11. Sensory aspects of respiratory disease Flashcards
Symptom
An abnormal sensation that leads someone to seek medical attention
e.g. Cough, Chest pain
Sign
An observable feature on physical examination e.g. Increased respiratory rate
Describe the pathway from stimulus to evoked sensation? What are the names for the 2 main parts of this?
Stimulus - transducer - excitation of sensory nerves - integration of CNS - sensory impression
= NEUROPHYSIOLOGY
Sensory impression - perception - evoked sensation
=BEHAVIOURAL PSYCHOLOGY
Cough
A crucial defence mechanism protecting the lower respiratory tract from:
inhaled foreign material
excessive mucous secretion
Expulsive phase of cough
generates a high velocity of airflow
facilitated by bronchoconstriction and mucous secretion
Describe the distribution of rapidly adapting irritant receptors within the airway epithelium.
Most on posterior wall of the trachea and in the main carina.
Decrease in number as you go down the airways and are absent in the bronchioles.
Commonly found at the branch points of large airways.
What is the most important nerve involved in cough?
Vagus nerve
Stimuli of cough receptors
Laryngeal and tracheobronchial receptors respond to chemical and mechanical stimuli
What are the 3 main types of sensory receptors in the lungs and airways?
C-fibre receptor
Slowly adapting stretch receptors
Rapidly adapting stretch receptors
Which nerve do all the sensory receptors in the lungs and airways pass through?
Vagus nerve
What is used as a stimulus for the C-fibres?
Caspaicin
What stimulates C-fibres?
Chemicals
Describe C-fibres structure, distribution and action
“Free” nerve endings
Larynx, trachea, bronchi, lungs
Small unmyelinated fibres
Release neuropeptide inflammatory mediators e.g. Neurokinin A
Describe rapidly adapting stretch receptors (RARs) structure and distribution
Naso-pharynx, larynx, trachea, bronchi
Small, myelinated nerve fibres (A-delta)
What stimulates RARs?
Mechanical, chemical irritant stimuli, inflammatory mediators
What do the rapidly and slowly adapting stretch receptors respond to?
Inflation (increase in tracheal pressure)
Describe the differences between the 3 types of sensory receptor.
C-fibres are unmyelinated whereas the others are myelinated.
C-fibres are found in the larynx, trachea, bronchi and lungs
Rapidly adapting stretch receptors are found in the naso-pharynx, larynx, trachea and bronchi
Slowly adapting stretch receptors are located on airway smooth muscle, mainly in the trachea and main bronchi
What are the 2 broad types of sensory receptor in the airways?
Mechanoreceptors
Nociceptors
What do Mechanoreceptors respond to?
Mechanical stimulus
Citric acid
What are Nociceptors activated by?
Chemicals
What is the collection of neurons in the cough centre called?
Nucleus tractus solitarius
What is the Nucleus tractus solitarius connected to?
Medullary cough pattern generator
What is the role of the cerebral cortex in the complete cough pathway?
Generate a cough and generate the urge to cough.
When asleep/ anaesthetised, this component of the complete cough pathway is inhibited so a certain degree of wakefulness is needed to cough.
How do signals reach the brain to inform us to cough?
Superior laryngeal nerve and vagus nerve lead to “cough centre”
What is needed to be coordinated by the efferent neural pathway for cough?
Glottic muscles
Inspiratory and expiratory muscles
What are the 3 phases of cough?
Inspiratory phase Glottic closure (Pressure increases) Expiratory phase (Opening of glottis, produces high flow)
What is acute cough and what is it usually caused by?
Cough that lasts < 3 weeks
Common cold
What are the 5 common causes of chronic cough?
Asthma Gastrooesophageal reflux Rhinosinusitis Chronic bronchitis Bronchiectasis
What is chronic cough?
Persistent cough that lasts > 3 weeks
What is another name for chronic cough? How can the sensitivity be tested?
Cough hypersensitivity syndrome
Give patients increasing concs. of caspaicin until they cough.
People with cough hypersensitivity syndrome will have relatively low tolerance of caspaicin.
Name 5 triggers in cough hypersensitivity syndrome
Deep breath Laughing Talking too much Vigorous exercise Smells (perfumes, vinegar)
List 3 causes of cough hypersensitivity syndrome
Excitability of afferent nerves increased by chemical mediators e.g. prostaglandin E2
Increase in receptor numbers e.g. TRPV-1 (capsaicin receptor)
Neurotransmitter increase e.g. neurokinins in brain stem
Name 2 symptomatic suppressant therapies for cough
Central action:
Opiates based e.g. Codeine
Peripheral action:
Moguistine, Levodopropizine
Name the disease-specific therapies for Eosinophil-associated and Gastro-oesophageal reflux disease coughs
Eosinophil-associated: Inhaled corticosteroids
GERD: Proton pump inhibitors, Histamine H2 antagonists
Management of cough hypersensitivity syndrome as sensory neuropathic cough:
Speech pathology management
Increase voluntary control
Decrease cough sensitivity
Decrease laryngeal irritation
Decrease laryngeal muscle contraction
Management of cough hypersensitivity syndrome as sensory neuropathic cough:
Pharmacology
Amitryptiline
Gabapentin
Opiates: morphine, codeine, dextrometorphan
Experimental: TRPV1 blockers, TRPA1 blockers
Sensory perception from the nose and the pharynx goes through which nerves?
Nose: Trigeminal (V)
Pharynx: Glossopharyngeal (IX) and vagus (X)
Sensory perception from the larynx, lungs and chest wall goes through which nerves?
Larynx: Vagus (X)
Lungs: Vagus (X)
Chest wall: Spinal nerves
Describe the anatomical pathways of touch and pain.
Touch and pain differ in the level at which they cross over to the other side of the spinal cord.
Touch crosses over at the level of the caudal medulla (Somatosensory cortex)
Pain crosses over immediately
(Spinothalamic tract)
Name 4 ways in which visceral pain differs from somatic pain
Visceral pain is difficult to localise
Visceral pain is diffuse in character
Visceral pain is referred to somatic structures
There are fewer visceral afferents than somatic afferents
Chest pain from respiratory symptoms
Pleuropulmonary disorders: Pleural inflammation e.g. infection, PE
Tracheobronchitis: Infections, inhalation of irritants
Inflammation or trauma to chest wall: Rib fracture, Muscle injury
Chest pain from non-respiratory disorders
Cardiovascular disorders: e.g. Myocardial ischaemia/infarction
Gastrointestinal disorders: e.g. Oesophageal rupture
‘Psychiatric disorders’ : e.g. Panic disorder
Dyspnoea
Troublesome shortness of breath reported by a patient
What scale is used to grade dyspnoea?
Modified Borg Scale
What are the 3 types of dyspnoea?
Air Hunger
Tightness
Work/Effort of breathing
How is dyspnoea treated?
Treatment of dyspnoea itself is difficult
Treat the cause e.g. if respiratory or cardiovascular
List 4 common therapeutic options to treat dyspnoea
Add bronchodilator
Drugs affecting brain e.g. morphine, diazepam
Lung resection (e.g. lung volume reduction surgery)
Pulmonary rehabilitation (improve general fitness, health and psychological well-being)
