Airway Clearance - Pathophysiology Flashcards

1
Q

What is the difference between mucus and sputum?

A

Sputum is mucus from the respiratory tract outside the body (aka phlegm)

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2
Q

What is the normal level of airway mucus?

A

10-100mL mucus produced each day by submucosal glands, goblet cells, clara cells and tissue fluid exudate

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3
Q

What is the function of mucus?

A
  • Mechanical barrier trapping particles
  • Chemical screen (filter/diffusion)
  • Biological barrier (bacterial adhesion/clearance)
  • Airway hydration
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4
Q

What are the characteristics of mucus?

A
  • Normally white/clear (mucoid)
  • Altered colour indicates infection
  • Smell (normally none)
  • Thickness/viscosity
  • Adhesivity
  • Amount
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5
Q

What is the only illness that will produce pink, frothy sputum?

A

Pulmonary oedema

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6
Q

Where are goblet cells located?

A

In the epithelium of the mucosal layer (make up 10% of epithelium in proximal airways, decrease in number in peripheral airways)

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7
Q

What happens to goblet cells in COPD?

A

Increased number, extending peripherally

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8
Q

How can the structure of the alveolar region be described?

A

A pocket of air surrounded by a thin membrane

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9
Q

What channels connect the bronchioles and alveoli?

A

Pores of Kohn: Connect adjacent alveoli
Canals of Lambert: Connect terminal bronchioles
Inter-segmental respiratory bronchioles

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10
Q

What are the 4 mechanisms of airway clearance?

A
  1. Alveolar clearance: Removes insoluble particles
  2. Two phase flow: Airway narrowing on expiration create shear force that moves mucus towards the mouth
  3. Mucociliary clearance (MCC): Clears conducting airways
  4. Cough: Backup system when MCC fails
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11
Q

What 2 mechanisms of airway clearance can we influence?

A

MCC and cough

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12
Q

What cells clear the respiratory tract?

A

Ciliated cells of the periciliary (sol) layer of the mucosa (carry out mucociliary clearance)

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13
Q

Why is the depth of the periciliary (sol) layer important?

A

So the cilia can function correctly and move the mucus along the airways

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14
Q

What do the cilia use to move the mucus/particles?

A

Mucus blanket

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15
Q

What does the speed of MCC depend on?

A

Airway generation (fast movement in central airways)

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16
Q

What happens if the airways are not adequately hydrated?

A

The cilia cannot carry out their function

17
Q

What is the mucus blanket composed of?

A

95% water, 1% salts, 4% lipids, foreign particles, cellular debris

18
Q

In cystic fibrosis, what does the mucus blanket also contain?

A

DNA

19
Q

How does the airway surface fluid (ASF) differ between healthy people and CF/infected patients?

A

Healthy: ASF is hypotonic

CF/infected: ASF is isotonic (dehydrated airway mucus secretions)

20
Q

What are the factors that affect MCC?

**Exam Q!

A
  • Age (slows in elderly)
  • Sleep (decreases)
  • Hairspray (decreases)
  • Posture (gravity increases MCC if MCC impaired)
  • Exercise (increases)
  • Pollutants
  • Smoking (variable)
  • Medications
  • Disease
21
Q

In chronic bronchitis, what percentage does cough increase sputum clearance by?

A

20% (compared to 2.5% increase in healthy people)

22
Q

What are the 4 steps of a quality cough?

**Need to know

A
  • Inspiration of volume of air
  • Glottis closed (opening btwn vocal cords)
  • Simultaneous contraction of expiratory muscles resulting in large increase in intrathoracic pressure
  • Glottis is open, rapid expiratory flow of air
23
Q

Why is a deep breath important for an effective cough?

A
  • More areas of lung receive ventilation
  • Greater elastic recoil pressure of lungs
  • Muscles at better position (length/tension relationship)
  • Changes equal pressure point within airways
24
Q

Where is the equal pressure point (EPP)?

A
  • Located around the level of the trachea at high lung volumes
  • Moves peripherally as lung volume decreases
25
Q

What is the EPP?

A

The point where the pressure inside the airways is equal to the pressure surrounding the airways

26
Q

Where does dynamic compression occur?

A

Downstream from the EPP (towards the mouth) and acts to shear the mucus from the airway walls

27
Q

What happens to the EPP in a normal cough?

A
  • Expiratory muscle activity causes dynamic compression of trachea & intrathoracic airways
  • Dynamic compression increases velocity of air downstream from EPP, applying a shearing force
  • Airflow causes misting of mucus
  • Enhanced movement of mucus from trachea, inner/intermediate regions of lungs (not outer)
28
Q

What are the adverse effects of vigorous coughing?

A
  • CV (decrease BP, cardiac rhythm disturbances)
  • Genitourinary (incontinence)
  • GI (reflux, inguinal hernia)
  • Musculoskeletal (rib fracture)
  • Neuro (syncope, headache)
  • Respiratory (airflow limitation, pneumothorax)
29
Q

Why can coughing be exhausting?

A

It produces high intrathoracic pressures and is associated with high energy consumption

30
Q

What is a huff?

A

Maintains open glottis, prolonged less explosive expulsion of air

31
Q

What are the benefits of a huff?

A
  • Similar effect on mucus clearance
  • Energy efficient, less painful
  • Manipulates EPP to pick up sputum more distally into the airway
32
Q

What are the 3 main causes of impaired airway clearance?

A
  1. Excessive sputum production
  2. Impaired MCC
    - E.g. medications, general anaesthetic, bronchiectasis, CF
  3. Failure of cough
    - Pain following surgery
    - Chest wall trauma
    - Denervated lungs post lung transplant
    - Neuromuscular conditions e.g. Guillain Barre syndrome
    - Drowsiness/confusion
33
Q

What is the significance of retained airway secretions?

A
  • Increased airway resistance (harder for lungs to expand)
  • Can obstruct an airway causing distal collapse
  • Site for bacterial infection
  • Can cause airway destruction & cycle of impaired clearance (e.g. CF, bronchiectasis)
34
Q

What is important to remember about sputum clearance problems?

A

Lots of sputum doesn’t always = problem
Someone can have lots of sputum, but if they can clear it effectively they don’t have a sputum clearance problem
OR
Someone can only have a little sputum, but if they can’t clear it effectively they do have a sputum clearance problem

35
Q

What are the 2 phases of a pneumonia illness?

A

Consolidation (solid in lungs)

Resolution (sputum)

36
Q

What is important to remember about the consolidation phase?

A

Sputum is still in a solid state, so clearance techniques will not work. Need to wait a few days until it is broken down before beginning sputum clearance

37
Q

What is bronchiectasis?

A

When part of the airway becomes widened and floppy (ballooned-out pocket that fills with sputum)