Internal Medicine (Theory) · MU Sofia

11. Acute and chronic respiratory failure;

Explains respiratory failure as impaired gas exchange causing hypoxaemia and sometimes hypercapnia, then lists its causes grouped by site, from airway and pulmonary circulation to brain, chest wall and pleura. Covers a restrictive, obstructive, mixed and acute/chronic classification, symptoms, and a table of physical examination findings from dyspnoea patterns to cyanosis and polycythaemia signs. Ends with laboratory changes and spirometry and blood gas criteria for diagnosis.

Inside: 8 sections · 3 labelled pictures · 1 table · 15 flashcards · 3 min

Topic 10 of 58 in the MU Sofia syllabus for Internal Medicine (Theory) (Medicine, Year 3). The free AceMed note covers it in 8 sections, about 351 words (3 min of reading), with 15 flashcards.

In this note

  1. Acute and Chronic Respiratory Failure
  2. Definition
  3. Etiology
  4. Classification
  5. Symptoms
  6. Physical Examination Findings
  7. Lab Tests
  8. Instrumental Tests

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:

  1. 1. Decreased Airflow in/out of lungs
  • Physical obstructions: foreign bodies, tumors
  • Decreased Breathing ability: sedatives, CNS depressants
  • Chest abnormalities: deformities, trauma
  1. 2. Impaired lung blood supply
  • Thromboembolism (like PE)
  • Reduced Right heart output: Right-sided HF, certain MIs
  1. 3. Poor gas exchange in lung tissue
  • Damage to alveoli affects O₂-CO₂ exchange
  • Common causes:
  • Infections (e.g., pneumonia)
  • Interstitial lung disease
  • Pulmonary edema
  1. 4. Respiratory center damage in brain
  • Intracranial hemorrhage, infarction, tumors
  • Severe metabolic alkalosis
  • Drug intoxications: morphine, barbiturates, benzodiazepines
  1. 5. Chest wall or muscle dysfunction
  • Spinal or rib trauma, diaphragm injury
  • Neuromuscular disorders:
  • Myasthenia gravis
  • Muscular dystrophy
  • Ascending paresis (Landry’s)
  1. 6. Pleural diseases
  • Air/fluid in pleura: pneumothorax, hydrothorax, hemothorax, pleuritis
  • Severe pulmonary fibrosis (esp. after TB or purulent pleuritis)

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