86 - Physiology of Breathlessness

Question 1

What can cause a weak, hoarse voice?

Answer 1

Impingement upon recurrent laryngeal nerve.

Question 2

Effect of impinged recurrent laryngeal nerve on coughing

Answer 2

Paralyses larynx. Impaired cough.

Question 3

Definition of breathlessness

Answer 3

Recognition be the subject of an inappropriate relationship between respiratory work and total body work.

Question 4

Things contributing to work of breathing
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2

Answer 4

1) Stretching work (elastic)

2) Airflow work (resistive)

Question 5

Resistive work of breathing

Answer 5

Resisting friction of air going through airways (normally very low, as flow of air is normally laminar).

Question 6

Things that increase sensation of SOB

Answer 6

Increased load (increased work of breathing)
Increased drive (EG: anxiety, hypoxia, anaemia, metabolic acidosis)

Question 7

Broad categories of disorders that can lead to dyspnoea
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2
3
4
5
6

Answer 7

Respiratory
Cardiac
Muscle weakness
Metabolic
Anaemia
Psychogenic

Question 8

Respiratory causes of dyspnoea
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2
3
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5

Answer 8

1) AIRWAYS DISEASE
a) Upper airways - tumour, foreign body, angioneurotic odema, CROUP
b) Lower airways - asthma, COPD, bronchiolitis
2) ALVEOLAR DISEASE
Pneumonia, lung collapse, pulmonary odema, pulmonary fibrosis
3) PULMONARY VASCULAR DISEASE
Pulmonary embolism, vasculitis, primary pulmonary hypertension
4) PLEURAL and CHEST WALL DISEASE
Pleural effusion, pneumothorax, chest wall deformity
5) RESPIRATORY MUSCLE DISEASE
Respiratory muscle weakness, phrenic nerve palsy

Question 9

Things that can cause SOB, cough, sputum, wheeze or stridor

Answer 9

Airways problem.
Sputum comes up from airways.
Wheeze (lower airway obstruction), stridor (upper airway obstruction) from airways.

Question 10

When are CT scans used for airway problems

Answer 10

Bronchiectasis, cancer

Question 11

Appearance of lower airway obstruction on a flow/volume loop

Answer 11

Lower peak flow, sharp drop off after this

Question 12

What does reduced diffusing capacity tell you?

Answer 12

Impairment of blood/alveolar membrane

Question 13

SOB, cough, crepitations diagnosis

Answer 13

Crepitations from alveolar membrane dysfunction. Can be from air bubbling through fluid (oedema), sudden opening of airways during inspiration (stiff lungs, interstitial lung disease).

Indicates that problem is in terminal bronchioles, alveoli.

Question 14

SOB+/- haemophtysis, pain

Answer 14

Could be pulmonary embolism, pulmonary hypertension, pulmonary vasculitis (rare).

Pain could be from pleural inflammation.

Use risk factors (contraceptive pill, smoking, immobility, etc) to refine diagnosis.

Question 15

MUD

Answer 15

Medically undiagnosed dyspnoea

Question 16

How often can dyspnoea be diagnosed?

Answer 16

~80% of the time.

Question 17

Proportion of atopic asthma in the general adult population

Answer 17

~12-15%

Question 18

How can athletic breathlessness be diagnosed?

Answer 18

Eucapnoeic voluntary hyperventilation

Question 19

Condition that can be confused with asthma
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3
4

Answer 19

Vocal cord dysfunction.
Negative eucapnoeic voluntary hyperventilation.
Abnormal endoscopy.
Responds to speech therapy.

Question 20

How can you decide if breathlessness is from being deconditioned, or something else?

Answer 20

Incremental exercise test.

Three month aerobic training program and then re-measure exercise capacity. Should improve if just deconditioned.

Question 21

Appearance of incremental exercise test with someone who is deconditioned
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2
3
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5

Answer 21

Low work load and VO2max
• Steep heart rate response (small stroke volume)
• Early anaerobic threshold
• Excessive VEmax
• No ECG, BP abnormalities or low SaO2

Question 22

How can you determine if SOB is psychogenic?

Answer 22

Increase suspicion of MUD:
Need to take deep inspiration
Oppressive chest
Anxiety
Tingling in fingers, face, head.

Absence of following symptoms
Wheezing, cough, stridor