Respiratory Flashcards
What is asthma?
a chronic inflammatory airway disease characterised by reversible, intermittent airway obstruction and hyper-reactivity
What makes up the atopic triad?
Asthma
Hayfever
Eczema
What is occupational asthma?
asthma caused by environmental triggers in the workplace
What is the aetiology of asthma and when does it typically present?
gentic predispostion + environmental trigger
typically presents in childhood but can be adult onset
What are the main features of asthma?
Episodic + diurnal variability: symptoms fluctuate at different times of the day, typically worse at night
SOB
Chest tightness
Dry cough
Wheeze
should improve with bronchodilators
may have family hx or hx of eczema, hay fever, food allergies
What are some potential triggers for asthma?
- Infection
- Nighttime or early morning
- Exercise
- Animals
- Cold, damp or dusty air
- Strong emotions
- Beta-blockers, NSAIDs
What are the risk factors for asthma?
family hx
allergens/irritants
atopic disease hx
cigarette smoking/ vaping
respiratory viral infection early in life
nasal polyposis
low socioeconomic status
What is the pathophysiology of an asthma exacerbation?
Early phase
- Excess of T helper 2 cells (type 2 inflammation)
- TH2 cells produce IL4, IL13 and IL5
- IL4+13 cause plasma cells to release IgE which activate mast cell degranulation
- Histamine, leukotriene and prostaglandins (T1 hypersensitivity reaction)
- Bronchospasm, increased mucus production and oedema Late phase
- More inflammatory cells recruited from blood (chemotaxis)
- Second phase of exacerbation
What are some of the long term consequences of asthma?
subepithelial fibrosis
basement membrane thickening
hypertrophy of smooth muscle cells
larger volume of mucus
increased vascularity
What is the forced expiratory volume in 1 second (FEV1) spirometry test and what does it measure?
the air a person can forcefully exhale in 1 second.
This measures how easily air can flow out of the lungs.
It is reduced with airflow obstruction
What is reversibility testing?
involves giving a bronchodilator (e.g., salbutamol) before repeating the spirometry to see if this impacts the results
What is the FEV1/FVC ratio for obstructive lung disease?
FEV1:FVC ratio of less than 70%.
person may have a relatively good lung volume, but air can only move slowly in and out of the lungs due to obstruction
What are FEV1 and FVC like in restrictive airway disease?
FEV1 and FVC are equally reduced
FEV1:FVC ratio greater than 70%
What is restrictive lung disease?
limits the ability of the lungs to expand and fill with air.
The lungs are restricted from effectively expanding
Difference in spirometry for restrictive and obstructive?
a low FVC indicates restrictive lung disease
a low FEV1:FVC ratio (under 70%) indicates obstructive lung disease
What does peak flow measure?
measures the “peak”, or fastest point, of the expiratory flow of air
a simple way of demonstrating how much obstruction to airflow is present in the lungs
and how well a condition such as asthma is controlled
What is PaO2?
partial pressure of oxygen, the amount of oxygen dissolved in the blood.
A low PaO2 indicates hypoxia.
What is FiO2?
fraction of inhaled oxygen.
Room air has an FiO2 of 21%, meaning the oxygen conc in room air is 21%
What investigations should be done for a patient presenting with suspected asthma?
Spirometry: FEV1/FVC ratio <70%
BDR test (reversibility): improvement in FEV₁ of 12% or more in response to beta agonists
peak expiratory flow rate (PEFR)
FeNO
CXR
FBC with differential
What are some differentials for asthma?
COPD
Chronic rhinosinusitis
CHF
Bronchiectasis
CF
What is the first-line management of asthma?
Short-acting beta agonist: salbutamol inhaled: (100 micrograms/dose inhaler) 100-200 micrograms inhaled up to four times daily – as needed, reliever
What can be used in the management of asthma if a SABA isn’t effective alone?
- Inhaled corticosteroid (ICS) beclometasone
- Long-acting beta 2 agonist (formoterol) inhaled + ICS
- Leukotriene receptor antagonists (montelukast)
- Long acting muscarinic antagonists, e.g. tiotropium
How do beta-2 adrenergic receptor agonists work?
bronchodilators
Adrenalin acts on the smooth muscle of the airways to cause relaxation
Stimulating the adrenalin receptors dilates the bronchioles and reverses the bronchoconstriction present in asthma
SABAs work for a few hours, e.g. salbutamol
How do inhaled corticosteroids work?
reduce the inflammation and reactivity of the airways.
These are used as maintenance or preventer medications to control symptoms long-term and are taken regularly, even when well.