Sensory aspects of respiratory disease Flashcards
Outline the prevalence of different respiratory symptoms
Cough Third most common complaint heard by GP 10-38% of patients in respiratory outpatients complain of cough Chest pain Most common pain for which patient seeks medical attention (35%), including acute chest pain Shortness of breath (SOB, dyspnea) 6-27% of general population 3% of visits to A&E
What is meant by symptoms of respiratory disease
SYMPTOMS
An abnormal or worrying sensation that leads the
person to seek medical attention
e.g. Cough
Chest pain
Shortness of breathWhat is meant by a physical sign of respiratory disease
PHYSICAL SIGN
An observable feature on physical examination
e.g. Hyperinflation of chest wall
Dullness on percussion of chest wall
Increased respiratory rate
Reduced movement of chest wall
Describe conscious sensation production
- The sensory stimulation (e.g. a cut) activates sensory transducers which transmit the signal via excitation of sensory nerves (afferent nerves into the CNS).
- CNS creates a sensory impression – neurophysiology.
a. This impression leads to the perception of information. - The brain interprets the information coming from sensory nerves and evokes a ‘sensation’ – behavioural psychology.
Describe the function of cough
A crucial defence mechanism protecting the lower respiratory tract from
inhaled foreign material
excessive mucous secretion
Usually secondary to mucociliary clearance
but important in lung disease when mucociliary function is impaired and mucous production is increased
Mucous reaches large airways- then you cough
Describe the expulsive phase of coughing
Inhaled material and material brought up the broncho-pulmonary tree to the trachea and larynx by mucocilliray clearance can trigger a cough reflex
This is caused by a reflex deep inspiration that increases intrathoracic pressure whilst the larynx is closed
The larynx is suddenly opened, producing a high-velocity jet of air, which ejects unwanted material at a high speed through the mouth
facilitated by bronchoconstriction and mucous secretion.
Describe the nerve profile in the airways
• Image on the left shows a nerve terminal on the surface of the epithelium • It is well placed to sense the external environment (e.g. by mechanical stimulation of the nerve terminal by dust) • This nerve terminal could respond by triggering a cough
Some on goblet cells- sensitive to mucus
Summarise the localisation of cough receptors
Rapidly adapting irritant receptors which are located within airway epithelium.
Most numerous on posterior wall of trachea,
At main carina, and branching points of large airways, less numerous in more distal airways. Absent beyond the respiratory bronchioles.
Also in the pharynx. Possibly also in the external auditory meatus, eardrums, paranasal sinuses, pharynx, diaphragm, pleura, pericardium, and stomach.
Stimuli: laryngeal and tracheobronchial receptors respond to chemical and mechanical stimuli.
Describe the different nerves involved
Vagus- stomach, trachea, bronchi, ear drums
Trigemminal- para nasal sinuses
Glossopharyngeal- larynx
Describe the different types of nerve fibres
§ Slow adapting stretch receptors. o Main stimulus is inflation. § Rapidly adapting stretch receptors. o Main stimulus is inflation. § C-fibre receptors. o Main stimulator is chemicals like capsaicin.
Describe C-fibres
C – fibre receptors
“free” nerve endings
Larynx, trachea, bronchi, lungs
Small unmyelinated fibres (C)
Chemical irritant stimuli, inflammatory mediators
Release neuropeptide inflammatory mediators Substance P, Neurokinin A, Calcitonin Gene Related peptide
Describe rapidly adapting stretch receptors
Rapidly adapting stretch receptors
Naso-pharynx, larynx, trachea, bronchi
Small, myelinated nerve fibres (A)
Mechanical, chemical irritant stimuli, inflammatory mediators
Describe slowly adapting stretch receptors
Slowly adapting stretch receptors Located in airways smooth muscle Myelinated nerve fibres Predominantly in trachea and main bronchi Mechanoreceptors Respond to lung inflation
What do all the sensory nerves in the airways pass through to reach the brain
ALL sensory nerves from the airway pass through the 10th cranial nerve, AKA the Vagus nerve.
Describe the experiments which demonstrated the functions of the different nerve fibres
• The above image shows measurements of the action potential, tracheal pressure (P) and arterial blood pressure (ABP) • Caspaicin has been given which is a stimulus to the sensory nerves • C-‐fibres are stimulated by CHEMICALS • The C-‐fibre is stimulated when the caspaicin is injected intravenously • The caspaicin has NO EFFECT on the rapidly and slow adapting stretch receptors • The MAIN STIMULUS for the rapidly and slow adapting stretch receptors is INFLATION • INCREASE in tracheal pressure = rapidly adapting stretch receptors STOP firing \+ slow adapting stretch receptors are STIMULATED to fire • These receptors are most likely to be involved in coughin
Distinguish between the stimuli for rapidly and slow adapting stretch receptors
o Hyperinflation (mechanical) stimulates a rapid response. o Hyperinflation (mechanical) stimulates a slow response.
Describe mechanoreceptors
o Activated by mechanical displacement and citric acid.
o Look like a tree.
Transmit vagus nerve afferents through nodose ganglion via myelinated A alpha fibres
Describe noicireceptors
o Activated by capsaicin, bradykinin, citric acid and cinnamaldehyde.
o TRPV1, TRPA1 and B2 channels are present.
Transmit vagus nerve afferents via unmyelinatec C-fibres through nodose ganglion
List some receptors involved in sensing mechanical and chemical changes
TRPV1: Transient receptor potential vanniloid-1 receptor
TRPA1: Transient receptor potential cation channel, subfamily A1
ASIC: Acid-sensing ion channel
B2: Bradykinin receptor B2
Describe the afferent neural pathways for cough
Stimulation of irritant receptors (RARs)/ Or cough receptor Mechanical (e.g. dust, mucous, food/drink)
Chemical
(e.g. noxious, intrinsic inflammatory agents)
stimulation of irritant receptors leads to firing down Vagus nerve to cough centre in medulla- superior laryngeal nerve joins from larynx
Some also sent to other parts of the cerebral cortex
Describe the efferent neural pathways for cough
Cerebral cortex communicates with medullary cough centre
Efferents sent to glottis (to close it)
Diaphragm, external intercostals and the accessory muscles of inspiration
Summarise the full neural pathway for cough
• Sensory information goes via the vagus nerve and through the brainstem to the cough centre • The cough centre consists of the nucleus tractus solitarius -‐ a collection of neurons that are connected to the medullary cough pattern generator • The reflex is probably a brainstem reflex Laz’s Notes Respiratory 108 • From the medullary cough pattern generator you get stimulation of various muscles needed to produce the cough • The complete cough pathways also includes the cerebral cortex • When you go to SLEEP, this reflex is INHIBITED so you need to be awake to a certain extent to be able to cough • Under general anaesthetic this is also suppressed
Outline the mechanics of coughing
• Inspiratory phase with negative flow during inhalation Glottic pressure in the minimum flow phase (glottis closes to generate pressure) Glottis opening Expiratory phase • The inspiratory phase opens up the trachea • During the act of coughing there is an increase in intrapulmonary pressure that compresses the posterior membrane of the trachea which pushes through and narrows the trachea into a crescent shape • This increases flow and contributes to the sound produced • NOTE: the brain is really active when you feel the need to cough
Describe the cough sound waveforms
2 phases with an initial explosive phase that is the first cough sound, followed by an intermediate phase with decreasing sound.
an additional third phase called voiced or glottal phase which gives rise to a second cough sound.
List some common causes of cough
§ Acute infection – e.g. bronchopneumonia, rhinovirus.
§ Chronic infection – e.g. CF or TB.
§ Airways disease – e.g. Asthma.
§ Parenchymal disease – e.g. Emphysema.
§ Tumours.
§ Foreign bodies.
§ Cardiovascular problems – e.g. Left ventricular failure.
§ Other disease – e.g. Recurrent aspiration, GERD.
§ Drugs – e.g. ACE inhibitors.
List the common types of acute cough (< 3 weeks)
Common cold: Cough Post nasal drip Throat clearing Nasal blockage Nasal discharge Rhinovirus most common cause- symptoms disappear after 2 weeks
List the causes of a chronic persistent cough
Asthma and eosinophilic-associated (25%) Gastro-oesophageal reflux (25%) Rhinosinusitis (postnasal drip) (20%) Chronic bronchitis (‘smoker’s cough) (8%) Bronchiectasis (5%) Drugs eg Angiotensin converting enzyme inhibitor (1%) Post-viral (3%) ‘Idiopathic’ (10%) Other causes (3%)
Describe Gastro-oesophageal reflux and cough: mechanisms
Oesophageal bronchial’ reflex (i)
Direct action of protons on cough receptors (ii)
Activation of brain stem
‘cough’ centers (iii) in NTS- efferents to respiratory muscles and cough
How does sputum change in infection
May become a yellowish or green colour
Summarise cough hypersensitivity syndrome
Irritation in the throat or upper chest
Cough paroxysms difficult to control (not throat clearing)
Triggers: Deep breath, laughing, talking too much,
vigorous exercise;
Smells (perfumes, vinegar)
Cigarette smoke
Eating crumbles (biscuits)
Cold air, changing temperatures
Lying flat
What is a chronic cough or cough hypersensitivity syndrome indicative of
Increased cough reflex
How can you measure the sensitivity of the cough reflex
Sensitivity of the cough reflex can be measured using caspaicin o Caspaicin is the thing in chilies that give them their hotness o You initially give a dilute solution of caspaicin and then increase the concentration until the participant coughs o Chronic coughers are particularly sensitive to caspaicin • Caspaicin an activate nociceptors through TRPV1 receptors
Describe the plasticity of neural mechanisms
Excitability of afferent nerves increased by chemical mediators eg prostaglandin E2
Increase in receptor numbers eg TRPV-1 (transient receptor potential vanniloid-1 or capsaicin receptor), voltage-gated channels
Neurotransmitter increase eg neurokinins
in brain stem
Describe TRPV-1
- Calcium-permeable, non-selective cation channel
- Activated by vanilloid ligands (eg capsaicin, endocannabinoid, noxious heat & H+); 12-lipoxygenase metabolites
- Expressed in sensory neurones of dorsal root and trigeminal ganglia
Expressed more in patients with a chronic cough
Summarise the mechanism of chronic cough
• There may also be an increase in inflammatory mediators, which damage or change the reactivity of the nerves to various stimuli like caspaicin • NOTE: this diagram shows that smooth muscle hypertrophy in asthma could affect the slowly adapting receptors that could contribute to enhanced hypersensitivity
Describe symptomatic suppressive therapy
Central action:
Opiates: Codeine, dihydrocodeine, pholcodeine,
Dextromethorphan, (Morphine, diamorphine)
Peripheral action:
Moguistine, levodopropizine,
Describe disease specific therapy
Eosinophil-associated: Inhaled corticosteroids
Gastro-oesophageal reflux disease: Proton pump inhibitors,
Histamine H2 antagonists
Post-nasal drip (rhinosinusitis): Topical steroids, antihistamines
Bronchiectasis: Postural drainage, Antibiotics
Summarise the use of antitussives
• If you are coughing excessively then you might want to suppress it but not completely eliminate the cough response because then you’d be getting rid of its defensive capabilities • Opiates can act as an antitussive but they are not particularly effective as they work at doses where there are a lot of side-‐effects (e.g. morphine and codeine)
Describe speech pathology management
↑voluntary control
↓ cough sensitivity
↓laryngeal irritation
↓laryngeal muscle contraction
Outline the locations of the different inputs
Nose
Trigeminal (V)
Pharynx
Glossopharyngeal (IX) Vagus (X
Larynx
Vagus (X)
Lungs
Vagus (X)
Chest wall
spinal nerves
Summarise the anatomical pathways of touch and pain
§ Touch and pain have slightly different pathways.
§ The main difference is at which level the pathways cross to the contra-lateral side:
o Touch – crosses at the caudal medulla.
o Pain – crosses at the same anatomical level, i.e. straight away.
§ Brown-Sequard Syndrome – hemisection of the left side of the spinal cord means touch will be fine but pain will be felt on the other side of the body.
As and Ab in touch pathway
Aalpha and C fibres in pain pathway
Describe the different types of pain
Visceral pain (from visceral organs eg heart, gi tract, bronchial wall) is not the same as somatic pain (from skin). Visceral pain is difficult to localise, diffuse in character and is referred to somatic structures. Number of visceral afferents is less than number of somatic afferents Pain arising from various viscera in the thoracic cavity and from the chest wall is often qualitatively similar and exhibits overlapping patterns of referral, localisation and quality, leading to difficulties in diagnosis.
Describe chest pain from the respiratory system
Pleuropulmonary disorders:
Pleural inflammation eg infection, pulmonary embolism,
Pneumothorax, malignancy eg mesothelioma
Tracheobronchitis:
Infections, inhalation of irritants
Inflammation or trauma to chest wall:
Rib fracture, Muscle injury, Malignancy, Herpes zoster (intercostal
Nerve pain)
Referred pain: shoulder-tip pain of diaphragmatic irritation
Describe the non-respiratory causes of chest pain
Cardiovascular disorders Myocardial ischaemia/infarction Pericarditis Dissecting aneurysm Aortic valve disease Gastrointestinal disorders Oesophageal rupture Gastrooesophageal reflux Cholecystitis Pancreatitis
‘Psychiatric disorders’
panic disorder
Self-inflicted
describe the brain regions involved in pain
Brain regions involved: 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 dyspnoea
Troublesome shortness of breath reported by a patient
Occurs at inappropriately low levels of exertion, and limits exercise tolerance
Unpleasant and frightening experience. Can be associated with feelings of impending suffocation
Poor perception of respiratory symptoms and dyspnea may be life-threatening
What are the different scales for dyspnoea
see tables
Describe descriptions related to air hunger
Hunger for more air Urge to breathe more Starved for air Suffocation or smothering Short of breath Breaths feel too small
Describe symptoms associated with work/effort
Breathing requires effort Breathing requires work Breathing is uncomfortable Feels like heavy exercise Size of breaths feel too large
Describe symptoms associated with tightness
Tightness/constriction in chest
Heaviness in my chest
Describe the different methods for assessing shortness of breath and dyspnoea
Volunteered comments & clinicians’ assessment Subjective rating scales Visual analogue Modified Borg Questionnaires Exercise tolerance related Eg. Baseline Dyspnea Index, Shortness of Breath Questionnaire Quality of life Eg. SF36, St George’s Respiratory Questionnaire Exercise testing 6 minute walk test Shuttle test
List some disorders presenting with chronic SOB or dyspnoea
Impaired pulmonary function
Airflow obstruction eg Asthma, COPD, tracheal stenosis
Restriction of lung mechanics eg idiopathic pulmonary fibrosis
Extrathoracic pulmonary restriction eg Kyphoscoliosis, pleural effusion
Neuromuscular weakness eg Phrenic nerve paralysis
Gas exchange abnormalities eg Right to left shunts
Impaired cardiovascular function
Myocardial disease leading to heart failure
Valvular disease
Pericardial disease
Pulmonary vascular disease
Congenital vascular disease
Altered central ventilatory drive or perception
Systemic or metabolic disease
Metabolic acidosis
Anaemia
Physiologic processes eg deconditioning, hypoxic high altitude, pregnancy, severe exercise
Idiopathic hyperventilation
Summarise the general treatment of dyspnoea
Treat the cause (eg lung or cardiac)
Treatment of dyspnea itself is difficult
Therapeutic options:
Add bronchodilators eg anticholinergics or b-adrenergic agonists
Drugs affecting brain eg morphine, diazepam
Lung resection (eg lung volume reduction surgery)
Pulmonary rehabilitation (improve general fitness, general health, psychological well-being)
