Asthma and Mechanics of Breathing Flashcards
What are some things that can trigger asthma?
Cold air Infection (viral infections especially) Exercise Allergies Exposure to gases or fumes Emotional stress Hormones
What causes asthma
People who have very hypersenitive airways
The same response as normal, just exaggerated
A lot of mucus, coughing, bronchoconstriction, etc
2 functions of the pleural fluid
Reduce friction between the lungs and the thoracic wall
Create a negative pressure environment
Asthma
Episodic bronchoconstriction (from hyper-reactive bronchioles)
Severe dyspnea, coughing and wheezing
Asymptomatic between the attacks
Status asthmaticus may be fatal
Asthma tests and diagnosis
- Medical history
- Lung function (spirometry)
- Chest X-ray
- Lab tests on your blood and sputum
- Allergy testing: may worsen the asthma
In asthma, the inflammatory response involves what 3 cells?
Mast cells
T lymphocytes
Eosinophils
4 histological findings in asthma
Airway cellular infiltration
Epithelial disruption
Mucosal edema
Mucus plugging
Bronchial Asthma Histology
- Gross appearance (2)
- Histology (6)
- Overdistended lungs, mucus plus occlude bronchioles
- Thickened basement membrane, edema, inflammatory infiltrates, hyperplasia of submucosal glands and goblet cells, bronchial wall muscle hypertrophy, areas of denuded epithelium
Steps in the immediate immune response causing asthma
- Allergen enters
- Allergen binds to IgE on mast cells
- Mast cells degranulate, release inflammatory mediators and chemotactic factors
- Edema, bronchoconstriction and mucus hypersecretion occur
Steps in the delayed immune response causing asthma
- Decreased ciliary function and epithelial damage
- Afferent nerve discharge
- Efferent (vagal) nerve discharge)
- Mucus hypersecretion and bronchoconstriction
Bronchodilators are…
Long-acting beta2 agonists
How do long acting beta 2 agonists work?
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
How does the beta 2 adrenergic receptor work?
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
Corticosteroid/glucocorticoid hormones
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
Inspiration muscles
- Normal
- Exercise
- Diaphragm, external intercostal muscles
2. Scale muscles, sternocleidomastoids
Expiration muscles
- Normal
- Exercise
- Passive
- Internal intercostals
Abdominal muscles
Intrapulmonary pressure
Pressure in the alveoli
Rises and falls with breathing, but always equalizes with the atmospheric pressure
Intrapleural pressure
Pressure within the pleural cavity
Also fluctuates with breathing, but is always less than Palv
Transpulmonary pressure
Palv - Pip
Transmural pressure that governs the static properties of the lungs
2 major determinants of lung compliance
- The stretchability of the lung tissues
2. The surface tension at the air-water interfaces within the alveoli
What happens in pneumothorax?
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
3 factors affecting the mechanics of breathing
Airways resistance
Alveolar surface tension
Lung compliance
Surfactant
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
Spirometry
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
Functional residual capacity
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
Residual volume
The air that is in the respiratory zone to keep it open, and the air in the conducting zone
Cannot be measured by spirometry
FEV and FVCs for
- Obstructive diseases
- Restrictive diseases
- FVC and FEV1 are both much smaller than they should be, and the ratio is not 80% (less)
- FEV1 and FVC are reduced, but the ratio stays the same (no problem with exhaling, the problem is inhaling)
4 characteristics of obstructive disorders
Airflow limitation
Increased lung volume
Air trapping
Normal or increased air compliance
3 characteristics of restrictive diseases
Reduced lung volume
Increased lung stiffness (reduced compliance)
FEV1/FVC ratio is normal or increased
