Asthma Flashcards
Does asthma improve with age?
Yes, 30-70% of children are markedly improved or asymptomatic by early adulthood
Causes of airflow obstruction in asthma
Acute bronchoconstriction, mucus plugging of airways, bronchial wall edema, inflammatory cell infiltration, airways wall remodeling (fibrosis), smooth muscle hypertrophy
Flow euqation
Q=(Change in P * πr^4)/ 8nL
How does radial traction keep airways open?
On inflation, lung parenchyma pulls open airways like spokes on a wheel.
Do airways stay open or do they close on inspiration?
They close slightly because of positive pleural pressure
What FEV/FVC ratio defines obstruction?
<0.7, Can reverse with bronchodilator
What is air trapping and what are the consequences?
Because of bronchoconstriction, some air remains trapped in alveoli. Therefore, residual volume grows and vital capacity shrinks.
Is increased airway resistance uniformly distributed in the lung?
No, some airways affected more than others
Effect of asthma on V/Q
V/q mismatch causes hypoxemia. Perfusion does decrease due to hypoxia-induced vasoconstriction, but it doesnt happen perfectly.
What happens to pACO2 during a mild asthma attack?
It actually falls, the reason why is unclear
What happens to PACO2 during a severe asthma attack?
It increases, made worse by respiratory muscle fatigue
Pulsus paradoxus in asthma
Systemic arterial pressure falls by more than 10mmHg during inspiration due to large swings in pleural pressure. Increased RV return causes decreased LV preload, also increased pulmonary capacitance reduces LV preload. Increased LV afterload because negative thoracic pressure.
Asthma phenotypes
Allergic (atopic) asthma
Non-allergic (nonatopic) asthma
Aspirin-exacerbated respiratory disease
Exercise-induced asthma
Or by pathology:
Eosinophilic
Neutrophilic
Pauci-granulocytic
Does allergic asthma have a genetic component?
yes. Strong family history correlation
How does an allergic asthma reaction happen?
Allergen inhalation, causes eosinophil reaction and TH2 response, which causes the production of IgE. IgE’s cross link on mast cells then degranulate next time the antigen is encountered.
Late phase of allergic asthma reaction?
Occurs due to the recruitment of additional inflammatory cells like basophils and neutrophils.
Asthma pathology
Cellular infiltrates and edema within the bronchial wall. Epithelial damage. Smooth muscle layer hypertrophy and hyperplasia. Basement membrane thickening. Increased number of goblet cells and mucous gland hypertrophy
Hygiene hypothesis
Exposure to infections early in like causes the development of TH1 mediated response and shifts the balance away from TH2.
TH2 Cytokines
IL4 cause IgE synthesis in B cells
IL5 causes eosinophil maturation
IL-9 mediated mast cell recruitment and function
IL-13 causes airway hyperresponsiveness and mucous hypersecretion
Exercise induced asthma
Pathogenesis seems to involve cooling of the airway. High energy water molecules evaporate and lead to cooling. This causes bronchoconstriction.
Aspirin-Exacerbated respiratory disease
Aspirin inhibits COX, which shifts the pathway to the production of Leukotrienes in the lipoxygenase pathway. Leukotrienes C4/D4/E4 cause bronchospasm/congestion/mucous plugging.
Samter’s triad
Asthma
Aspirin sensitivity
Nasal polyps
Airway remodeling
Consists of smooth muscle mass increase, mucous secretion increase, persistence of inflammatory cells, collegen depositon, reduced elasticity of airway wall.
Signs of asthma
Wheezing, prolonged expiratory phase
