Sensory aspects of respiratory disease Flashcards
What is the difference between symptoms and signs?
Symptoms: abnormal or worrying sensation that leads person to seek medical attention e.g. Cough/chest pain/SOB
Signs: observable features on physical examination e.g. Hyperinflation, dullness on percussion, increased resp rate
Describe the prevalence of respiratory symptoms:
Cough: 3rd most common GP complaint
Chest pain: most common pain for patients seeking medical help
SOB/dyspnoea: up to 1/4 general population will report
What are respiratory sensory receptors?
Rapidly adapting irritant receptors are present in upper airways, larynx, trachea and large airways but less so in more distal airways, responding to chemical and mechanical stimuli
What are C-fibre receptors?
Have free nerve endings in the larynx, trachea, bronchi and larger bronchioles that are unmyelinated and are stimulated by chemicals (release neuropeptide inflammatory mediators in response to stimuli)
What are Rapidly adapting stretch receptors?
Activated by stretch on inspiration and are small, myelinated fibres in the large airways that respond to mechanical, chemical and inflammatory stimuli
What are the pulmonary Afferent neural pathways
Stimulation of irritant receptors leads to firing down Vagus nerve to cough centre in medulla
What are the pulmonary Efferent neural pathways
Activate motor pathways to effect changes in breathing and cause expiratory airflow
What happens to produce a cough?
Irritant receptors stimulated, afferent pathway via Vagus nerve to cough centre in medulla, motor pathway causes stimulation of glottic and expiratory muscles
Describe the physical events in a cough:
Inspiratory phase with negative flow during inhalation
Glottic pressure in the minimum flow phase (glottis closes to generate pressure)
Glottis opening
Expiratory phase
Describe the trachea during a cough:
Intrathoracic pressure increases causing invagination of the trachea to form a crest shape and increase flow
What are the common causes of a cough?
Acute/chronic infection, airway disease, parenchymal disease, tumours, aspirated foreign bodies, middle ear pathology, CVD and drugs
What are the possible causes of an acute cough?
(<3 weeks): caused by common cold, linked to post nasal drip, throat clearing, nasal blockage and nasal discharge
What are the possible causes of a chronic cough?
(>3 weeks): may be asthma, GO reflux, postnasal drip, chronic bronchitis, bronchiectasis, ACE inhibitors, post-viral and 10% idiopathic
What is the function of a cough?
Defence mechanism to protect LRtract from inhaled foreign material and excess mucous secretion, secondary to mucociliary clearance.
What are the two types of treatment for a cough?
Symptomatic suppressants
Disease-specific
What are symptomatic suppressants for a cough?
Opiates (codeine/dextromorphan) act centrally, while moguistine/levodropropizine act peripherally
What are Disease-specific treatments for a cough?
Corticosteroids if eosinophil problem, steroids for post-nasal drip and proton pump inhibitors for GORD (gastro-oesophageal reflux disease)
What are the two types of chest pain that are experienced?
Somatic pain
Visceral pain
What is somatic chest pain?
Well localised and specific due to the highly specific innervation of muscles and dermatomes
What is visceral chest pain?
Not the same as somatic pain and is difficult to localise and diffuse in character because the number of visceral afferents is less than the number of somatic afferents - thoracic visceral pain often presents similarly with overlapping patterns of referral, localisation and quality
Describe the afferent neural pathways of chest pain:
Pain uses the spino-thalamic tract, with a-delta/C-fibres entering the dorsal horn, immediately crossing and then passing up the tract to the thalamus and then to the primary somatosensory cortex
What are the brain regions involved in sensing chest pain?
Somatosensory processing occurs in the primary somatosensory cortex (motor in the cerebellum, attentional in primary somatosensory and autonomic in the cingulate/insular cortexes)
What is referred pain?
Pain that appears to arise in a location that does not correspond to it’s original location
What may shoulder-tip pain indicate?
Diaphragmatic irritation
