hypercapneic respiratory failure

Introduction

acute & chronic forms

Etiology

• COPD
• asthma
• restrictive lung disease
  • chest wall musculoskeletal disorders
  • obesity
• depressed respiratory drive
  • opioids
  • sedatives

Pathology

• alveolar ventilation is inadequate resulting in an increase in pCO2
• since blood oxygenation depends on alveolar ventilation, patients are often hypoxic*

* the hypoxia improves with supplemental oxygen

Clinical manifestations

• in patients with respiratory muscle weakness & obesity-hypoventilation syndrome first hypoventilate during REM sleep.

Laboratory

• arterial blood gas for pCO2

Diagnostic procedures

• pulmonary function testing
  • evaluation of maximum inspiratory pressures & expiratory pressures & changes in vital capacity with changes in position helpful to assess role of neuromuscular weakness
  • with neuromuscular weakness
    • DLCO is normal
    • > 20 decline in FVC in supine position vs upright position
    • maximal inspiratory pressure < -60 cm H20 or < 50% of predicted
    • maximal expiratory pressure < +60 cm H20 or < 50% of predicted
• polysomnography if nocturnal hypoventilation is suspected
  • daytime sleepiness, nocturnal awakenings, morning headaches

Management

• non-invasive positive-pressure ventilation is superior to high-flow nasal cannula in patients with moderate hypercapnic respiratory failure during COPD exacerbation

More general terms

• respiratory failure

More specific terms

• acute hypercapneic respiratory failure
• chronic hypercapneic respiratory failure