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Flashcards in 17. Breathlessness Deck (17):
1

Define dyspnoea

Difficult or laboured breathing in which the subject is conscious of being short of breath aka. breathlessness

Definition of breathlessness: undue awareness of breathing or awareness of difficulty breathing

2

What is meant by breathlessness?

Sensations of all or any of the below:
Awareness of breathing normally absent
A sensation of air hunger/requiring more air
Difficulty breathing in
Difficulty breathing out
Feeling that the chest is filled up
Perception of respiratory rate and gasps or sighs

3

What is the pathophysiology of breathlessness ? (Brief)

Three main components - afferent input, efferent output, central information processing

Central processing in dyspnoea results in mismatch between the afferent and the efferent - so the need for ventilation is not met by the physical breathing

4

What are the causes of breathlessness?

Hypoxia
Metabolic acidosis
Hypotension/reduced cardiac output
Breathing CO2
Exercise
Pregnancy
Anxiety
Pulmonary oedema
Anaemia
Obstruction of the pulmonary artery

5

By what mechanism does hypoxia, metabolic acidosis and hypotension cause dyspnoea/breathlessness?

By a low pO2/altered pH being recognised by the peripheral chemoreceptors

6

How does the function of the respiratory muscles change when there is airway obstruction?

When there is resistance i.e. airway obstruction, brain activity increases with increased input from the chest wall muscles and their stretch receptors

7

What are J receptors and how do they function in the lung?

AKA. Pulmonary C-fibre receptors
J receptors are situated next to capillaries in the bronchial wall
These are slow speed C fibres and result in vagal input to the brainstem
Activation of these receptors leads to shortened expiration and increased respiratory frequency

8

What can activate J receptors?

Local congestion i.e. pneumonia, pulmonary emboli, pulmonary odoema, congestive heart failure - essentially any cause leading to a reduced oxygenation of the lung

9

What does the activation of J receptors result in?

Activation causes a reflexive increase in breathing rate and so leads to increased rate of ventilation

10

What neurological factors can lead to breathlessness?

Anxiety
Depression
Temperature
Hormones
Hyperventilation
Desensitisation and acclimatisation

11

What different tests can be used to test lung function?

Tests of airflow and resistance
Tests of lung volume with measurement of residual volume and air trapping
Tests of gas transfer
Repeated measurements over time
Exercise testing

12

Why are transplant patients particularly prone to becoming breathless?

These patients have no input via the J receptors or stretch receptors and so have no mechanism to prevent the sensation of breathlessness

13

What treatments can be used for breathlessness?

Find the cause and treat it
(Bronchodilators and steroids
Oxygen
Morphine
Diazepam
Retraining and exercise)

14

How can exercise cause breathlessness?

Increases the pCO2 level
Sensed via afferents from the skeletal muscles
Stimulates the respiratory centre

15

How does pregnancy lead to breathlessness?

Due to direct effect on the respiratory centre due to increased levels of progesterone
Also results in an increased CO2 production

16

How does pulmonary oedema cause breathlessness?

Stimulation of the J receptors of the lungs

17

How can patients present with breathlessness?

Shortness of breath
Cough
Sputum
Wheeze
Chest pain
Palpitations
Systemic symptoms e.g. night sweats and weight loss