Respiratory: Asthma - Diagnosis Flashcards
Define asthma [1]
A chronic inflammatory airway disease that causes a combination of cough, wheeze or breathlessness with
variable airflow obstruction
What are the 5 phenotypes of asthma? [5]
◦ Allergic asthma
◦ Non-allergic asthma
◦ Adult-onset (late-onset) asthma
◦ Asthma with persistent airflow limitation
◦ Asthma with obesity
Describe the difference in cells found in the phlegm of allergic and non-allergic asthma [2]
◦ Allergic asthma: eosinophilic
◦ Non-allergic asthma: neutrophilic
Which type of asthma is hard to treat with corticosteroids / difficult to treat patients?
◦ Allergic asthma
◦ Non-allergic asthma
◦ Adult-onset (late-onset) asthma
◦ Asthma with persistent airflow limitation
◦ Asthma with obesity
◦ Allergic asthma
◦ Non-allergic asthma
◦ Adult-onset (late-onset) asthma
◦ Asthma with persistent airflow limitation
◦ Asthma with obesity
Which of the following is most likely to be due to occupational environment?
◦ Allergic asthma
◦ Non-allergic asthma
◦ Adult-onset (late-onset) asthma
◦ Asthma with persistent airflow limitation
◦ Asthma with obesity
Which of the following is most likely to be due to occupational environment?
◦ Allergic asthma
◦ Non-allergic asthma
◦ Adult-onset (late-onset) asthma
◦ Asthma with persistent airflow limitation
◦ Asthma with obesity
Explain which part of the lung is most commonly affected in asthma? [1]
Terminal bronchioles: surrounded by smooth muscle
Which type of hypersensitivty is asthma? [1]
Type 1
Describe the pathway that causes asthma [5]
i. Allergen picked up by dendritic cells and presented by MHC Class II molecules
ii. CD4 cells activate the TH-2 lymphocytes through the release of IL4, IL5, IL13.
iII. IL 4 leads to the production of IgE antibodies: coat mast cells and stimulate degranulation and the release histamines, leukotrienes and prostaglandins
iv. IL-5 activates eosinophils: causes more cytokine & leukotrienes release
v IL-9 = mast cell proliferation
Describe the pathophysiology of asthma
Airway inflammation:
- Immune cells activated by TH2, mast cells and eosinophils
- Causes pro-inflam mediators (cytokines, chemokines, histamines, leukotrines) to cause airway oedema, mucus production, and bronchoconstriction
Bronchoconstriction
- narrowing of the airways and obstruction of airflow.
Airway hyperresponsiveness
- airways exhibit excessive narrowing in response to various stimuli, such as allergens, irritants, and cold air
- mediated by several factors, including the release of inflammatory mediators, increased airway smooth muscle contractility, and impaired bronchodilator mechanisms
Mucus production and airway remodeling:
* Chronic inflammation causes airway remodeling
* Subepithelial fibrosis, increased smooth muscle mass, mucus gland hypertrophy, and angiogenesis.
A number of patients with asthma are sensitive to which drug? [1]
Patients who are most sensitive to asthma often suffer from []? [1]
A number of patients with asthma are sensitive to aspirin.
Patients who are most sensitive to asthma often suffer from nasal polyps. Remember the nose is part of the respiratory tract from a histological point of view.
What are the classical features of asthma? [4]
What helps to create a clinical picture regarding features and treatment? [1]
episodic symptoms; typically worse at night:
* widespread, polyphonic expiratory wheeze (occurs from turbulent airflow in narrow airways)
* breathlessness
* chest tightness: airway obstruction and increasde work of breathing
* cough: dry or productive; worse at night or early in morning.
Symptoms should improve with bronchodilators. No response to bronchodilators reduces the likelihood of asthma.
TOM TIP: A localised monophonic wheeze is not asthma.
Give the top differentials of a localised wheeze [3]
Inhaled foreign body
tumour
a thick sticky mucus plug obstructing an airway (pneumonia)
pulmonary oedema
A chest x-ray is the next step.
Which drugs can worsen asthma? [3]
Non-selective beta blockers: propranolol
- blocking the beta receptors in the lungs, which leads to bronchoconstriction and breathing difficulties.
Non-steroidal anti-inflammatory drugs: aspirin, ibuprofen or naproxen
- This reaction is known as aspirin-exacerbated respiratory disease (AERD) or aspirin-induced asthma.
Which cells are responsible for the acute phase of asthma? [1]
Which cells are responsible for the late phase of asthma? [3]
Early: mast cells
Late: Th2 helper cells –> B cells –> IgE & Eiosinophils
What’s the difference between asthmas that are considered extrinsic, intrinsic and occupational? [1]
Extrinsic asthma is caused by:
- Air pollution
- Allergens
- Maternal smoking
- Genetics
- More responsive to steroid tx
Intrinsic asthma is:
- non-allergic
- Less responsive to steroids
- Colds / infections can trigger
Occupational
- Allergens at work
Don’t learn too muc detial
Describe the diagnostic pathway for asthma
There is no signal diagnostic test
Describe the features that would make you suspicious that a patient has asthma [6]
More than one of the following in episodes:
wheeze
breathlessness
chest tightness
cough
diurnal variability
Triggered by allergen, exercise, cold air, aspirin or β-blocker
Atopic features
Eczema
Hayfever
Fx
Low PEFR or FEV (note: both decrease with age)
Describe the features that would make you less suspicious that a patient has asthma [6]
Dizziness, light-headedness or peripheral tingling
Productive cough in the absence of wheeze or breathlessness
Repeatedly normal examination when breathless
V oice disturbance
Symptoms only with colds
Significant smoking history (>20 pack years)
Cardiac disease
Normal PEF or FEV1when symptomatic
Describe the diagnostic pathway for diagnosis of asthma
- Clinical suspicion based off clinical assessment (history, exam, previous medical records)
- IF high probabilty of asthma:
Code as suspected asthma and start treatment
Assess response to treatment:
Good response = asthma;
poor response then intermediate probability of asthma. - Next: Test for airway obstruction using spirometry and bronchodilator reversibility:
-
Test for variability by investigating:
Reversibility
PEF charting
Challenge tests -
Test for eosinophilic inflammation:
FeNO
Blood eosinophs
Skin prick test, IgEIf good response: asthma
If poor response: investigate other more likely diagnosis
BTS pathway
What does FeNO test? [1]
What level of FeNO would be considered positive for asthma in adults? [1]
What level of FeNO would warrent further consideration for asthma positive for asthma in adults? [1]
What level of FeNO would you consider a different diagnosis than asthma in adults? [1]
fractional exhaled nitric oxide (FeNO):
FeNO tests the amount of NO produced by iNOS, which is raised in eisinophils (which are raised in asthma)
- in adults a level of >= 40 parts per billion (ppb) is considered positive
- 25-39 ppb would warrant further investigations
- < 25 ppb would be a different diagnosis
What level of FeNO would be considered positive for asthma in children? [1]
- in children a level of >= 35 parts per billion (ppb) is considered positive
What spirometry result would be considered obstuctive for asthma? [1]
FEV1/FVC ratio less than 70% (or below the lower limit of normal if this value is available) is considered obstructive (e.g., asthma or COPD).
What would indicate positive reversibility testing in adults [2] and children [1]?
Reversibility testing:
- in adults, a positive test is indicated by an improvement in FEV1 of 12% or more and increase in volume of 200 ml or more
- in children, a positive test is indicated by an improvement in FEV1 of 12% or more
Describe what is meant by direct bronchial challenge testing [1]
What results would indicate a positive result for asthma? [1]
Direct bronchial challenge testing is the opposite of reversibility testing.
Inhaled histamine or methacholine is used to stimulate bronchoconstriction, reducing the FEV1 in patients with asthma.
NICE say a PC20 (provocation concentration of methacholine causing a 20% reduction in FEV1) of 8 mg/ml or less is a positive test result.
