When Things Go Wrong In The Respiratory System Flashcards
What is the primary focus of obstructive respiratory diseases?
Conditions which impede the rate of flow into and out of the lungs.
What are the main types of respiratory diseases?
- Obstructive
- Restrictive
- Infection & inflammation
What is a key characteristic of obstructive respiratory disease?
Increased airway resistance (due to narrowing of airways)
Outflow pressure reduced (due to loss of elastic recoil in the lungs = can’t exhale as much air)
What does reduced compliance in restrictive lung disease indicate?
Decreased lung volume and reduced vital capacity (VC)
What is Forced Expiratory Volume in 1 second (FEV1)?
A measure of airway resistance using spirometry.
What percentage of vital capacity does FEV1 normally represent?
Approximately 80%.
What are the two main diseases classified under Chronic Obstructive Pulmonary Disease (COPD)?
- Chronic bronchitis (narrowing of airways)
- Emphysema (loss of recoil)
What is the global impact of COPD as of 2021?
Approximately 3.5 million deaths globally (5% of all global deaths).
4th leading cause of deaths worldwide
What is the primary cause of chronic bronchitis?
Due to smoking (80% of time) and environmental irritants
How long must chronic bronchitis last to be diagnosed?
At least 3 consecutive months in 2 consecutive years.
What are common treatments for chronic bronchitis?
- Stop smoking
- Bronchodilators (opens airways)
- Antibiotics
What is the mechanism of damage in emphysema?
- smoking
- neutrophils & macrophages release elastase
- elastase destroys alveolar walls (so poor gas exchange)
- emphysema is developed
Elastase normally inactivated by a1 antitrypsin
Genetic a1 antitrypsin deficiency (in 2% of COPD patients) also causes emphysema as elastase is secreted
What is are significant symptoms of emphysema?
Shortness of breath on exertion
Hyperventilation (to remove CO2)
Expanded chest
What is the main treatment for asthma?
- Short term = Bronchodilators e.g. salbutamol reliever inhaler (B2 adrenoreceptor antagonists = work against bronchoconstriction)
- Long term = Anti-inflammatories e.g. preventer inhaler (for mild to medium asthma)
What are the key causes of asthma?
- Hypersensitivity to allergens
- Air pollution
- Exercise and cold air
- Emotional stress
- Genetics?
What is the primary characteristic of restrictive lung disease?
Decreased lung compliance.
What is a common cause of intrinsic restrictive lung disease?
Long-term exposure to dust (e.g., pneumoconiosis)
Drugs (e.g. methotrexate)
Rheumatoid arthritis (inflammatory condition)
ARDS & IRDS
Or may be idiopathic (no cause, just develops)
What is the effect of fibrosis on lung compliance?
It causes a decrease in lung compliance.
What are upper respiratory tract infections commonly caused by?
Minor infections such as the common cold.
What bacterium is commonly responsible for pneumonia?
- Streptococcus pneumoniae
- Staphylococcus aureus
- Klebsiella pneumoniae
What is tuberculosis caused by?
Inhalation of Mycobacterium tuberculosis.
Highly contagious
What are the two phases of tuberculosis?
- Latent - asymptomatic, non-infectious, granuloma in lung tissue
- Active - spreads to bronchioles and circulation = becomes contagious
What is the primary target of the COVID-19 virus?
Lung epithelial cells.
What receptor does SARS-CoV-2 bind to for infection?
Angiotensin-converting enzyme 2 (ACE2) receptor.
What is the significance of the Omicron variant of COVID-19?
It represented over 98% of sequenced samples as of February 2022.
What is a common misconception about COVID-19 vaccines?
Vaccines are only for high-risk groups.
What is the average number of upper respiratory tract infections an adult experiences per year?
2-4 URTI/year.
What is COPD characterised by?
- Narrowing of airways —> increases airway resistance
- Elastic recoil of lungs is lost —> reduced outflow pressure
- Thus decreased FEV1
- Increased residual volume (RV) —> appearance of chest over-inflation (due to retention of air)
What causes bronchitis?
Inflammation of the bronchi - mucus hypersecretion
What causes acute bronchitis?
Bacteria/ virus
Lasts days/ weeks
What happens in chronic bronchitis?
- irritants cause inflammation in bronchi
- abnormal mucus secretion (causes inflammation)
- plugs airways
- prone to infection
- further inflammation
What are symptoms of chronic bronchitis?
- airway obstruction
- shortness of breath / wheezing (due to obstruction)
- chest pain, chronic cough (in attempt to clear airway of mucus)
What happens to compliance in emphysema?
Significantly above normal
SO
Increased residual volume (RV) —> increased functional residual capacity (FRC) = chronically over-inflated lung
What causes emphysema?
20% of smokers develop COPD
Lifelong smokers
Loss of alveoli is permanent and irreversible
Treatment:
- stop smoking
- supplement O2
- lung transplant
- enzyme supplements in a1 antitrypsin deficiency
What are the symptoms of asthma?
- Bronchconstriction
- Oedema of airway mucosa
- Mucus secretion
All these increase airway resistance
What is the mechanism of asthma?
- Mast cell activation
- Histamine (causes allergic response) and cytokine (causes inflammation) release
- Oedema, mucus, smooth muscle contraction = bronchoconstriction
What is extrinsic cause of restrictive lung disease?
Non-muscular disease of upper thorax
What is fibrosis in restrictive lung disease?
Fibrosis is development of excess connective tissue
- Alveoli are replaced by fibrotic tissue = harden & become stiffer
- Decreased lung compliance
- Irreversible decrease in oxygen diffusion capacity
What causes fibrosis?
- Inhaled environmental and occupational pollutants
- Cigarette smoke
- Autoimmune disease
No effective treatments for fibrosis
What are respiratory tract infections caused by?
Upper respiratory tract infections
- common but minor
- average adult has 2-4 URTI/year
Lower respiratory tract infections
- less common but serious
- e.g. bronchitis, pneumonia, tuberculosis…
How does pneumonia affect the lungs?
- Affects bronchi and alveoli
- Inflammatory exudate (liquid) fills alveoli
- Leads to ‘consolidation’
- Lung tissues become firm and airless
Describe the mechanism of tuberculosis
- Replicate in alveolar macrophage
- This is know as Ghon focus = site of primary infection (latent phase)
- Initial infection has ineffective immune response
- Bacteria moved to lymph nodes so can spread to the body
- Collagen deposited around bacteria = can break down lung structure
- Lymph nodes erode releasing bacteria into: bronchioles or blood vessels
- Destruction of alveoli
Treatment of tuberculosis is difficult due to antibiotic resistance
