Mechanism of ventilation pt.2

Question 1

What determines VC

Answer 1

Strength of respiratory muscles
Elastic resistance of lungs

Question 2

What affects VC

Answer 2

Gender, age, body build and posture

Question 3

What is the ratio of FEV1/FVC of normally pulmonary function

Answer 3

0.8/ 80%

Question 4

What is the main problem with acute obstructive disease, give an example

Answer 4

Increased airway resistance
Bronchial asthma

Question 5

What is the main problem with chronic obstructive disease, give an example

Answer 5

decreased elasticity
Emphysema

Question 6

What is the main problem with obstructive lung diease

Answer 6

Difficulty exhalation

Question 7

What is the main problem with restrictive lung disease, give an example

Answer 7

Difficulty inhalation
pulmonary fibrosis

Question 8

Which one has much reduced FVC, why

Answer 8

Restrictive lung disease
Lungs don’t stretch as much -> less air is inhaled -> lower FVC

Question 9

which one has much reduced FEV1, why

Answer 9

Obstructive lung disease
Poor elastic recoil -> difficult to exhale quickly

Question 10

which has lower and which has higher FEV1/FVC

Answer 10

Lower: Obstructive lung disease
higher: Restrictive lung disease

Question 11

Spirometry Findings in obstructive vs Restrictive
RV
FRC
TLC
VC
FVC
FEV1
FEV1/FVC

Answer 11

Obstructive
RV: higher
FRC: higher
TLC: higher
VC: lower
FVC: lower
FEV1: much lower
FEV1/FVC: much lower (hallmark)

Restrictive:
RV: lower
FRC: lower
TLC: lower (hallmark)
VC: lower
FVC: lower
FEV1: much lower
FEV1/FVC: much lower (hallmark)

Question 12

What is pulmonary ventilation

Answer 12

The volume of air that flows into and out of the respiratory track/ minute

Question 13

How to calculate it

Answer 13

Tidal volume x breaths per minute

Question 14

what is dead space

Answer 14

Part of the respiratory system where no gas echange takes place

Question 15

what is the function of dead space

Answer 15

Warms, Humidifies and purifies air

Question 16

what is the value of dead space

Answer 16

150 cm³ (⅓ TV)

Question 17

What causes alveolar dead space

Answer 17

Non functioning/ dead alveoli
Non perfused alveoli (embolism or thrombus in pulmonary capillary)

Question 18

In normal lungs ??=??

Answer 18

Physiological d.s = Anatomical d.s

Question 19

in diseased lung ??>??

Answer 19

Physiological d.s (e.g. damaged alveoli) > anatomical d.s

Question 20

what are the factors affecting anatomical dead space

Answer 20

Physiological: Large body size/ weight/ upright position/ neck extension

Bronchodilatation: By β-adrenergic/ anticholinergic drugs

Breathing through artificial airways: increases anatomical d.s -> less volume reaching the lungs

Question 21

What is the significance of dead space

Answer 21

Difference in composition between alveolar and expired air
Difference between pulmonary ventilation and alveolar ventilation

Question 21

How to calculate anatomical dead space

Answer 21

body weight in lbs
kg= 2.2 lbs

Question 22

What is the significance of dead space

Answer 22

Difference in composition between alveolar air and expired air
Difference between pulmonary ventilation and alveolar ventilation

Question 23

How to calculate dead space ventilation (VD)

Answer 23

dead space volume x respiratory rate

Question 24

How to calculate alveolar ventilation

Answer 24

Pulmonary ventilation (VE) - dead space ventilation (VD)
OR
(TV-DS) x respiratory rate

Question 25

Which is more beneficial, doubling tidal volume or respiratory rate

Answer 25

Doubling tidal volume

Question 26

Which is more beneficial, shallow rapid or slow deep breathing

Answer 26

Slow deep breathing

Question 27

What does hyper/ hypo ventilation apply to

Answer 27

Alveolar ventilation

Question 28

How does hypoventilation affect alveolar PCO₂ and why

Answer 28

Increases it as less air is expired out

Question 29

How does hyperventilation affect alveolar PCO₂ and why

Answer 29

Decreases it as more air is expired out

Question 30

how to calculate VA using VCO₂ and PACO₂

Answer 30

VA = (VCO₂ / PACO₂) x constant (0.863 if mmgH or 115.1 if pKa)