Pathophysiology of Cough

Question 1

What is cough?

Answer 1

a protective mechanism that ensure the removal of mucus, noxious substances and infectious organisms from the larynx, trachea and large bronchi.

Question 2

how many weeks does it take before cough is considered ‘chronic’?

Answer 2

> 8 weeks

Question 3

what is the mechanism of cough in the central nervous system?

Answer 3

1. cough receptors stimulated
2. vagus and glossopharyngeal nerves send impulses to cough centre in medulla
3. impulse transmitted to the larynx, intercostal muscles and abdominal muscles.
4. deep inhalation followed by closure of glottis
5. diaphragm relaxes and abdominal and intercostal muscles contract
6. lung pressure increases
7. glottis forced open
8. noisy expiration known as cough

Question 4

Where is the cough centre located?

Answer 4

in the medulla

Question 5

Where are cough receptors located?

Answer 5

• nose
• sinuses
• auditory canals
• nasopharynx
• larynx
• trachea
• bronchi
• pleurae
• diaphragm
• pericardium
• GI tract

Question 6

what is the peripheral mechanism of cough?

Answer 6

cough receptors in the pharynx, larynx, trachea, or lungs may be stimulated by air, dryness of mucous membranes, or excessive secretions.

Question 7

what are the three predominant types of receptors?

Answer 7

1. Rapidly adapting receptors (RARs)
2. Slowly adapting receptors (SARs)
3. Nociceptors on c-fibres.

Question 8

what are Rapidly adapting receptors (RARs)?

Answer 8

receptors that respond to mechanical stimuli, cigarette smoke, ammonia, acidic and alkaline solutions, hypotonic and hypertonic saline, pulmonary congestion atelectasis and bronchoconstriction

Question 9

what are Nociceptors on c-fibres?

Answer 9

receptors that respond to chemical stimuli as well as inflammatory and immunological mediators e.g. histamine, bradykinin, prostaglandins, substance P, capsaicin, acidic pH

Question 10

what is the difference between productive and non-productive cough?

Answer 10

productive - secretions

non-productive - dry and no sputum

Question 11

what are common causes of chronic cough in non-smokers?

Answer 11

• postnasal drip
• asthma
• GORD

Question 12

what is ‘fat cough’?

Answer 12

when phlegm is formed around the bronchi causing one to cough

Question 13

what is acute cough?

Answer 13

cough that has lasted less than 3 weeks and is due to upper respiratory infections e.g. a cold, pneumonia

Question 14

what is sub acute cough?

Answer 14

cough lasting between 3-8 weeks and is commonly post-infectious resulting from consistent airway inflammation.

Question 15

What is chronic cough?

Answer 15

cough lasting for more than 8 weeks due to infections/diseases e.g. asthma, COPD, smoking etc

Question 16

what is asthma?

Answer 16

a chronic inflammatory disease of the airways characterised by increased responsiveness of the tracheobronchial tree to stimuli. Bronchi is narrowed resulting in wheezing, cough and dyspnea.

Question 17

What are the two main mechanisms of cough in GORD?

Answer 17

1. Macro/Micro aspiration of oesophageal contents into tracheo-bronchial tree
2. Acid in distal oesophagus stimulate a mediated oesophageal-tracheobronchial cough reflex.

Question 18

6 ways to treat cough?

Answer 18

1. Antitussives
2. Expectorants (mucokinetics)
3. Mucolytics
4. Antihistamines
5. Bronchodilators
6. Pharyngeal demulcents

Question 19

How do antitussives work?

Answer 19

By suppressing the cough centre in the medulla oblongata or the cough receptors in the throat, trachea or lungs.

Question 20

Three types of antitussive are…?

Answer 20

1. Centrally acting
2. Peripherally acting
3. Locally acting

Question 21

How do locally acting antitussives work?

Answer 21

By either increasing flow of saliva to the site, or by containing demulcents or local anaesthetics to decrease irritation of pharyngeal mucosa.

Question 22

4 examples of oral cough suppressants are…?

Answer 22

1. Codeine
2. Hydrocodone
3. Dextromethorphan
4. Diphenhydramine

Question 23

What are expectorants?

Answer 23

Agents given orally to remove the fluid out of lung tissue into the airways. This liquefies the mucous in the airways allowing for their easier removal when one coughs.

Question 24

What is the most commonly used expectorant?

Answer 24

Guaifenesin

Question 25

What are the only 2 agents recommended for use as mucolytics?

Answer 25

Sodium chloride and acetylcysteine

Question 26

What do mucolytics do?

Answer 26

Liquefy mucous in the respiratory tract

Question 27

What are two examples of topical treatments and where are they administered?

Answer 27

Camphor and menthol ointments and are rubbed on the chest and throat to relieve cough