Definition
Respiratory failure = Inadequate or impaired gas exchange which leads to:
- Hypoxemia = ↓ O₂ in blood
- ± Hypercapnia = ↑ CO₂
This happens when the lungs can't properly oxygenate blood or remove CO₂.
Etiology
Conditions that may cause respiratory failure:
- Decreased Airflow in/out of lungs
- Physical obstructions: foreign bodies, tumors
- Decreased Breathing ability: sedatives, CNS depressants
- Chest abnormalities: deformities, trauma
- Impaired lung blood supply
- Thromboembolism (like PE)
- Reduced Right heart output: Right-sided HF, certain MIs
- Poor gas exchange in lung tissue
- Damage to alveoli affects O₂-CO₂ exchange
- Common causes:
- Infections (e.g., pneumonia)
- Interstitial lung disease
- Pulmonary edema
- Respiratory center damage in brain
- Intracranial hemorrhage, infarction, tumors
- Severe metabolic alkalosis
- Drug intoxications: morphine, barbiturates, benzodiazepines
- Chest wall or muscle dysfunction
- Spinal or rib trauma, diaphragm injury
- Neuromuscular disorders:
- Myasthenia gravis
- Muscular dystrophy
- Ascending paresis (Landry’s)
- Pleural diseases
- Air/fluid in pleura: pneumothorax, hydrothorax, hemothorax, pleuritis
- Severe pulmonary fibrosis (esp. after TB or purulent pleuritis)