From the Guidelines
To treat hypercapnia, non-invasive ventilation (NIV) with targeted oxygen therapy should be initiated if the patient is hypercapnic (PCO2 >6 kPa or 45 mm Hg) and acidotic (pH<7.35 or [H+]>45 nmol/L), as this approach has been shown to improve outcomes in patients with chronic obstructive pulmonary disease (COPD) 1. When managing hypercapnia, it is crucial to address the underlying cause while supporting respiratory function.
- For patients with COPD, careful monitoring for hypercapnic respiratory failure with respiratory acidosis is necessary, even if initial blood gases are satisfactory 1.
- Avoid excessive oxygen use, as it can increase the risk of respiratory acidosis in patients with hypercapnic respiratory failure 1.
- Targeted oxygen therapy should aim for an oxygen saturation of 94–98% unless there is a history of previous hypercapnic respiratory failure requiring NIV or intermittent positive pressure ventilation 1.
- NIV has been shown to be effective in reducing PaCO2 levels in patients with hypercapnic COPD, with high-intensity NIV being a promising approach 1.
- In addition to NIV, treating underlying conditions such as bronchospasm with bronchodilators like albuterol, and managing conditions like COPD with pulmonary rehabilitation and smoking cessation, are essential for improving outcomes in patients with hypercapnia.
- It is also important to avoid sedatives when possible, as they can depress respiratory drive and worsen hypercapnia.
- Regular monitoring of blood gases is necessary to adjust therapy and prevent complications, with rechecks every 30–60 min or if there is evidence of clinical deterioration 1.
From the FDA Drug Label
Acetazolamide is a potent carbonic anhydrase inhibitor, effective in the control of fluid secretion Acetazolamide is an enzyme inhibitor that acts specifically on carbonic anhydrase, the enzyme that catalyzes the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid
The treatment of hypercapnia (elevated carbon dioxide levels) with acetazolamide may be considered, as it inhibits carbonic anhydrase, the enzyme involved in the reversible reaction of carbon dioxide hydration. However, the label does not directly address the treatment of hypercapnia.
- Key mechanism: inhibition of carbonic anhydrase
- Effect on carbon dioxide: hydration of carbon dioxide is affected by the inhibition of carbonic anhydrase 2
From the Research
Treatment Options for Hypercapnia
- Non-invasive ventilation through a facemask is the cornerstone first-line strategy to support hypercapnic patients with acidemia, as recommended by current guidelines 3
- High-flow nasal oxygen has been proposed as a respiratory support strategy in patients with hypercapnic respiratory failure, both as an alternative to and in combination with noninvasive ventilation 3
- Conventional oxygen therapy could be delivered via nasal prongs, face mask, venturi mask, or non-rebreather mask, but high flow nasal cannula (HFNC) produces a higher flow of FiO2, creating a positive pressure on the higher respiratory tract and improving oxygenation and reducing the total work of breathing 4
- Controlled oxygen therapy can be used to prevent carbon dioxide retention during exacerbations of chronic obstructive pulmonary disease (COPD), with a target oxygen saturation of 88% to 92% 5, 6
Administration of Oxygen Therapy
- Oxygen should be administered only when oxygen saturation is below 88% 5
- Optimal settings of high-flow nasal oxygen in hypercapnic patients include the use of a smaller-size cannula, flows ranging between 30 and 40 L/min, and FiO2 adjusted to obtain SpO2 between 88% and 92% 3
- Careful titration of oxygen therapy is needed in COPD patients, particularly those with baseline hypercapnia, to prevent worsening hypercapnia when flow rate is unchanged 7