When things go wrong in the respiratory system Flashcards
What do you use to measure airway resistance?
Forced expiratory volume in 1 sec (FEV1) by spirometry
What is FEV1 usually?
FEV1 is normally 80% of vital capacity (forced exhalation is usually about 80% of total exhalation)
What are the main features of Chronic Obstructive Pulmonary diseases (COPDs)?
- Narrowing of airways -> increased airway resistance
- Elastic recoil of lungs lost -> decreased outflow pressure
- Both lead to decreased FEV1
- Increased residual volume (RV) (air remaining in lungs after fully exhaled) -> appearance of chest over-inflation
What are the main COPD diseases?
- Chronic bronchitis – narrowing
- Emphysema – recoil
What is Chronic Bronchitis, how do you define it and what is it usually due to?
- Inflammation of the bronchi – mucus hypersecretion
- Due to: smoking (80%), environmental irritants
- Lasts: at least 3 consecutive months in 2 consecutive years
What happens in Chronic Bronchitis?
- Irritants cause inflammation in bronchi
- Abnormal mucus secretion
- Plugs airways
- Prone to infection
- Further inflammation
What is the result of chronic bronchitis?
Airway obstruction
Shortness of breath/ wheezing
Chest pain, chronic (productive – sputum) cough
What is the treatment for chronic bronchitis?
Stop smoking
Bronchodilators
Antibiotics
What is Acute bronchitis?
- Due to bacteria/ virus
- Lasts days/ weeks
What happens in Emphysema?
- Smoking -> neutrophils and macrophages release elastase -> elastase destroys alveolar walls -> emphysema
- In healthy tissues we have anti-proteases that neutralise elastase (alpha1 antitrypsin) but not in emphysema
- Genetic alpha 1 antitrypsin deficiency also leads to emphysema (2% COPD patients)
- See increased compliance significantly ABOVE normal
- Increased RV (residual volume) -> increased FRC (functional residual capacity): chronically over-inflated lung
- Air gets trapped in lungs
What are the symptoms of emphysema?
Shortness of breath on exertion
Hyperventilation
Expanded chest
What is used to treat emphysema?
- Enzyme supplements in alpha 1 antitrypsin deficiency
- Supplemental O2 can be given
- Lung transplant the best method of treatment
- but loss of alveoli is permanent and irreversible
What are the symptoms of asthma?
Increased airway resistance:
Bronchoconstriction
Oedema of airway mucosa
Mucus-secretion
What are the causes/ precipitating factors of asthma?
Hypersensitivity reaction to allergens Air pollution Exercise and cold air Emotional stress Genetics? Conflicting evidence with causes
What is the mechanism of asthma?
Mast cell activation -> histamine and cytokine release -> oedema, mucus, smooth muscle contraction - bronchoconstriction