Asthma Flashcards
What is asthma?
A chronic inflammatory condition of the airway
Recurrent episodes of dyspnoea, cough and wheeze caused by airway obstruction
What are the 3 characteristics/features of asthma?
Airflow limitation
Airway hyper-responsiveness to stimuli
Inflammation of the bronchi
Is the airway obstruction in asthma reversible?
Yes, usually
How is asthma classified?
Two categories.
Extrinsic: atopic
- allergens can be identified that are triggering the asthma
Intrinsic:
- no definite external cause
- many of these patients are atopic however
When do extrinsic and intrinsic asthma patients usually present?
Extrinsic: childhood
Intrinsic: middle age
Is there a genetic influence in asthma?
If so, which genes?
Yes
Often in genes involved in sensing pathogens
What is atopy?
Syndrome where people develop IgE antibodies against common environmental antigens such as dust, pollen
Atopic people have one or more of:
- Asthma
- Eczema
- Hayfever
What 3 features cause airway narrowing in asthma?
- Bronchial muscle contraction triggered by stimuli
- Mucosal swelling and inflammation
- Increased mucus production
In an asthma attack it is harder for the person to breathe in than to breathe out.
True or false?
False
It is harder for the person to breathe out that breathe in
Resulting in hyperinflation of the lung
How does the lung become hyper-inflated? And what happens when this happens?
In an acute asthma attack it is harder for the person to breathe in than out so the lungs become over filled.
No new air can get in or out so the blood does not receive enough oxygen
What happens to the smooth muscle in the airways in asthma?
Inappropriate and excessive contraction, constricting the airways
Hypertrophy and proliferation of the smooth muscle cells, making the airways narrower
What happens to the epithelial cells in the airways in asthma?
Metaplasia
Loss of ciliated columnar cells
An increase in the number of goblet cells
Increased basement membrane thickening
What do goblet cells do?
Secrete mucus
What is the role of antigen presenting cells (dendritic cells) in asthma?
They digest antigens of the allergen and present it to the lymphocytes which then cause inflammation
When the lymphocytes have been triggered by being presented with an antigen, what do they do?
They release cytokines (interleukins mainly) which activate and summon mast cells and eosinophils
These continue the immune response causing inflammation
What is the progression from encountering some pollen to developing asthma?
Inhale pollen
APCs present antigen to lymphocytes
Immune response occurs
Memory response is formed to the allergen, mediated by IgE
Immune system is now sensitised to the antigen
Everytime the person inhales pollen with this antigen again an immune response will occur
What is the role of mast cells in asthma?
They are summoned to the site by lymphocytes (that had been activated by APCs)
Antibodies produced by B cell bind to the mast cells and cause them to degranulate
When mast cells degranulate they release inflammatory mediators such as cytokines and histamine
What is the role of B cells in asthma?
They produce antibodies against the antigen
Theses then go on to activate mast cells to degranulate
What does histamine do?
Increases the permeability of the capillaries to white blood cells and some proteins
This allows them to engage with pathogen/allergen in the affected tissues
Causes an inflammatory response
What is eosinophilic asthma?
A type of asthma that involves eosinophils
Too many eosinophils are produced in the bone marrow
Too many eosinophils are recruited to the airways
In eosinophilic asthma, what causes greater numbers of eosinophils to be produced in the bone marrow?
Interleukin 5
In eosinophilic asthma, what causes greater numbers of eosinophils to be recruited to the airways?
Chemokines
Prostaglandin 2
What is the role of eosinophils in asthma?
They contribute to airway remodelling and tissue damage
What is non-eosinophilic asthma?
No eosinophils are involved
Could be neutrophils instead
What are the phenotypes of asthma?
Eosinophilic
Non-eosinophilic
List some causes of asthma attacks?
Cold air Exercise Emotion Allergens Infection (especially viral) Smoking Pollution NSAIDs B-blockers
How do asthma patients present?
Intermittent symptoms
Wheeze Cough SOB Chest tightness Sputum production
When are asthma patients’ symptoms usually worse?
At night, usually about 4am
What are the 3 Royal College of Physicians questions to ask an asthma patient?
Any recent nocturnal waking?
Usual asthma symptoms in the day?
Interference with activities of daily living
What should you ask an asthma patient during a GP consultation?
Age of onset
Did they have respiratory problems in childhood?
Do they have signs of atopy: eczema, Hayfever
Diurnal variation: worse in early hours of morning?
Disturbed sleep
Exercise tolerance
What is their environment? Any pets, dusty carpet, feather pillows
What is their job? Any allergens there, and do symptoms reduce when they are not at work?
Family history
What are the signs of chronic asthma?
Tachypnoea
Audible wheeze (polyphonic)
Hyper-inflated chest
Reduced air entry
What are the signs of a severe asthma attack?
Inability to complete sentences
Pulse over 110bpm
Resps over 25/min
Peak flow 33-50% of predicted
What are the signs of a life threatening attack?
What about near fatal?
Peak flow < 33%
SpO2 < 92%
PaO2 < 8kPa
Silent chest Reduced GCS Exhaustion = poor resp effort Cyanosis Hypotension
Near fatal = PaCO2 raised
What are the signs of a moderate asthma attack?
Peak flow over 50% of predicted
No signs of severe asthma
How do you distinguish asthma from COPD?
COPD:
Later onset and usually smoking related
Relentless, progressive SOB + wheeze
Less diurnal and day-to-day variation
Investigations for asthma.
Blood: eosinophils, O2 + CO2 stats
Tests for atopy: skin prick tests
CXR: exclude infection or pneumothorax
Oxygen saturations
Lung function tests:
- Peak flow
- Spirometry
- (Response to a challenge agent)
- Reversibility testing
What information can you get from spirometry?
FEV1 + FVC
What is FEV1?
Forced expiratory volume in 1 second
What is FVC?
Forced vital capacity: total amount of air exhaled during FEV test (all 3 seconds of exhalation)
What challenge agents are used in the response to a challenge agent test?
Mannitol: a bronchial irritant
Methacholine: a bronchoconstrictor
What is a response to challenge agent test?
What does it help diagnose
Airways are irritated and you watch what happens to the person
Helps diagnose exercise triggered asthma
What is reversibility testing?
Looks to see if there is an increase in lung capacity with bronchodilators or anti-inflammatory treatment
What is the differential diagnosis of wheeze, SOB, cough, etc.
Pulmonary oedema
COPD
Airway obstruction: tumour, foreign body
Pneumothorax
Pulmonary embolism
Bronchiectasis
Which asthmatics are at risk of death?
Those on at least 3 classes of treatment
Recent admission/frequent hospital attendance
Previous near fatal disease
Brittle asthma
Psychosocial factors
What is Brittle asthma?
Type of asthma where they get recurrent, severe attacks
Treatment of chronic asthma?
Avoid triggers
Use peak flow meter every day
Educate in case of emergency
Step up + down drug treatment:
- SABA
- SABA + LD ICS
- SABA + LD ICS + LTRA
- SABA + LD ICS + (LTRA if helpful) + LABA
- SABA + (LTRA) + MART (with LD ICS)
- SABA + (LTRA) + MART (with MD ICS)
- SABA + (LTRA) + HD ICS + LAMA/theophylline + REFER
Which oral steroid is usually used?
Prednisolone
Which inhaled steroid is usually used?
Beclometasone
Management of an acute asthma attack.
Salbutamol nebulised with oxygen
Prednisolone
Monitor O2 stats, heart and resp rate
Admit to ICE/HDU if in need of ventilation
What is the red-flag sign that you need to quickly admit to ITU/HDU and ventilate the patient?
Raised CO2 levels
