Lecture 15 - Ventilation

Question 1

Assertion question: FEV1/FVC ratio does not decrease below 70% in restrictive lung disease BECAUSE restrictive lung disease does not affect the airway resistance

Answer 1

A. Both statements (the one before and the one after “BECAUSE”) are true, and are causally related (the
fact presented in the first statement is a result of the fact presented in the second statement).

Question 2

What do forced breathing measurements give us?

Answer 2

Info about air flow rates

Question 3

What is forced vital capacity (FVC)?

Answer 3

maximum breath into maximum breath out (VC) - forced out as hard as possible
Variant of vital capacity (VC), useful diagnostic tool for the diagnosis of lung diseases – indicator of airway resistance

Question 4

What is FEV1?

Answer 4

Forced expiratory volume in one second

Question 5

What are the air flow rates in healthy lungs?

Answer 5

In healthy lungs -FEV1 / FVC = ~80%, (80% expirated in 1 second)

Question 6

What happens to air flow rates in obstructive lung disease?

Answer 6

FEV1 big decrease & FVC decrease, thus FEV1/FVC = decrease
Ratio of less than 70%, indicative of increased airway resistance

Question 7

What happens to air flow rates in restrictive lung disease?

Answer 7

FEV1/FVC ratio doesn’t change (or increased) - no change in airway resistance

Question 8

What airway resistance disease affects air flow rates?

Answer 8

Obstructive lung disease

Question 9

How can we measure total (mouth) ventilation (V̇E)?

Answer 9

Total (mouth) ventilation (V̇E)= frequency (f) x tidal volume (VT)

Question 10

When can change V̇E?

Answer 10

To match metabolic demands (involuntarily, e.g exercise)
Voluntarily (changing breathing behaviour)

Question 11

What is dead space?

Answer 11

Some of the inhaled air never gets to the alveoli
so cannot gas exchange – known as dead space
ventilation ( VD )

Question 12

What are the two types of dead space that contribute to VD?

Answer 12

1. Anatomical dead space
2. Physiological dead space
   VD = anatomical dead space + functional dead space

Question 13

Where and what is our anatomical ‘dead space’?

Answer 13

Conducting airways (including mouth, trachea)
Ventilated but no respiration (no gas exchange)

Question 14

Where and what is our functional ‘dead space’?

Answer 14

Respiratory area (gas exchange) could exchange gases but not happening - unused respiratory area

Question 15

How big is dead space?

Answer 15

Dead space is approximately 1/3rd of the inspired air.
Dead space (VD) is approx. = 150 ml
145 ml air will stay in mouth,
trachea and Airways - 145 ml not available for respiration 355 ml air get into the respiratory area - approx. 5 ml of this air is not available for gas exchange

Question 16

How can VD determine VA?

Answer 16

VE = VD + VA

Question 17

How does Pulmonary Fibrosis affect VD?

Answer 17

Increases dead space by transforming
respiratory tissue into fibrotic tissue (e.g. cystic fibrosis, pulmonary fibrosis)
Scared alveoli that don’t work

Question 18

How does Pulmonary Hypertension affect VD?

Answer 18

Increased dead space by impairing pulmonary
perfusion (pulmonary arteries not functioning properly)

Question 19

What is the affect of fast shallow breathing on VA?

Answer 19

Decreased AV – causing hypoxia (↓PAO2), hypercapnia (↑PACO2) and acidity
From a gas exchange point of view, wastes ventilation in the dead space
Is energetically costly for the respiratory muscles
Less gas exchange (when the tidal volume (VT) is low)

Question 20

What is the affect of slow deep breathing on VA?

Answer 20

Increased alveolar ventilation – causing hyperoxia (↑PAO2), hypocapnia (↓PACO2) and
alkalinity
↑ Gas exchange
Is energetically costly for the respiratory muscles

Question 21

What is Dalton’s Law?

Answer 21

Partial Pressure = fraction of individual gas x total gas pressure
Pgas= Fgas X Ptotal

Question 22

What is partial pressure (P)?

Answer 22

In a gas mixture (air), each gas exerts its own individual pressure, called a partial pressure (P), in direct proportion to its fractional concentration in the mixture.

Question 23

What is alveolar ventilation in a healthy lung?

Answer 23

4 L/min

Question 24

What is Pulmonary blood blow in a healthy lung?

Answer 24

5 L/min

Question 25

What is the ventilation and perfusion relationship defined by?

Answer 25

Defined as the ratio of ventilation to perfusion
Normal = 0.8
Any change in the ratio – impairs O2 and CO2
transfer

Question 25

What is the ventilation and perfusion relationship defined by?

Answer 25

Defined as the ratio of ventilation to perfusion
Normal = 0.8
Any change in the ratio – impairs O2 and CO2
transfer

Question 26

What happens to ventilation and perfusion relationship during physiological shunt?

Answer 26

Ratio does not = 0.8
Decreased ventilation
Constant perfusion

Question 27

What happens to ventilation and perfusion relationship during anatomical shunt?

Answer 27

Ratio does not = 0.8

Question 28

What happens to ventilation and perfusion relationship during Low ventilation/perfusion?

Answer 28

Ratio does not = 0.8
Decreased ventilation
Constant perfusion

Question 29

What lung diseases impair ventilation?

Answer 29

• Atelectasis (fibrosis)
• Emphysema
• Pulmonary oedema (fluid)

Question 30

What lung diseases impair perfusion?

Answer 30

• Pulmonary hypertension
• Heart failure
• Vascular disease associated with COPD