Cough Flashcards
what is cough?
Cough is a reflex response to airway irritation.
Protective reflex that removes foreign material and secretions from the bronchi and bronchioles
what are the 2 types of cough?
Dry cough: usually felt in the throat as a tickle that sets off the coughing
Productive: chesty cough usually produces phlegm.
what is acute cough?
Duration: less than 3 weeks
Causes:
Most common: upper respiratory tract infections
Acute bronchitis, pneumonia, acute exacerbations of asthma, COPD, and bronchiectasis, foreign body aspiration.
what is sub-acute cough?
Duration: 3–8 weeks.
Causes: After an obvious respiratory infection Persistent pneumonia Acute bronchitis Pertussis (whooping cough) Other types of post-infectious cough (infection has resolved but the cough persists)
No an obvious respiratory infection
Early development of a chronic cough.
(Persistent infections
Unknown mechanisms
Developing chronic cough)
what is chronic cough?
Duration: more than 8 weeks
Causes: Smoking or disease-related COPD Asthma Cancer TB Gastro-oesophageal reflux Upper airway cough syndrome most commonly caused by chronic rhinitis or chronic sinusitis.
Medicine-related
Angiotensin-Converting Enzyme inhibitors.
(Smoking-related causes Drugs
Airways inflammation
Gastro-oesophageal reflux)
explain the airway sensory nerves and which initates the cough
Airway sensory nerves are mainly carried via the vagus nerve, where they terminate both in and under the airway epithelium.
Cell bodies for airway nerve fibres originate in two ganglia, the jugular and nodose, which are located under the ear bone within the head.
These fibres consist of the C-fibres, Aδ-nociceptors, polymodal Aδ-fibres (‘cough receptors), rapidly adapting receptors (RARs), and slowly adapting receptors (SARs), which sense both chemical and mechanical stimuli.
Of these fibres, the chemosensitive C-fibres and mechanosensitive polymodal Aδ-fibres are thought to mediate cough.
Once these fibres are stimulated stimulated, information is carried along the vagus nerve via the nodose and jugular sensory ganglia to the solitary tract nucleus (NTS), located in the medulla.
In the NTS the sensory fibres synapse to second-order neurons which relay the message to a respiratory pattern generator, activating efferent motor neurons, and leading to cough. The C-fibres also contain neuropeptides, which are released upon nerve activation in some species and lead to neurogenic inflammation
give a step by step of cough reflex?
1) Once mechano- and chemo- receptors / fibres are stimulated,
2) information is carried along the vagus nerve via the nodose and jugular sensory ganglia to the solitary tract nucleus (NTS), located in the medulla.
3) In the NTS the sensory fibres synapse to second-order neurons which relay the message to a respiratory pattern generator,
4) activating efferent motor neurons
5) leading to cough.
The C-fibres also contain neuropeptides, which are released upon nerve activation in some species and lead to neurogenic inflammation
what is the management of cough (non-pharmacological)
Acute viral cough almost invariably benign and self limiting
Prescribed treatments can be regarded as unnecessary
However, it can be distressing and cause significant morbidity.
Benefit from various over-the-counter preparations
Home remedy
Simplest and cheapest e.g., honey and lemon.
what is treatment options for cough for children?
and possible side effects
Children under the age of 6 should not be given over –the- counter cough and cold treatments containing cough medicines (BNF cough and congestion chapter)
Side effects
Allergies
Sleep problem
Hallucinations
Warm drink of lemon and honey
Cough syrup containing glycerol and honey
what is the pharmacological cough treatments?
Antitussives. Inhibit the cough reflex by:
Reducing sensory reception activation
Depressing cough centre in brainstem
Sedative antihistamines
Mucolytics
Expectorants
what is the pharmacological cough treatments?
Antitussives. Inhibit the cough reflex by:
Reducing sensory reception activation
Depressing cough centre in brainstem
Sedative antihistamines
Mucolytics
Expectorants
what is the role of antitussives?
To Reduce Sensory Reception Activation
To Reduce Sensitivity of Cough Centre
what are examples of antitussives and what is their use?
To Reduce Sensory Reception Activation
Menthol vapour
Topical anaesthetic
Peripherally acting: reduce sensitivity of peripheral sensory cough receptors in pharynx and larynx to irritation
USE: treatment of productive and non-productive cough
what is the role of menthol and what class of drug does it go under?
By inhalation suppresses the cough
Menthol crystals or proprietary capsules
Cough suppression is acute and short lasting
Placebo effect?
- antitussive
what are examples of drugs which To Reduce Sensitivity of Cough Centre (antitussives) and what is their use?
Dextromethorphan
Codeine
Pholcodine
Centrally acting: agonists of opioid and non-opioid receptors, depress the cough centre in brainstem
USE: For treatment of dry cough ONLY
Administration: oral
Do not combine with mucolytics or expectorants
what is dextromethorphan
Non-sedating opiate (synthetic opioid, codeine analogue)
Antitussive mechanism still unclear
OTC drug. Available as liquid and lozenges
Some preparations suitable for children under 12 years old
Dextro:
shows high affinity binding to several regions of the brain, including the medullary cough center
is an opioid-like drug that binds to and acts as antagonist to the NMDA glutamatergic receptor,
it is an agonist to the non-opioid sigma 1 and sigma 2 receptors,
it is also an alpha3/beta4 nicotinic receptor antagonist
targets the serotonin reuptake pump
what is codeine and side effects
who should not use it ?
An opioid analgesic that suppress cough through a direct effect on the cough centre in the medulla
Related to morphine, less potent analgesic properties and mild sedative effects
Class B controlled drug
Concentrations <15 mg in OTC
(Codeine Phosphate Linctus)
High-dose is prescription only
Unwanted effects: Dependence! Not suitable for long-term use Inhibiton of ciliarly clearance Constipation Drowsiness
Not greater efficacy than dextromethorphan but greater adverse side effects!
Do not use in:
Patients with asthma (respiratory depression)
In patient under 18 years
what is pholcodine
Opioid receptor agonist
Class B controlled drug
As effective as codeine but with attenuated side effects
In the UK, pholcodine is a component of many over the counter cough medications, for the relief of acute non-productive cough associated with upper respiratory tract infections. In the US, pholcodine is classed as a Schedule I drug and is not prescribed.
- daynurse
- benylin dry cough
what are examples of sedative antihistamines and their use?
Diphenhydramine
Chlorphenamine
First generation H1 antihistamines with sedative properties
USE: Suppress cough but also cause drowsiness treatment for nocturnal cough
Interaction with other drugs e.g., antidepressant, drugs that cause drowsiness
Note: trials have concluded that antihistamines are not more effective than placebo in relieving cough!
what are examples of mucolytics and their effects
Carbocisteine
Mecysteine
N-acetylcysteine
Effects: cleave disulphide bonds cross-linking mucus glycoprotein to reduce viscosity of bronchial secretion (liquefy mucus/phlegm)
what is the mechanism of action of acetylcysteine?
The mechanisms of action for acetylcysteine’s well-known mucolytic effects are different. In particular, when inhaled, acetylcysteine (and its metabolic by-product cysteine) exerts its mucolytic action through its free sulfhydryl group, which reduces the disulfide bonds in the mucus matrix and lowers mucus viscosity. This action increases with increasing pH and is most significant at pH 7 to 9
what are examples of expectorant and their effect?
White Squill Ipecacuanha Guaifenesin Creosotes Volatile oils
Effects:
Reduce adhesiveness and surface tension of mucus
Promote expulsion of mucus by encouraging productive cough and bronchial secretion
NOTE: Very little clinical evidence to support their value in treating cough!!
help bring phlegm up making coughing easier
what is covid 19 guidelines and advices
Encourage patients with cough to avoid lying on their back because this makes coughing ineffective.
Management:
Simple measures first: honey
Consider treatment with codeine linctus, codeine phosphate tablets (first choice) or morphine sulfate oral solution (second choice) to suppress coughing if it is distressing
Consideration
Risks of constipation - consider regular stimulant laxative
Avoid cough suppressants in chronic bronchitis and bronchiectasis (sputum retention )
