Refractory hypercapnia

Specialty: Respiratory.

• persistent carbon dioxide retention
• refractory respiratory acidosis

Why it occurs

• Reacerbated chronic obstructive pulmonary disease (COPD) with extreme fatigue of the respiratory muscles and marked increase in alveolar dead space
• Obesity-hypoventilation syndrome (Pickwick syndrome, where the mechanical load imposed by abdominal and thoracic fat depresses the respiratory center and reduces tidal volume)
• Severe scoliosis or kyphoscoliosis with extreme restriction of the rib cage (leading to ineffective alveolar ventilation and long-term CO2 retention)
• Chronic overdose of benzodiazepines, barbiturates or persistent alcohol consumption in patients with previous respiratory pathology
• Advanced neuromuscular diseases (myasthenia gravis, Duchenne muscular dystrophy or ALS with involvement of the intercostal muscles and diaphragm).

Initial workup

Serial analytical arterial blood gases; Volumetric capnography or transcutaneous CO2 monitoring; Complete respiratory function tests with determination of maximum inspiratory and expiratory pressures (MIP and MEP); Computed tomography (CT) of the chest; Magnetic resonance imaging (MRI) of the brainstem if a pure central cause is suspected.

Standard management

• There are no effective direct respiratory drugs to eliminate CO2; The mainstay of treatment is non-invasive mechanical ventilation (BiPAP) with elevated inspiratory pressure parameters (IPAP) to optimize minute volume.
• Bronchodilators such as Salbutamol and Nebulized Ipratropium Bromide to reduce airway resistance
• Acetazolamide (carbonic anhydrase inhibitor diuretic, administered at doses of 250 mg orally or intravenously every 12-24 hours exceptionally to induce compensatory metabolic acidosis that stimulates the respiratory center, monitoring the hydroelectrolyte balance).