Lung Disease Types Quiz

Study Notes

The primary clinical division of lung disease is obstructive and restrictive lung disease.
Obstructive lung disease is characterized by difficulty expiring air. Examples include:
- Bronchial asthma
- Chronic bronchitis and emphysema
- Bronchiectasis
- Bronchiolitis
Key features of obstructive lung disease include:
- Bronchial narrowing
- Destruction of elastic tissue
- Inspiration is minimally affected, but expiration is difficult, leading to air trapping and a "barrel chest" appearance.
- Tidal volume may be normal
- Inspiratory reserve volume (IRV) and expiratory reserve volume (ERV) are low
- Total lung capacity (TLC) is high
- Vital capacity (VC) is reduced
Restrictive lung disease is characterized by difficulty expanding the lungs to take in air. Examples of restrictive lung disease include:
- Lung causes:
  - Lung fibrosis (can be caused by autoimmune disease, drug-induced, occupational exposures, or be idiopathic - unknown cause)
  - Pneumonia
  - Acute respiratory distress syndrome (ARDS)
- Non-lung causes:
  - Chest wall deformities
  - Abdominal problems
  - Neurological causes like diaphragm paralysis
  - Respiratory center depression
  - Idiopathic causes
Key features of restrictive lung disease include:
- Something restricts the lungs' ability to expand.
- Inspiration is difficult and involves small, rapid breaths.
- Tidal volume may be normal
- IRV and ERV are low
- Residual volume (RV) is low
- TLC is low
- VC is low

Respiratory failure is defined as a condition where PaO2 is below 60 mmHg while breathing room air or PaCO2 is above 50 mmHg.
Respiratory failure represents the failure of oxygenation and carbon dioxide elimination.
Respiratory failure can be acute or chronic.
Respiratory failure can be categorized into Type 1 or Type 2.

Type 1 respiratory failure (hypoxemic respiratory failure) is characterized by a PaO2 < 60 mmHg with a normal or low PaCO2.
Type 1 respiratory failure is often associated with acute lung diseases such as:
- Pulmonary edema (cardiogenic or non-cardiogenic)
- ARDS
- Pneumonia
- Pulmonary hemorrhage
- Lung collapse
Type 2 respiratory failure (hypercapnic respiratory failure) is characterized by a PaCO2 > 50 mmHg.
Type 2 respiratory failure is often associated with:
- Drug overdose
- Neuromuscular disease
- Chest wall deformity
- Chronic Obstructive Pulmonary Disease (COPD)
- Bronchial Asthma

Acute respiratory failure develops over minutes to hours, with a rapid decrease in pH to 45 mmHg. This is due to respiratory pump failure or increased carbon dioxide production. Depending on the cause, PaO2 may be normal or decreased.
Chronic respiratory failure develops over days, with an increase in bicarbonate level (HCO3).

The respiratory pump consists of the chest wall, pulmonary parenchyma, muscles of respiration, and the central and peripheral nervous systems.
Type 2 respiratory failure is caused by a failure of this respiratory pump to ventilate effectively.

pH: 7.35-7.45
- ↓pH indicates acidosis
- ↑pH indicates alkalosis
PaO2: >70 mmHg
- ↓PaO2 indicates hypoxemia
PaCO2: 35-45 mmHg
- ↑PaCO2 indicates hypercapnia
HCO3: 22-28 mmol/l
- ↓pH + ↑PaCO2 indicates respiratory acidosis
- ↑pH + ↓PaCO2 indicates respiratory alkalosis
- ↑HCO3 indicates metabolic alkalosis
- ↓HCO3 indicates metabolic acidosis