respiratory Flashcards
define asthma:
common chronic inflammatory disorder of the airways characterised by reversible airflow limitation, airway hyperresponsiveness and bronchi inflammation
what is atopy?
genetic predisposition to IgE-mediated allergen sensitivity
atopic triad includes:
asthma
rhinitis
dermititis
what is the hygiene hypothesis?
epidemiology shows increased autoimmune and allergic responses in developed countries
reduced exposure to infectious pathogens at an early age predisposes individuals to such diseases
encourages Th2 predominant response ->IgE
patients with aspirin induced asthma commonly exhibit Samter’s triad, what is this?
asthma
aspirin sensitivity
nasal polyps
how are the different types of sensitisers of occupational induced asthma categorized?
low molecular weight
high molecular weight
how do low molecular weight compounds trigger asthma in occupational setting:
produce IgE mediated hypersensitivity response
the effects are immediate/soon after exposure
examples of low molecular weight triggers of asthma:
flour
latex
how do high molecular weight compounds trigger occupational asthma:
compounds develop a complex immune response after long term repeated exposure to the compound
examples of high molecular weight compounds which trigger asthma:
wood dust, isocyanates
what is the key to dx occupational asthma:
peak flow diaries used during periods of work and holiday
refer to specialist
what exposures contribute to exercise induced asthma:
cold air exposure
environmental pollutants
what is the pathophysiology of the early phase of asthma:
inhalation of allergens -> T1 hypersensitivity reaction immediately
sensitisation occurs during allergen exposure -> release of IgE Abs from plasma cells, which bind to mast cell receptors
subsequent exposure -> degranulation of mast cells and histamine release
->sm contraction, bronchoconstriction
inflammation -> airway obstruction
what is the pathophysiology of the late phase of asthma:
the initial early phase followed by:
recruitment of variety of inflammatory cells hours later (PMN cells, T cells)
more complex than early phase
B-agonists do not cause complete reversal
what is the pathophysiology of the chronicity of asthma:
response to persistent chronic inflammation
airways lay down fibrous tissue
remodeling occurs -> fixed airway obstruction, narrowing irreversible
what are the typical clinical features of asthma:
fine between attacks
sob, exp wheeze, cough
worse at night
what other signs of asthma may be present:
prolonged exp phase
tachypnoea
Harrison’s sulcus
what is a Harrison’s sulcus?
groove at inferior border of the ribcage seen in children with chronic severe asthma
also rickets
what are the clinical features of a severe asthma attack (acute)?
confused mental status
resp effort decreased
hypoxia
how is diagnosis of asthma investigated?
spirometry and PEFR
FVC?
forced vital capacity - exp
max exp following full insp
FEV1?
forced expiratory volume in 1 sec
what spirometry changes seen in obstructive picture?
FVC: N or reduced due to air trapping in bases
FEV1: reduced
REV1/FVC ratio: <70%
what is indicative of asthma on spirometry:
reversibility when bronchodilators used
12%