Asthma Flashcards
What is Asthma?
Type 1 Hypersensitivity which causes reversible airway obstruction
List the proven risk factors for asthma?
- Atopy
- Occupation
- Smoking
Define atopy
An inherited tendency to produce IgE in response to allergen
What kind of conditions can becaused by atopy?
- Asthama
- Eczema
- Hayfever
- Food Allergies
How do we test for atopy?
- Markers
- Skin prick test (place allergen under skin)
- IgE tests
What kind of inheritance has the main effect on atopy?
MAternal inheritence is 3x as influential as paternal inheritance when it comes to determining atopy
What kind of genes show association with atopy?
- Immune response genes (Il-4, IL-5, IgE)
- Airway genes (ADAM33)
What sort of allergens are known to be related to asthma?
House dust mite dropppings
Cat allergens
How are exposure and atopy relateD?
Exposure doesnt cause atopy or asthma.
once someone atopic is sensitized to an allergen it can trigger an asthmatic response.
How much of asthma is occupational?
Around 10-15% of adult onset asthma is occupational
What types of occupations can cause asthma?
Bakers - Grains
Lab workers - Rodent urine
Painters - PAint
Chefs/fishermen - Crustaceans
What happens to a child whose mother smokes in pregnancY?
They can develop:
- Lower FEV1
- Wheezy illness
- A greater airway responsiveness
- Greater chance & severity of asthma
What is the grandmother effect?
A child will be twice as likely to develop asthma if their grandma smoked during pregnancy (it skips a generation).
Also 1.5x more likley if their mum did and 2.5 times if both did.
How are airway obstructions related to astgma?
Someone with a localized airway obstruction like a tumour or foreign body can appear to have asthma.
What symptoms are we looking for in a history to diagnose asthma?
- Wheeze
- Short of breath (dyspnoea)
- Chest tightness & pain
- Cough (paroxysmal, sudden)
- occasional sputum
Why is simply seeing the symptoms not enough to diagnose asthma?
Theyre the same symptoms as any other respiratory disease
What beyond the symptoms do we look for to diagnose asthma?
The variability of the symptoms. Only is asthma are the symptoms mixed up and variable with time/location.
What kind of variability is there in asthma symptoms?
The symptoms can be varied due to trigers like exercisem cold air, smoke, pets or a job.
They can also vary in time such as at day or night or weekends or holidays or even seasons.
What other conditions do we look for in a hisotry to denote asthma?
Other atopic conditions like eczema or hayfever
What do we look for in family and social history?
- Families atopic disease
- Smoking
- Pets
- Occupations
- Psychosocial stresses
What drugs can worsen asthma?
B-blockers
Aspirin
NSAIDS
What should we cheack if someone already has asthma?
Compliance and technique with inhalers
How useful is examination in asthma diagnosis?
Not much as theyre not always having symptoms.
Can rule out asthma sometimes if another conditions can be seen
What kind of investigations can we do to determine asthma?
- Spirometry
- Testing with treatment
- Pulmonary function tests
- Peak flow monitoring
- Specialist investigations
How is dynamic spirometry used?
An FEV1/FVC is taken during symptoms and if the ratio is abnormally low (<80%) this show a generalised airway obstruction
How do we use a pulmonary function test?
If an obstruction is found a full pulmonary function test is done which will rule out COPD/Emphysema
What makes up a full pulmonary function test?
- Lung volume is tested using gas trapping with helium which tells us Residual volume and Total lung capacity
- Gas transfer rate of Carbon Monoxide is used to determine that thers no tissue destruction.
How do we test with treatment?
If spirometry shows obstruction and pulmonary function tests rule out COPD/emphysema then a bronchodilator like salbutamol is used. Failing that a course of oral corticosteroids.
What do we use to determine occupational asthma?
Serial peak flow readings every 2 hours for atelast 5 days to see if symptoms worsen at work.
What kind of specialist investigations do we use?
- Airway responsiveness to methacholine
- Exhaled Nitric Oxide
What do we use a chest X-ray for?
A chest X-Ray excludes other conditions
What kind of parameters are used to measure asthma severity?
- Ability to speak
- How high the heart rate is
- How fast the respiratory rate is
- The PaO2 and SaO2
- Any impaired consciousness, confusion or exhaustion
What are the biggest indicators of asthma in a child?
- SOB @ rest
- Personal/parental hisotry of atopic illness
- Wheeze (not rattle or stridor)
- variable symptoms
- Much more in boys than girls
Why arnt peak flows and prick tests used in kids?
Too many kids have variable peak flows without asthma.
Lots of kids are allergic without having asthma as a symptom.
Moderate acute asthma in adults
Increasing symptoms;
Peak flow > 50-75% best or predicted;
No features of acute severe asthma.
Severe acute asthma in adults
Any of the following:
Peak flow 33-50% best or predicted;
Respiratory rate ≥ 25/min;
Heart rate ≥ 110/min;
Inability to complete sentences in one breath.
Life-threatening acute asthma in adults
Peak flow
Near-fatal acute asthma in adults
Raised PaCO2 and/or the need for mechanical ventilation with raised inflation pressures.
Moderate acute asthma in kids
Able to talk in sentences;
Arterial oxygen saturation (SpO2) ≥ 92%;
Peak flow ≥ 50% best or predicted;
Heart rate ≤ 140/minute in children aged 1–5 years; heart rate ≤ 125/minute in children aged over 5 years;
Respiratory rate ≤ 40/minute in children aged 1–5 years; respiratory rate ≤ 30/minute in children aged over 5 years.
Severe acute asthma in kids
Can’t complete sentences in one breath or too breathless to talk or feed;
SpO2 140/minute in children aged 1–5 years; heart rate > 125/minute in children aged over 5 years;
Respiratory rate > 40/minute in children aged 1–5 years; respiratory rate > 30/minute in children aged over 5 years.
Life-threatening acute asthma in kids
SpO2
