Asthma in Canada
About 8% of the population has asthma. (5-10% prevalence)
About 50% of people with asthma is poorly controlled.
Most Common Non-Communicable Pediatric Disease
It is the inverted pyramids.
10% of people with severe or uncontrolled asthma make up 54% of the cost spent on asthma. 70% of people with mild or controlled asthma make up only 13% of the cost.
If you can keep asthma under control, you will decrease cost.
Pathophysiology of Asthma
Early stage has to do with mast cells and constriction of the airways.
Late stage has to do with infiltrates of lymphocytes, neutrophils, and eosinophils.
Can cause inflammation and edema, mucus and plasma exudation, smooth muscle contraction, and epithelial damage/shedding.
Asthmatic airways often have increased vasculature, are inflamed, and are edematous. These result in a compromise in airspace lumen.
Correlation of Atopic Diseases
Asthma often correlates with other types of allergies. It os common to have overlap with allergic rhinitis and eczema.
If the patient has these, you want to get these under control first as they can be an excaberating factor.
Early and Late Asthmatic Response
Early phase is due to mast cell release.
Late phase is due to cellular infiltration.
Potential Asthma Triggers
Infections - particularly viral respiratory
Irritants - tobacco and air pollution, noxious chemicals, cold air/exercise
Allergens - cats, dogs, dust, aspergillus, suphites, MSG
Drugs - aspirin/NSAIDs, beta-blockers
Miscellaneous - strong emotional response
Clinical Presentation of Asthma
Variable wheezing, dyspnea, chest tightness, cough.
May be worse at night or in the morning.
Demonstrating Varible Airflow Obstruction
Spirometry: for adults - less than 75% FEV1 and an increase of 12% or more after a bronchodilator has been applied with more than 200mL of increase. For children, less than 80% with an increase of 12% with bronchodilator.
Patient is exposed to increasing concentrations of methacholine.
You are looking for a 20% drop in FEV1, and the concentration where FEV1 drops 20% is known as the PC20.
PC20 <4mg/mL - consistent with asthma
PC20 >16mg/mL not consistent with asthma
PC20 >4-16mg/mL is indeterminate
Diagnostic Testing for Asthma
Pulmonary function testing - spirometry/peak flow as well as methacholine challenge is useful to aid in diagnosis
CBC - may show eosinophilia
IgE level - may be elevated
Asthma vs. COPD
Age of onset - asthma may be at any age but tends to be younger, and most cases of COPD are in patients over the age of 50
Smoking Hx - asthma may or may not have, but COPD is almost invariably a current smoker or an ex-smoker
Cough - asthma is often nocturnal, while COPD is often in the morning
Wheeze & Dyspnea - asthma is usually episodic, while COPD is more gradual and progressive
Peak Flow - Reduced and variable in asthma, while it is usually reduced and consistent in COPD
Bronchodilator trial - asthma often shows an increase in FEV1 while COPD will usually have no change
Steroid trial - asthma shows a good response, and COPD shows minimal