Asthma Flashcards
What is asthma?
Inflammatory disorder of the airways characterized by airway hyperresponsiveness, airflow obstruction, and clinical symptoms i.e. wheezing, trouble breathing
What happens to the bronchial wall in asthma?
Mucus in airway, mucosal edema, increased mucous glands, contracted/hypertrophied muscle
What happnes to the flow volume loop in asthma?
Maximal flow decreases & curve becomes concave – lower flow at a given time
Is the airflow obstruction reversible in asthma? What reverses it?
Yes! Inhaled bronchodilator imroves it
What happens to gas exchange in asthma- both between attacks & during attacks?
Between = normal
During = V/Q mismatch –> hypoxemia
- typically mild, can be very severe
What happens to alveolar ventilation during an asthma attack?
Increased minute ventilation –> alveolar hyperventilation
If it’s a severe attack, you can get resp musc fatigue/ increased dead space –> alveolar hypoventilation
What are the symptoms of asthma?
Episodic dz
Between attacks, symptoms vary depending on asthma control
Nocturnal symptoms are common
During attacks: wheeze, cough, chest tightness
What is the differential for wheezing?
Upper airway obstruction
Lower airway obstruction:
- Asthma
- COPD
- CF, bronchiectasis
- Large obstruction i.e. tumor, stenosis, foreign body
- Bronchiolitis
- Pulm edema
- Carcinoid syndrome
What are the causes of asthma?
Genetic
Environment: hygiene hypothesis
Prenatal environment
Diet
Which things are believed to be protective against asthma?
Older sibs
Lack of vaccination
Early life resp infection
Parasitic infection
Day care
Gut microflora
Animal exposure
Drinking unpasteurized milk
Barn in 1st year of life
Bacterial endotoxin
What can trigger asthma?
Allergens
Viruses: influenza = biggest trigger for severe, rhinovirus most common trigger for all asthma
School: bc associated with resp tract infect
Immunological mechanism of allergic sensitization:
1st exposure:
Pollen finds antigen presenting cell
APC finds a proallergic Th2 cell
Th2 starts making cytokines
Cytokines reach B cell and tell it to become a mast cell specific to the allergen
Upon reexposure:
Mast cell binds antigen –> release of mediator –> immediate rxn
Cytokines tell eosinophil to do a late phase rxn
IgE’s cause releas of inflammatory mediators. Which ones?
Immediate: granule contents- histamine, TNF-alpha, proteases, heparin
Minutes: lipid mediators i.e. PG’s LT’s
Hours: cytokines
What are the subgroups of asthma?
Airway remodeling: 2ndary to inflammation –> inflammation, mucus hypersecretion, subepithelial fibrosis, airway smooth muscle hypertrophy, angiogenesis
Occupational asthma: can be allergic type (IgE mediated) or non-allergic type (irritant induced)
Exercise-induced: probably related to cold, dry air
Targeted treatment of asthma
