General
- Definition: inability of the respiratory system to effectively carry out oxygenation and ventilation
- Two categories: Hypoxemic Respiratory Failure & Hypercapnic Respiratory Failure
- Hypoxemic Respiratory Failure = PaO₂ < 55 mmHg
- Hypercapnic Respiratory Failure = PaCO₂ > 45 mmHg
- Both categories can be acute or chronic
- Signs and symptoms of Acute Respiratory Failure
- Anxiety
- Accessory muscle use
- Diaphoresis
- After critical levels of hypoxemia and hypercapnia → encephalopathy & comatose
- Physical exam → respiratory distress 2/2 trying to overcome hypoxemia and hypercapnia → increased work of breathing
- Signs and symptoms of Chronic Respiratory Failure
- No signs of suffering
- Chronically low PaO₂ → polycythemia
- Chronically high PaCO₂ → Metabolic Alkalosis
- Certain situations warrant the consideration of mixed states
- e.g. acute hypoxemia in the setting of chronic hypercapnia → pneumonia in someone with advanced emphysema
- In this patient, when they become acutely hypoxic, they will hyperventilate to increase PaO₂
- By hyperventilating, they will remove some CO₂ and therefore this will cause a pseudo-normalization of the PaCO₂
- This pseudo-normalization will accentuate the alkalosis
- Therefore in someone with hypoxia with unexplained metabolic alkalosis, consider underlying chronic lung disease
- e.g. acute hypoxemia in the setting of chronic hypercapnia → pneumonia in someone with advanced emphysema
- Other causes of respiratory failure
- Upper Airway Obstruction
- Those that mimic respiratory failure by increasing sensations of dyspnea or inducing tachypnea
- Metabolic Acidosis
- Panic attacks
- Anxiety
- Vocal Cord Dysfunction
Evaluation of Respiratory Distress
Topics
10.1.1. Hypoxemic Respiratory Failure
10.1.2. Hypercapnic Respiratory Failure