (AMTO)?

Answer 32

AMTO is a passive ventilation process where gas is drawn down the airway due to sub-atmospheric pressure.

Question 33

How long can PAO2 remain above 10kPa during apnoea?

Answer 33

If starting PAO2 is 80kPa and the reduction rate is 0.5kPa/min, it will take 140 minutes to fall below 10kPa.

Question 34

What factors determine the hypoxic threshold?

Answer 34

Factors include preoxygenation, FRC size, FiO2, VO2, and VCO2.

Question 35

What is the formula for nitrogen change during preoxygenation?

Answer 35

The formula is (Number of breaths / (Number of breaths + 1))^n.

Question 36

What does the constant 'e' represent in the context of preoxygenation?

Answer 36

The constant 'e' is approximately 0.3678.

Question 37

What is the wash-in function formula?

Answer 37

The wash-in function is represented by y = A(1-e^(-kt)).