Airway Clearance

Question 1

What is MCC?

Answer 1

Primary clearance mechanism of the airways
Protection mechanism of lungs (lower resp tract)

Question 2

What 2 components does MCC apparatus consist of?

Answer 2

MUCUS
- 2 layers
- mechanical, chemical and biological barrier

CILIA
- move particulate material caught in mucus towards pharnyx

Question 3

What are the 2 layers of mucus and their characteristics?

Answer 3

Sol Layer (periciliary fluid)
- thin, watery aqueous fluid bathing cilia
- minimal resistance to cilial mvt
- low viscosity and elasticity

Gel Layer (mucus layer)
- elastic and viscous
- moved towards the mouth

Question 4

What are the 5 factors increasing MCC?

Answer 4

posture - using gravity
exercise
environment - inhaling particulate matter/irritated airway wall)
drugs
hydration

Question 5

What 3 factors decrease MCC?

Answer 5

increased age
sleep
disease/injury (esp resp)

Question 6

Why do smoking, chronic bronchitis and infection lead to increased mucus volume

Answer 6

Smoking and chronic bronchitis:
Increased size and number of secretory cells

Infection eg pneumonia: inflammatory reaction

Question 7

Explain how dehydrated Sol layer contributes to MCC impairment

Answer 7

Decreased depth of sol layer dehydrates the cilia - they cannot beat effectively
eg in CF due to changes in ion transport

Question 8

How else might asthma and CF impair MCC?

Answer 8

They alter the rheological properties of the mucus - thickness and stickiness. This makes it harder to clear as it adheres to the airway walls.

Question 9

Name the 3 impairments of MCC related to alteration of cilial action

Answer 9

• decreased cilial beat frequency
• destruction of cilia
• immotile cilia (dont move)

Question 10

Explain decreased cilial beat frequency

Answer 10

MCC is slower so mucus builds up
ageing, anaesthetic

Question 11

Name scenarios/conditions where cilia are destroyed

Answer 11

• smoking, chronic bronchitis. bronchiectasis
• infection especially repeated in same area
• mechanical damage eg ETT
• burns
• chemical damage

Question 12

Which disorders cause immotile cilia

Answer 12

Genetic disorders
primary cilial dyskinesia
Kartagener’s syndrome - younger patients

Question 13

Explain the importance of cough and where it can clear secretions from

Answer 13

• main backup mechanism after MCC to clear foreign matter/secretions from airways
• centrally located airways

Question 14

What are the 4 components of an effective cough?

Answer 14

1. deep inspiration to TLC
2. breath hold against closed glottis
3. contraction of expiratory muscles causing big change in intrathoracic pressure
4. glottis opens and rapid expulsion of air

Question 15

How does the large EFR generated by cough clear secretions. Hint 2PLGF

Answer 15

• acceleration of airflow (gas) across secretions (liquid) lining the airway walls = cephalad (mouthward) movement of secretions
• momentum from the gas is transferred to the liquid to detach it from airway walls

Question 16

Explain the two types of flow

Answer 16

Mist Flow
- high EFR
- liquid carried as small droplets in the gas
- coughing
Annular Flow
- lower EFR
- surface of liquid layer moves in waves
- huffing

Question 17

What are the 5 reasons (and example of each) for an ineffective cough which lead to a secretion movement problem?

Answer 17

1. inability to take deep breath in
   - weak inspiratory muscles
   - chest wall/abd pain
2. inability to close glottis
   - neuro
3. weak expiratory muscles
   - SCI deinnervated
4. excessive dynamic compression (closure)
   - floppy airways close with the pressure
5. depressed cough reflex
   - eg sedation

Question 18

what are the 4 components of an effective huff

Answer 18

1. breathe in to specified volume
2. keep glottis and mouth open
3. contract abdominal muscles
4. controlled forced expiration to specified volume

Question 19

describe a mid to low lung volume huff

Answer 19

• medium breath in and exhale longer
• EPP occurs towards peripheral airways

Question 20

describe a high to mid lung volume huff

Answer 20

• big breath in and short sharp exhalation
• EPP occurs closer to central airways

Question 21

what are the 4 stages/aims of airway clearance

Answer 21

1. open up airways to get air behind the mucus
   - ventilate airways distal to mucus
2. loosen/unstick the secretions from the small airways
3. mobilise secretions from more peripheral to central airways
   - EFR increase to move secretions up
   - expiratory flow bias
4. clear secretions from central airways

Question 22

what are the 3 types of breathing exercises for airway clearance

Answer 22

active cycle of breathing techniques (ACBT)
forced expiration technique (FET)
autogenic drainage (AD)

Question 23

what are the 3 components of ACBT

Answer 23

• slow deep breathing (thoracic expansion and inspiratory hold)
• breathing control
• FET (huffs and breathing control)

Question 24

what 2 components make up FET

Answer 24

huffs - 1-2
breathing control
- relaxed breathing
- reduce bronchospasm, desaturation, fatigue

Question 25

what are the 4 ways that airway clearance devices work

Answer 25

• move air behind obstructions
• stabilise floppy airways and keep open
• increase and modulate EFR to move secretions towards central
• change sputum rheology

Question 26

what are the 3 mechanisms behind exercise being used as an adjunct for AC

Answer 26

• may increase ventilation
• may increase EFR to enhance 2PLGF
• may stimulate ANS and increase MCC through cilia beating