Sensory aspects of respiratory disease

Question 1

Prevalence of respiratory symptoms?

Answer 1

cough - third most common complaint heard by GP
10-38% patients complain in outpatients
chest pain - most common pain for medical attention sought (35%)
SOB, dyspnoea
haemoptysis

symptoms = physical sensations that lead the patient to seek medical attention

Question 2

Describe the neurophysiology and behavioural aspect of stimuli leading to conscious sensation

Answer 2

Neurophysiological

• sensory stimulus
• sensor/transducer
• excitation of sensory nerve
• integration CNS
• sensory impression

Behavioural aspect response to sensory impression

• sensory impression
• perception
• evoked sensation

Question 3

What are signs of respiratory disease?

Answer 3

= observable features on physical examination

• hyperinflation of chest wall
• dullness on percussion
• increased respiratory rate
• reduced movement of chest

Question 4

What is cough?

Answer 4

defence to protect lower respiratory tract from inhaled foreign material, excess mucus secretion

secondary to mucociliary clearance - important in lung disease when mucociliary function is impaired

Question 5

What is the expulsive phase of cough?

Answer 5

high velocity of airflow

bronchoconstriction and mucous secretion

Question 6

Where are cough receptors?

How do cough receptors work?

Answer 6

= rapidly adapting irritant receptors in airway epithelium

nerves in airways are next to goblet cells
cilia next to goblet cells
nerve in contact with environment so cough is stimulated by receptor when mucous is produced

upper airways, most in posterior wall of trachea, at carina, pharynx, bifurcation in lungs, pleura and pericardial sac
- respond to mechanical and chemical stimuli

Question 7

What are the sensory receptors in the lung and airways?

Answer 7

C fibre
CHEMORECEPTORS
- sensitive to chemicals, irritants and mediators
- free nerve endings
- small unmyelinated fibres
- release substance P, neuropeptide, CGRP

rapidly adapting stretch receptors
INSPIRATION
- small myelinated (A delta)
- mechanical and chemical irritants

slowly adapting stretch receptors
EXPIRATION
- in airway smooth muscle
- myelinated
- mainly in trachea/bronchi
- mechanoreceptors responding to lung inflation