Gas Exchange

Question 1

What is pulmonary ventilation?

Answer 1

The volume of air breathed in and out per minute

PV = Tidal volume x Respiratory rate

Question 2

What is alveolar ventilation?

Answer 2

The volume of air exchanged between the atmosphere and alveoli per minute

Question 3

What does anatomical dead space refer to?

Answer 3

The inspired air that remains in the airways

Question 4

Why is alveolar ventilation less than pulmonary ventilation

Answer 4

Anatomical dead space

Question 5

To increase pulmonary ventilation both ____ and ____ must increase

Answer 5

Depth / Tidal Volume

Respiratory rate

Question 6

Is it more advantageous to increase the depth of breathing or respiratory rate in terms of increasing pulmonary ventilation; and why?

Answer 6

Depth

Because of dead space

Question 7

What is ventilation?

Answer 7

The rate at which gas is passing through the lungs

Question 8

What is perfusion?

Answer 8

The rate at which blood is passing through the lungs

Question 9

Does ventilation or blood flow vary from the top to the bottom of the lung?

Answer 9

Both

Question 10

What is the effect of variation in ventilation and blood from from the top to the bottom of the lung?

Answer 10

Partial arterial and alveolar pressure of oxygen are not the same (only significant difference in disease)

Question 11

Ventilated airways that are not adequately perfused are considered _____?

Answer 11

Dead space

Question 12

Do perfusion and ventilation always match?

Answer 12

No

Question 13

What are the mechanisms of ventilation perfusion matching?

Answer 13

Local controls that act on smooth muscles of airways and arterioles to match ventilation and perfusion

Question 14

What ventilation perfusion match response is initiated by increased CO2 levels in the alveoli?

Answer 14

Decreased airway resistance leading to increased airflow and subsequent increase in alveoli –> pulmonary vasodilation –> increased blood flow

Question 15

What is the physiological response to perfusion > ventilation in terms of blood flow?

Answer 15

Increased CO2 –> relaxation of smooth muscle in airway –> Dilation of local airways –> Decreased airway resistance –> increased airflow

Question 16

What is the physiological response to perfusion > ventilation in terms of small airflow?

Answer 16

Decreased oxygen –> increased contraction –> constriction of local blood vessel (vasoconstriction) / systemic arteriole vasodilation–> increased vascular resistance –> decreased blood flow

Question 17

What is the physiological response to perfusion < ventilation in terms of large airflow?

Answer 17

Decreased CO” –> contraction of smooth muscle in local airway –> constriction of local airways –> increased airway resistance –> decreased airflow

Question 18

What is the physiological response to perfusion < ventilation in terms of small blood flow?

Answer 18

Increased O2 –> relaxation of local pulmonary arteriolar smooth muscle –> vasodilation of local blood vessels / vasoconstriction of systemic arterioles –> decreased vascular resistance –> increased blood flow

Question 19

Which four factors influence the rate of gas exchange across the alveolar membrane?

Answer 19

1. Partial pressure of a gas
2. Surface area of alveolar membrane
3. Membrane Thickness
4. Diffusion coefficient

Question 20

What is the partial pressure of a gas?

Answer 20

The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature

Question 21

What is Dalton’s Law of Partial Pressures?

Answer 21

Total pressure exerted by a gaseous mix is the sum of the partial pressure

Question 22

How do you calculate the partial pressure of oxygen in alveolar air (PAO2) when oxygen is continuously diffuses from alveoli into the blood?

Answer 22

PAO2 = PiO2 - [PaCO2/0.8]

Question 23

What is the respiratory exchange ratio?

Answer 23

0.8

Question 24

What is PAO2?

Answer 24

Partial pressure of oxygen in alveolar air

Question 25

What is PiO2?

Answer 25

Partial pressure of oxygen in inspired air

Question 26

What is PaCO2?

Answer 26

The partial pressure of carbon dioxide in arterial blood

Question 27

Why is the carbon dioxide partial gradient greater than that of oxygen?

Answer 27

Because carbon dioxide is more soluble than oxygen

Question 28

What is the diffusion coefficient?

Answer 28

The solubility of gas in membranes

Question 29

Is the oxygen partial pressure gradient greater in systemic or pulmonary capillaries?

Answer 29

Systemic

Question 30

Where is the carbo dioxide partial pressure gradient the greatest?

Answer 30

Systemic capillaries

Question 31

What does a large gradient between alveolar and arterial partial carbon dioxide pressure indicate?

Answer 31

Problems with gas exchange or a right to left shunt in the heart

Question 32

What is Fick’s Law?

Answer 32

The amount of gas that moves across a sheet of tissue per unit of time is proportional to the area of the sheet but inversely proportional to its thickness

Question 33

How is the lungs surface adapted to facilitate effective gas exchange?

Answer 33

Very thin and large surface area + the airways divide repeatedly + very extensive pulmonary capillary network

Question 34

How are the respiratory membranes adapted for gas exchange?

Answer 34

Alveoli are thin-walled inflatable sacs with walls consisting of a single layer of flattened type I alveolar cells

Question 35

What are the non-respiratory functions of the respiratory system?

Answer 35

Remove/Modify/Activate/Inactivate various materials passing through pulmonary circulation
Route for water loss & heat elimination
Enables speech, singing & other vocalisations
Enhances venous return
Defends against inhaled foreign matter
Helps maintain normal acid-base balance
Nose serves as organ of smell