Asthma and Mechanics of Breathing

Question 1

What are some things that can trigger asthma?

Answer 1

Cold air
Infection (viral infections especially)
Exercise
Allergies
Exposure to gases or fumes
Emotional stress
Hormones

Question 2

What causes asthma

Answer 2

People who have very hypersenitive airways
The same response as normal, just exaggerated
A lot of mucus, coughing, bronchoconstriction, etc

Question 3

2 functions of the pleural fluid

Answer 3

Reduce friction between the lungs and the thoracic wall

Create a negative pressure environment

Question 4

Asthma

Answer 4

Episodic bronchoconstriction (from hyper-reactive bronchioles)
Severe dyspnea, coughing and wheezing
Asymptomatic between the attacks
Status asthmaticus may be fatal

Question 5

Asthma tests and diagnosis

Answer 5

1. Medical history
2. Lung function (spirometry)
3. Chest X-ray
4. Lab tests on your blood and sputum
5. Allergy testing: may worsen the asthma

Question 6

In asthma, the inflammatory response involves what 3 cells?

Answer 6

Mast cells
T lymphocytes
Eosinophils

Question 7

4 histological findings in asthma

Answer 7

Airway cellular infiltration
Epithelial disruption
Mucosal edema
Mucus plugging

Question 8

Bronchial Asthma Histology

1. Gross appearance (2)
2. Histology (6)

Answer 8

1. Overdistended lungs, mucus plus occlude bronchioles
2. Thickened basement membrane, edema, inflammatory infiltrates, hyperplasia of submucosal glands and goblet cells, bronchial wall muscle hypertrophy, areas of denuded epithelium

Question 9

Steps in the immediate immune response causing asthma

Answer 9

1. Allergen enters
2. Allergen binds to IgE on mast cells
3. Mast cells degranulate, release inflammatory mediators and chemotactic factors
4. Edema, bronchoconstriction and mucus hypersecretion occur

Question 10

Steps in the delayed immune response causing asthma

Answer 10

1. Decreased ciliary function and epithelial damage
2. Afferent nerve discharge
3. Efferent (vagal) nerve discharge)
4. Mucus hypersecretion and bronchoconstriction

Question 11

Bronchodilators are…

Answer 11

Long-acting beta2 agonists

Question 12

How do long acting beta 2 agonists work?

Answer 12

They improve the effects of inhaled corticosteroids given in combination
Inhalation limits the effects to the airways, minimizing the risk of systemic side effects
Fast acting mechanism, lasts a few hours

Question 13

How does the beta 2 adrenergic receptor work?

Answer 13

It is a GPCR
Causes cAMP production
Inhibits the release of pro-inflammatory mediators from mast cells
Bronchial smooth muscle relaxation in bronchioles walls
Dilation of the airways = decreased resistance to airflow and increased ventilation

Question 14

Corticosteroid/glucocorticoid hormones

Answer 14

Regulate gene expression
Take longer
Bind to the cytosolic glucocorticoid receptors of lung epithelial cells, complex translocated into the nucleus and targets promoters on inflammatory genes, regulates gene expression
Reduce or inhibit the production and secretion of pro-inflammatory mediators

Question 15

Inspiration muscles

1. Normal
2. Exercise

Answer 15

1. Diaphragm, external intercostal muscles

2. Scale muscles, sternocleidomastoids

Question 16

Expiration muscles

1. Normal
2. Exercise

Answer 16

1. Passive
2. Internal intercostals
   Abdominal muscles

Question 17

Intrapulmonary pressure

Answer 17

Pressure in the alveoli

Rises and falls with breathing, but always equalizes with the atmospheric pressure

Question 18

Intrapleural pressure

Answer 18

Pressure within the pleural cavity

Also fluctuates with breathing, but is always less than Palv

Question 19

Transpulmonary pressure

Answer 19

Palv - Pip

Transmural pressure that governs the static properties of the lungs

Question 20

2 major determinants of lung compliance

Answer 20

1. The stretchability of the lung tissues

2. The surface tension at the air-water interfaces within the alveoli

Question 21

What happens in pneumothorax?

Answer 21

Puncture of the pleural space
It has negative pressure so air flows in
Lung collapses
Have to reinflate the lung by positive pressure or recreate the negative pressure by removing the air

Question 22

3 factors affecting the mechanics of breathing

Answer 22

Airways resistance
Alveolar surface tension
Lung compliance

Question 23

Surfactant

Answer 23

Increases lung compliance by reducing surface tension and thus collapsing pressure
Normally it prevents alveolar collapsing
Produced by type 2 alveolar cells lining the alveoli and the smallest bronchioles
Mixture of phospholipids composed of DPPC

Question 24

Spirometry

Answer 24

Way to test your breathing
Measures how much air you can blow out of your lungs
How fast and how much air you breathe out

Question 25

Functional residual capacity

Answer 25

The volume of air left in the lungs at the end of a passive breath
The opposing forces of the chest wall and the lungs are in equ

Question 26

Residual volume

Answer 26

The air that is in the respiratory zone to keep it open, and the air in the conducting zone
Cannot be measured by spirometry

Question 27

FEV and FVCs for

1. Obstructive diseases
2. Restrictive diseases

Answer 27

1. FVC and FEV1 are both much smaller than they should be, and the ratio is not 80% (less)
2. FEV1 and FVC are reduced, but the ratio stays the same (no problem with exhaling, the problem is inhaling)

Question 28

4 characteristics of obstructive disorders

Answer 28

Airflow limitation
Increased lung volume
Air trapping
Normal or increased air compliance

Question 29

3 characteristics of restrictive diseases

Answer 29

Reduced lung volume
Increased lung stiffness (reduced compliance)
FEV1/FVC ratio is normal or increased