Asthma. SS Visser, Lung Unit, UP. Contents. Definition Disease Pattern Prevalence Mortality Etiology Pathogenesis Triggers of acute attacks. Contents. Pathophysiology Manifestations of Resp failure Diagnosis: clinical,physiologic,immunologic and radiologic Differential diagnosis
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SS Visser, Lung Unit, UP
Sx more severe & persistent
Nocturnal early awakening with dyspnea
diurnal fluctuation in lung function
Unstable lung function
BD response, therapeutic needs
1.Early bronchospastic response- type1reaction
within min after IH of AG:
Mechanism: IH of aeroallergensensitizatiom formation of IgE & expression on mast cells re-exposure to AG mast cell degranulation & mediator release bronchospasm
2.Late-bronchospastic reaction: in 30-50%, 6-10 hours after AG exposure. Minority only a late response
Mechanism: recruitment of E, N, L and macro-phagesrelease lipid mediators(PG E2, F2 ,D2; LT C,D,E , PAF), O2radicals, toxic granule proteins, cytokines (TH1:IL-2, IFN; TH2: IL-4, IL-5) bronchoconstriction, vascular congestion, mucosal edema, mucus production, mucociliary transport.
Destruction of AW epithelium by toxic granule contentsepithelial shedding into bronchial lumen exposure of sensory nerve endings and imbalance in cholinergic and peptidergic neuronal control AW remodelling with subendothelial fibrosis, goblet cell hyperplasia, smooth muscle hyper- trophy, vascular changes fixed AW obstruction.
Pharmacol stimuli such as aspirin, NSAIDS, - adrenergic blockers, preservatives,col agent
Environment pollution- ozone, SO2, NO2
Occupational- metal salts, biol enzymes
Infection- resp viruses
Exercise –IH cold dry airthermally-induced hyperemia and micro-vascular engorgement
Emotional stressTriggers of acute asthmatic episodes
(a) Exercise: A 15% drop in FEV1 post exercise indicates exercise induced asthma.
(b) Metacholine challenge: A 20% reduction in FEV1 at Metacholine concentrations < 8mg/ml indicates bronchial hyperreactivity.
This is expressed as a PC20 value of eg 0.5mg/ml (= a 20% reduction in FEV1 at 0.5mg/ml Metacholine).
1. Immediate Rx: O2 40-60% via mask or cannula + 2 agonist (salbutamol 5mg) via nebulizer + Prednisone tab 30-60mg and/or hydrocortisone 200mg IV. With life-threatening features add 0.5mg ipratropium to nebulized 2 agonist + Aminophyllin 250mg IV over 20 min orsalbutamol 250ug over 10 min.
2. Subsequent Rx: Nebulized 2 agonist 6 hourly + Prednisone 30-60mg daily or hydrocortisone 200mg 6 hourly IV + 40-60% O2.