THE NATURE OF AIRWAY OBSTRUCTION Flashcards
what is asthma?
a hyperresponsiveness disorder that causes reversible airflow obstruction
what are the signs and symptoms of asthma?
chest tighness dyspnoea difficulty breathing wheezing cough
what are some triggers of asthma?
air pollution cigarette smoke dust pet dander cockroaches mold pollen medications such as aspirin and beta blockers
outline the steps of hypersensitisation of atopic asthma?
person is exposed to allergen
allergen is picked up by APC and presented to a T cell
T cell differentiates into Th2
Th2 releases IL4 to produce IgE and IL5 to activate eosinophils
IgE primes mast cells
when re-exposed to the allergen, IgE cross binds mast cells
this causes release of pro inflamamtory mediators to cause bronchoconstriction and eosinophil recruitement
what happens when we get chronic inflamamtion is asthma?
scarring
fibrosis
permenant narrowing of the airways
what is extrinsic asthma?
a type 1 hypersensitivity reaction triggered by extrinsic allergens
often affects indivisuald with atopic Fhx
what is intrinsic asthma?
non-immune
caused by viral infections, stress, exercise and smoking
why can NSAIDs trigger asthma?
as NSAIDs inhibit prostaglandin production which causes increased leukotriene production = smooth msucle contraction of airways
how do we diagnose asthma?
mainly from symptoms
then initiate treatment and assess response
can do spirometry , reversibility testing, mannitol challege testing, PEFR for 4 weeks
blood gases
what is reversibility testing?
spirometry is done without any inhaled therapy before test (have to be off short acting beta agonist for >4 hours and off long acting beta agonists for >15 hours).
You then administer a bronchodilator and repeat spirometry about 15 minutes later to see whether you have a significance improvement (FEV-1 increases by >12% indicates a significant difference)
what is the problem with reversibility testing?
asthma is episodic so you may find no response on some days
what is the mannitol challenege testing?
spurometry with inhaling increasiny concentrations of mannitol
at the point where FEV1 reduces by 15%, we consider this the concentration required to cause bronchial hyperresponsiveness to mannitol
how do we classify asthma?
with frequency of daytime and nighttime symptoms, FEV1 between exacerbation and the degree that asthma interferes with life
what is intermittent asthma?
<3 episodes of daytime symptoms in a week
<3 episodes of nightitime symptoms in a month
FEv1 >80% between exacerbations
no limitations
what is mild persistant asthma?
> 3 episodes of daytime symptoms in a week (but not every day)
3-4 episodes of nightitime symptoms in a month
FEv1 >80% between exacerbations
minor limitations
what is moderate perisstant asthma?
7 episodes of daytime symptoms in a week
1 or more episodes of nightitime symptoms in a week
FEv1 60-80% between exacerbations
moderate limitations
what is severe persistant asthma?
multiple episodes of daytime symptoms in a day
episodes of nightitime symptoms every night
FEv1 <60% between exacerbations
extreme limitations limitations
how do we treat intermittent asthma?
SABA as needed
how do we treat mild persistant asthma?
SABA as needed
daily low dose inhaled corticosteroid
how do we treat moderate persistant asthma?
SABA as needed
low dose inhaled corticosteroids daily
LABA
how do we treat severe persistant asthma?
SABA as needed
LABA
increased dose of inhaled corticosteroids
what happens if asthma isnt responsive to SABA, LABA or inhaled corticosteroids?
use systemic oral corticosteroids
why are systemic oral corticosteroids left to the last resort?
because of their adverse systemic effects e.g. osteoporosis, cataracts, hyperglycaemia, adrenal supression, fat redistribution
how do we characterise a life threatening asthma exacerbation?
PEFR <25% O2 sats <92 altered mental status absence of wheezing normal PaCO2
how do we treat a near fatal asthma exacerbation?
oxygen non-rebreater mask SABA with nebulizer or metered dose inhaler ipratropium bromide oral or IV systemic corticosteoids a
at what PEFR can a patient go home?
> 70%
what are some lifestyle changes to help with asthma?
smoking cessation
weight loss in overweight patients
breathing exercises
what is COPD?
a group of lung conditions that cause breathing difficulties. It includes chronic bronchitis and emphysema
what are the symptoms of COPD?
exertional breathlessness cough sputum production wheezing frequent chest infections
what are the signs of COPD?
patient sitting up, pursed lip breathing, using accessory muscles
barrel chest
loss of weight
percussion shows hyperresonance
outline how COPD can lead to cor pulmonate?
chronic hypoxemia causes hypoxic vasoconstriction which can cause pulmonary hypertension over time. This puts strain on the right side of the heart = failure
what are the 2 main signs of cor pulmonale?
JVP distention
peripheral oedema
hepatomegaly
whats the main risk factor for COPD?
smokng
what are COPD exacerbations?
acute worsening of symptoms
what are the 2 main types of COPD?
chronic bronchitis
emphysema
what is chronic bronchitis?
inflammation of the airways which increases mucus production, causes smooth muscle hypertrophy, golblet cell hyperplasia, etc
what are the symptoms of chronic bronchitis?
a continuous cough for >3 months a year for at least 2 consecutive years
phlegmy cough, wheeze, chest discomfort
what is emphysema?
an inflammatory response leading to excess elastases being produced which causes excessive destruction of alveolar cell walls
this causes a loss in elastin so a loss in elastic recoil = alveoli colapse when we exhale. air becomes trapped in alveoli causing them to puff up, impairing gas exchange
in people <45 who seeminly have COPD, what should you always consider?
alpha-1 antitrypsin deficiency
what is alpha 1 antitrypsin deficiency?
an autosomal dominant disorder where alpha-1 antitrypsin isnt exported out of the liver so it cannot inhibit elastase. Elastase therefore accumulates in the lung parenchyma, causing damage
enzyme accumulates in liver so may get liver cirrhosis
how do we diagnose COPD?
suspicion and relevant exposure
FEV1:FVC <70%
remeasure pulmonary function tests after giving an inhaled bronchodilator - results should be <12% change because its irreversible
how do we treat COPD?
smoking cessation oxygen broncodilators corticosteroids vaccines - dont want infections to trigger COPD excerbations
when giving oxygen in COPD, why do we aim for sats of 88-92%?
because we want to maintain a level of hypoxaemia as this is stimulating the respiratory drive
outline the differences between asthma and COPD?
COPD usually presents in >40s whilst asthma in childhood but can be any age
COPD is chronic and continuous whilst asthma varies with triggers
asthma patients will often have FHx of atopy
COPD patients will often have had exposure to cigarette smoke
changes are seen on an xray in COPD but not asthma
what drives the inflamamtion in asthma?
eosinophils
what drives the inflammation in COPD?
neutrophils
what is bronchiectasis?
An obstructive lung disease caused by chronic inflammation leading to bronchi and bronchiole damage and dilation. This inflammation causes mucus plugs to form in the airways and obstruct airflow.
what causes bronchiectasis?
CF severe pneumonia infection COPD asthma whooping cough TB fungal infections
outline the pathology of bronchiectasis?
chronic inflammation causes damage to ciliated epithelial cells and elastin fibres in airways. fibroblasts trying to repair the damage actually deposit more collagen, making the lungs less elastic and more stiff.
The stiff, mucus filled lungs make it diffiuclty for air to flow smoothly
what are the symptoms of bronchiectasis?
wheezing coughing SOB foul smelling mucus digital clubbing
how do we treat bronchiectasis?
treat the recurrent pneumonias with antiboitics and remove excess mucus with percussion or postural drainage
remove any physical obstructions
name some different types of asthma?
allergic asthma seasonal asthma occupational asthma non-allergic asthma exercise-induced asthma diffiuclt asthma severe asthma brittle asthma
what are curshmanns spirals?
mucus plugs that block air exchange and prevent inhaled medications from reaching the site of inflamamtion
seen in asthma
what are charcot leyden crystals?
crystals formed from the breakdown of eosinophils - seen in asthma
