January 19, 2016 - Asthma: Cellular

Question 1

Prevalence of Asthma

Answer 1

Is a very common condition. About 10% of the population has the disease.

57% of people with the disease have it poorly controlled.

Question 2

Characteristics of Asthma

Answer 2

1. Variable airflow obstruction
2. Airway hyperresponsiveness
3. Chronic airway inflammation

Question 3

Variable Airway Obstruction

Answer 3

Spirometry is critical in the assessment of respiratory disorders, including asthma.

You should never diagnose asthma without measuring spiromery or lung function. There are many people who have been diagnosed with asthma that do not actually have the disease.

Normal people have a FEV1/FVC volume of >80%, but in asthma this is below 70-75% because of the smaller, constricted airway.

Question 4

FVC in Asthmatic Patients

Answer 4

Forced vital capacity will be the same (or close to) in asthmatics compared to regular people, but it will take them longer to get there because the airway is smaller.

Question 5

Airflow Reversibility

Answer 5

When you administer a bronchodilator to asthmatic patients, they tend to have a marked improvement in their FEV1/FVC ratio.

Patients suffering form other respiratory diseases such as COPD does not show a marked change.

Question 6

Risk Factors for Developing Severe Asthma

Answer 6

Genetic factors (not just one gene)

Environmental factors (allergens, infections - Baker’s asthma is classic)

Host factors (defect in airway epithelium, obesity, etc.)

Triggers (viral infection, allergen exposure)

Question 7

Early and Late Response

Answer 7

After early exposure to the allergen or trigger, there is a marked decrease in FEV1 as there is an immediate response from cells in the immune system.

Hours later, the histamine and leukotrienes that were dumped in the area act as chemoattractants and initiate an inflammatory response which causes another marked decrease in FEV1 hours later.

Question 8

Airway Hyperresponsiveness

Answer 8

We can measure the amount of methacholine that is required to induce a 20% fall in FEV1. This concentration is known as the PC20.

If the PC20 is 4, you clearly have asthma. If the PC20 is between 4 and 16, you may have mild asthma, and if the PC20 is >16, you are normal.

Question 9

Asthma Sputum Cell Counts

Answer 9

It is normal to have ~2% eosinophils in the sputum.

In patients with severe asthma this number can rise as high as 50%.

Question 10

Inhaled Corticosteroids (ICS)

Answer 10

Asthmatic symptoms are sensitive to ICS treatment.

Smoking blunts the effects of ICS.

Question 11

Bronchial Thermoplasty

Answer 11

A treatment for severe asthma approved by the FDA in 2010 involving the delivery of controlled, therapeutic radiofrequency energy to the airway wall, thus heating the tissue and reducing the amount of smooth muscle present in the airway wall. This acts to stop the constriction of the smooth muscle and help alleviate asthmatic symptoms

Appears to be safe in the long term.