Ventilation

Question 1

What does “volume” refer to

Answer 1

discrete sections of a lung volume graph that do not overlap

Question 2

What is capacity

Answer 2

the sum of two or more volumes

Question 3

What can vital capacity be thought of as

Answer 3

useful air

Question 4

What is tidal volume

Answer 4

normal breathing at rest

Question 5

What is the residual volume

Answer 5

volume that is not expelled in ventilation to allow the lungs to inflate again as wet surface will stick together

Question 6

What factors affect volumes and capacities

Answer 6

Sex
Disease
Body size
Fitness
Age

Question 7

Define anatomical dead space

Answer 7

The capacity of the airways incapable of undertaking gas exchange

Question 8

Define alveolar dead space

Answer 8

Capacity of the airways that should be able to undertake gas exchange but cannot e.g. hypoperfused alveoli

Question 9

Define physiological dead space

Answer 9

Equivalent to the sum of alveolar and anatomical dead space

conducting zone + non-perfuse parenchyma air

Question 10

Describe the respiratory zone

Answer 10

7 generations
Gas exchange
350mL
air here is equivalent to alveolar ventilation

Question 11

Describe the conducting zone

Answer 11

16 generations
No gas exchange
140mL
equivalent to anatomical dead space

Question 12

Describe non-perfuse parenchyma

Answer 12

alveoli with no blood supply
No gas exchange
0mL
alveolar dead space

Question 13

Give 2 reversible procedures to alter the dead space

Answer 13

Tracheostomy or cricothyrotomy to decrease dead space

Anaesthetic circuit or snorkelling to increase dead space

Question 14

How does changes in pressure alter the work that must be put in for inflation

Answer 14

The greater the pressure, the more work that must be put in to expand the lungs

Question 15

Describe what occurs during ventilation in terms of dead space

Answer 15

1. Functional residual capacity initially
2. Alveolar pressure inside decreases
3. Air flows in due to gradient
4. Tidal volume reached
5. Lungs recoil and the air is compressed
6. Pressure gradient forces air out
7. Ends at functional residual capacity

Question 16

Define pulmonary ventilation

Answer 16

Air ventilating the entire airway

Question 17

Define alveolar ventilation

Answer 17

air ventilation the respiratory exchange surface

Question 18

When is ventilation +ve or -ve pressure

Answer 18

\+ve= ventilation or CPR
-ve = normal breathing

Question 19

Describe the healthy chest

Answer 19

Single unit

Pleural cavity is a partial vacuum

Question 20

Describe tidal breathing

Answer 20

Tidal breathing is predominantly diaphragm-induced

Maximum ventilation involves full inspiratory muscle recruitment

Question 21

Describe the chest wall relationship

Answer 21

The chest wall has a tendency to spring outwards and the lung has a tendency to recoil inwards
These forces are in equilibrium at end-tidal expiration (functional residual capacity, FCR) which is the neutral position of the intact chest

Question 22

What leads to inspiration and expiration in terms of the chest wall relationship

Answer 22

inspiratory muscle effort and chest recoil > lung recoil = inspiration
chest recoil expiration

Question 23

Describe the membranes surrounding the lung

Answer 23

The lungs are surrounded by a visceral pleural membrane
The inner surface of the chest wall is covered by a parietal pleural membrane
The pleural cavity is a fixed volume and contains protein-rich pleural fluid

Question 24

What can interruptions to the pleural cavity cause

Answer 24

haemothorax or pneumothorax

Question 25

Describe the 3 compartment model

Answer 25

Transmural pressures = (Pinside – Poutside)
A negative transrespiratory pressure will lead to inspiration
A positive transmural pressure leads to expiration

Question 26

Describe the procedure for the volume time curve

Answer 26

1. Patient wears a noseclip
2. Patient inhales to TLC
3. Patient wraps lips around mouthpiece
4. Patient exhales as hard and fast as possible
5. Exhalation continues until RV is reached or six seconds have passed

Question 27

What should be assessed on the volume time curve

Answer 27

Slow starts
Early stops
Intramanouever variability

Question 28

How is a volume time graph interpreted

Answer 28

FVC = top of the curve
FEV = volume in 1 second

Question 29

Describe what a volume time graph may look like for a restrictive and obstructive disease

Answer 29

restrictive = slightly reduced FVC, similar FEV, time breath is held for is short
obstructive = reduced FVC and FEV

Question 30

Describe the procedure for peak flow

Answer 30

1. Patient wears noseclip
2. Patient inhales to TLC
3. Patient wraps lips around mouthpiece
4. Patient exhales as hard and fast as possible
5. Exhalation does not have to reach RV
6. Repeat at least twice. Take highest measurement

Question 31

Describe the procedure for the flow-volume loop measurement

Answer 31

1. Patient wears a noseclip
2. Patient wraps lips around mouthpiece
3. Patient completes at least one tidal breath (A&B)
4. Patient inhales steadily to TLC (C)
5. Patient exhales as hard and fast as possible (D)
6. Exhalation continues until RV is reached (E)
7. Patient immediately inhales to TLC (F)
8. Visually inspect performance and volume time curve and repeat if necessary

Question 32

What should be looked out for when assessing the flow-volume loop

Answer 32

Inconsistencies with clinical picture

Interrupted flow data