Lecture 23: Hyperbaric Chamber, Iron Lung, V/Q Mismatch (Final Exam)

Question 1

What benefits/treatments are hyperbaric chambers utilized for?

Answer 1

• Decompression Treatment
• Wound healing (↑PO₂ to be able to reach poorly perfusing wound)
• Leukemia/cancer treatment

Question 2

What atm capability do hospital hyperbaric chamber’s have?

Answer 2

3 atm

Question 3

What gasses are toxic when administered in vast excess?

Answer 3

All of them (CO₂, N₂, O₂ ,etc)

Question 4

What is the reason for the change in PO₂ between the blue and red lines?

Answer 4

Higher dissolved O₂ in the blue line due to increased pressure. Red line has maxed out “dissolvability”.

Question 5

What conditions would ensure oxygen toxicity?

Answer 5

PaO₂ ≥ 4 atms @ 100% O₂

Question 6

What are free radicals?

Answer 6

ROS (reactive oxygen species) are oxygen containing molecules that are used to break down other molecules.

Question 7

Name the pertinent ROS.

Answer 7

O₂⁻ (superoxide)
OONO⁻ (Peroxynitrite)
H₂O₂ (Peroxide)
NO (Nitric Oxide)

Question 8

Is O₂ typically charged or uncharged? What occurs if it becomes negatively charged?

Answer 8

• Uncharged
• If negatively charged, becomes highly reactive.

Question 9

Why do we not like to combine high levels of O₂ administration with NO administration?

Answer 9

NO + O₂⁻ = OONO⁻

Question 10

Why is peroxynitrite so dangerous?

Answer 10

OONO⁻ will destroy DNA and proteins

Question 11

What enzyme gets rid of O₂⁻ ?

Answer 11

superoxide dismutase

Question 12

What enzymes control the quantity of oxygen free radicals?

Answer 12

Superoxide dismutase
Peroxidase
Catalase
Acetylcysteine

Question 13

What free radical “scavenger” can be given to reduce ROS ?

Answer 13

NAC = N-acetylcysteine

Good for hangovers too!

Question 14

What will overwhelm our body’s free radical enzymes?

Answer 14

Excessive O₂

Question 15

What enzyme breaks down H₂O₂ ?

Answer 15

Peroxidase

Question 16

Describe a reperfusion injury.

Answer 16

Tissue over-perfuses area of previous ischemia → increased vessel diameter and O₂ oversupply

Question 17

What produces the negative pressure of an iron lung?
Why is negative pressure beneficial?

Answer 17

• Leather diaphragm pulled via a motor
• Negative pressure from iron lung is similar to natural inspiration and is less traumatic on the cardiopulmonary system over long periods of time.

Question 18

Which of the following would be indicative of negative pressure breathing?
What about positive pressure ventilation?

Answer 18

A. Alveoli are more opened up especially to the periphery.
B. PPV due to alveoli being “squished” closer to the chest wall.

Question 19

What would be necessary to analyze the amount of volatile anesthetic or O₂ in the same way we analyze end-tidal CO₂ ?

Answer 19

Mass spectrometry

Question 20

What occurs with our A-a gradient as we get older, Stephen?

Answer 20

Older = ↑V_D & ↑ shunting = ↑ A-a gradient

Question 21

How might we estimate a normal A-a gradient?

Answer 21

A-a gradient = (Age + 10) ÷ 4

Question 22

What would be the estimated A-a gradient of a 50 year old?

Answer 22

(50 + 10) ÷ 4 = 15mmHg

Question 23

What is R?
What is a normal R value?

Answer 23

R = RER (Respiratory Exchange Ratio)
R = 0.8 normally

Question 24

What is the alveolar gas equation?

Answer 24

P_AO₂ = [(P_B - 47mmHg) x FiO₂] - (PaCO₂ ÷ R)

Question 25

How is R calculated?

Answer 25

CO₂ production ÷ O₂ production

200 mLCO₂ ÷ 250 mLO₂ = 0.8

Question 26

What would increase your RER?

Answer 26

↑ carbohydrate intake = ↑ CO₂ production = ↑R

Question 27

What would decrease your RER?

Answer 27

↑ fat intake = ↓CO₂ production = ↓R

Question 28

What diet would be preferred for a COPD patient?
Why?

Answer 28

• High fat, low carb
• Decreased CO₂ production and thus less respiratory workload.

Question 29

At what P_ACO₂ would one expect to start seeing CNS toxicity?

Answer 29

≥ 80 mmHg

Question 30

Calculate P_AO₂ for someone with the following parameters.

PaCO₂ = 50 mmHg
ΔCO₂ =225 mLCO₂
ΔO₂ = 250 mLCO₂
FiO₂ = 21%

Answer 30

R = ΔCO₂ ÷ ΔO₂
R = 225 ÷ 250 = 0.9

P_AO₂ = [(P_B - 47mmHg) x FiO₂] - (PaCO₂ ÷ R)

P_AO₂ = [(760 - 47) x 0.21] - (50 ÷ 0.9)

P_AO₂ = 94.17 mmHg

Question 31

If V_A = 3.5L and Q = 5L what would you anticipate is occurring?

Answer 31

3.5 ÷ 5 = V/Q = 0.7

Shunting

Question 32

If V_A = 4.2L and Q = 4.2L what would you anticipate is occurring?

Answer 32

4.2 ÷ 4.2 = V/Q = 1.0

Dead space

Question 33

If one had a completely blocked airway, what would the V/Q be?
What P_ACO₂ and P_AO₂ would you expect?

Answer 33

• V/Q = 0/5 = 0 (Shunt)
• P_AO₂ = 40mmHg
• P_ACO₂ = 45mmHg

Question 34

If one had a completely blocked vasculature, what would the V/Q be?
What P_ACO₂ and P_AO₂ would you expect?

Answer 34

• V/Q = 4.2/0 = ∞ (dead space)
• P_AO₂ = 150mmHg
• P_ACO₂ = 0mmHg

Question 35

Apical alveoli are typically _______, whilst basal alveoli are typically _______.

Answer 35

larger; smaller

Question 36

Apical vessels are typically _______, whilst basal vessels are typically _______.

Answer 36

smaller; larger

Question 37

At what rib number would one expect V/Q differences between the base and apex of the lungs to equalize?

Answer 37

~ Rib 3

Question 38

What P_AO₂ and P_ACO₂ would you expect looking at the apex of the lung?

Answer 38

• P_AO₂ = 130mmHg
• P_ACO₂ = 30 mmHg

Question 39

What P_AO₂ and P_ACO₂ would you expect looking at the base of the lung?

Answer 39

• P_AO₂ = 90 mmHg
• P_ACO₂ = 42 mmHg

Question 40

How could emphysema change a normal capnograph?
Why would this occur?

Answer 40

• Capnography plateau would be inverted.
• Due to air initially coming from the base, which then collapses, causing air to come from the less CO₂ filled apex.