Airflow obstruction Flashcards
Diagnosis of airflow obstruction is done using a
Spirometer
Shape of obstructive in a flow diagram:
Can see a ‘dent’
Shape of restrictive in a flow diagram:
Smaller/all reduced
Normal FEV1/FVC
> 75%
Abnormal FEV1/FVC
<70%
Why might an airway be narrowed?
Mucus
Hypertrophy of bronchial smooth muscle
Breakdown of alveolar walls so airways collapse
Ex of conditions in which airway is obstructed by mucus:
Infection (acute bronchitis)
Chronic bronchitis
Ex of condition in which bronchial smooth muscle hypertrophies
Asthma
COPD
Ex of condition in which alveolar walls break down
Emphysema
Asthma is an example of what time of hypersensitivity reaction?
Type 1
Asthma is reversible/irreversible
Reversible
What does ‘reversible airflow obstruction’ mean?
Reversible with time or bronchodilators
Asthma is characterised by:
- Reversible
- Airway inflammation
- Hyperactivity of airway
Airway hyperactivity =
Increased tendency to spasm
How to diagnose asthma:
Hx - should be variable airway narrowing (bad periods which are self-limiting)
- Demonstrate variability using PF monitoring/bronchodilator reversibility studies/treatment trials
What increase of FEV1 in response to a bronchodilator is diagnostic of asthma?
> 15%
Bronchial hyperreactivty study =
Give a substance like histamine, mannitol etc.
Measure drop in FEV1
What kind of variation does peak flow have?
Diurnal
What can be given to an asthmatic to help them recognise exacerbations or when they need to use treatment?
Peak flow monitor
How can we find eosinophilia?
- Sputum eosinophila
- measure exhaled NO
Exhaled NO is a marker for
Eosinic airway inflammation
FENO =
Fraction exhaled nirtic oxide
Triggers for asthma:
Dust Air pollution Pet dander Foods: peanuts, wheat Chemicals Pollen Mould
What dominate asthmatic inflammation?
Th2 cells
eosinophils
Th1 t cells
promote cell immunity
IgG
Th2 cells
Enhance mast cells, eosinophils and IgE
What type of immunoglobulin to Th2 cells stimualte the production of
IgE
Name some cytokines released by Th2
IL-4
IL-5
IL-4 =
IgE
Mast cells
Mast cells release
Histamine
Leukotrienes
Prostaglandin
IL-5 =
Eosinophils
Eosinophils release
Histamine
Leukotrienes
“A genetic tendency to develop allergic diseases” =
Atopy
3 conditions a person with atopy is likely to develop
Asthma
Allergic rhinitis
Atopic dermatitis
What are drug developers now interested which attract eosinophils to the airways?
IL-5
Acute airway change in asthma =
Smooth muscle contraction Sensory nerve action Mucus hypersectrion Plasma leakage Oedema Inflammatory infiltrate
Chronic airway changes in asthma:
Subepithelial fibrosis
Smooth muscle hypertrophy
Chronic airway changes occur when
Asthma is ongoing, untreated, cannot be suppressed
2 conditions under the COPD umbrella:
Chronic bronchitis
Emphysema
In comparison to asthma, COPD is
Non-reversible
Doesn’t respond to bronchodilators/steroids
Doesn’t markedly change
Air becomes what in COPD
Trapped
What increases in COPD?
Expiatory residual volume/ total lung capacity
Emphysema is based on … Chronic bronchitis is based on ….
Emphysema = structural changes
Chronic bronchitis = clinical symptoms
What happens in emphysema
Alveoli are damaged, elastin broken down
Lose elasticity, enlarge
Septa breakdown
Difficult for lungs to recoil - collapse on expiration
What causes the breakdown of elastin in emphysema?
Inflammatory reaction - release leukotrienes, IL-8, TNF-a and proteases
What usually stops airways collapsing in expiration?
Elastic recoil/elastin
Most common pattern of emphysema associated with smoking =
Centrilobar
Panacinar emphysema is associated with =
Alpha-1 antitrypsin deficiency
What is alphae 1-antritrypsin?
A protease inhibitor which protects alveoli from unintended collateral damage from macrophages
What can happen with a paraseptal emphysema?
Pneumothorax
What can be seen on imaging in emphysema?
Bollous
Bollous =
Presence of abnormally large air space surrounded by relatively normal lung tissue
Chronic bronchitis definition:
Productive cough for at least 3 months/year for 2 consecutive years
What happens in chronic bronchitis?
Mucus gland hypertrophy Goblet cell hyperplasia Smooth muscle hypertrophy Inflammatory cells infiltrate Excess mucus
What inflammatory cells are involved in chronic bronchitis?
Neutrophils and lymphocytes
risk factors for COPD:
Smoking Occupational Passive smoke/cannabis Chronic asthma Biofules Familial (alpha 1 antitrypsin deficiency)
What is released by alveolar macrophages to clean up debris?
Proteases
Blue bloaters =
Chronic bronchitis
Pink puffers =
Emphysema
Shape of chest in emphysema can be
Barelled - due to air trapping
V/Q < 1 =
Perfusion is higher than ventilation
What can happen when perfusion is higher than ventilation?
pO2 falls
pCo2 increases
Pulmonary vasoconstriction
Consequences of pulmonary vasocontriction
Pulmonary hypertension –> cor pulmonale
Cor pulmonale =
Right sided heart failure
What happens in bronchiectasis?
Bronchial dilation
Chronic sputum production
What does cronchiectasis increase?
Infections
What does bronchiectasis resemble clinically?
COPD
Asthma
