Cough: Mechanisms, Causes + Pharmacological Therapy Flashcards
What is a chronic cough?
> 8 weeks
What does the cough reflex involve?
Central + peripheral mechanisms
What is the central mechanism for a cough reflex?
Cough centre in medulla oblongata receives stimuli
Initiates reflex response
What is the peripheral mechanism for a cough reflex?
Cough receptors in pharynx, larynx, trachea or lungs
Stimulated by air, dryness of mucous or excessive secretions
Describe what happens when you cough
Cough receptor stimulated
Vagus + glossopharyngeal nerves transmit impulse to cough centre
Impulse transmitted to larynx + intercostal + abdominal muscles
Deep inspiration followed by closure of glottis, relaxation of diaphragm + contraction of muscles
Increased pressure = open glottis releases forceful expiration, cough
What are the 3 types of cough receptors?
Rapidly adapting receptors (RARs)
Slowly adapting receptors (SARs)
Nociceptors on C-fibres
Describe RARs
Respond to mechanical stimuli = smoke, ammonia, acidic/alkaline solutions
Describe nociceptors on C-fibres
Respond to chemical stimuli = histamine, prostaglandins
What is an example of exogenous source?
Smoke, dust, fumes, foreign bodies
What is an example of endogenous origin?
Upper air secretions, gastric contents
What is most common cause of chronic cough for a non-smoker?
Postnasal drip
When should a cough be evaluated?
Chest pain
Fever
Weight loss
Blood-tinged sputum
When is a cough productive?
Secretions are expectorated
When is a cough non-productive?
Dry, no sputum
What conditions are associated with dry cough?
Laryngitis
Smoking cough
Pneumonia
TB
Lung cancer
What conditions are associated with wet cough?
Acute viral diseases
Bronchitis
Pneumonia
TB
Bronchiectatic disease
What is a fat cough?
Formation of phlegm in the bronchi
What is sputum?
Released during coughing process
What is phlegm?
Formed in the body
Why is phlegm produced?
Body wants to clear the body of foreign bodies
What is an acute cough?
<3 weeks
What is a sub-acute cough?
Between 3 - 8 weeks
What are the different treatments for cough?
Antitussives
Expectorants
Mucolytics
Antihistamines
Bronchodilators
Pharyngeal demulcents
What do antitussives do?
Supress cough by depressing cough centre
What are examples of centrally acting antitussives?
Narcotics = codeine
Non-narcotics = dextromethorphan
What are examples of peripherally acting antitussives?
Lidocaine antihistamines
SYRUPS
Act on cough receptors
What are examples of locally acting antitussives?
Throat lozenges, cough drops
How do locally acting antitussives work?
Supress cough by increasing flow of saliva
Include demulcents to decrease irritation of pharyngeal mucosa
What are examples of oral cough suppressants?
Codeine + hydrocodone
Dextromethorphan
Diphenhydramine
What does codeine + hydrocodone require?
Doctor’s prescription
Describe dextromethorphan
Oral cough suppressant
OTC
Chemically related to codeine BUT not pain-relieving
Describe diphenhydramine
1st generation antihistamine = “drowsy”
Recommended for night time
How do expectorants work?
Increase leaking of fluid into airways
Thins the thick mucus + facilitate the clearing
Describe guaifenesin
Most common expectorant
Describe mucolytics
Break bonds between mucus
May be nebulised into face mask or mouthpiece
What are some examples of mucolytics?
Sodium chloride + acetylcysteine
What are examples of topical medications?
Camphor + methanol
What do you do with topical medications?
Rubbed on to throat + chest as a thick layer
