From the Guidelines
Hypercarbia should be managed by targeting a SaO2 range of 88-92% in vulnerable patients, such as those with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) or obesity-hypoventilation syndrome (OHS), to avoid oxygen-induced hypercapnia. This approach is supported by the British Thoracic Society (BTS) guideline for oxygen use in adults in healthcare and emergency settings 1. Hypercarbia is a condition characterized by elevated levels of carbon dioxide (CO2) in the bloodstream, typically defined as a partial pressure of CO2 (PaCO2) greater than 45 mmHg. It occurs when the body cannot effectively eliminate CO2 through respiration, leading to respiratory acidosis. Common causes include respiratory depression from medications, chronic obstructive pulmonary disease (COPD), severe asthma, neuromuscular disorders affecting breathing, and sleep apnea.
Causes and Treatment
Treatment depends on the underlying cause but generally focuses on improving ventilation. For acute severe hypercarbia, supplemental oxygen and possibly mechanical ventilation may be required. In medication-induced cases, reversal agents like naloxone might be needed. For COPD exacerbations, bronchodilators such as albuterol and corticosteroids are often prescribed. Noninvasive positive pressure ventilation (NIPPV) with settings typically starting at IPAP 10-12 cmH2O and EPAP 4-5 cmH2O may be used for moderate to severe cases, as suggested by the BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults 1.
Management Considerations
It is essential to consider the potential for oxygen-induced hypercapnia in vulnerable patients and to use targeted lower concentration oxygen therapy to avoid this complication. The BTS guideline recommends aiming for a target range of 88-92% SaO2 in these patients 1. Additionally, the BTS/ICS guideline suggests that in acute respiratory distress syndrome (ARDS), a low tidal volume strategy improves survival, and in airflow obstruction, prolonging the expiratory time reduces dynamic hyperinflation (gas-trapping) 1.
Key Points
- Hypercarbia is a condition characterized by elevated levels of carbon dioxide (CO2) in the bloodstream.
- Treatment depends on the underlying cause but generally focuses on improving ventilation.
- Targeting a SaO2 range of 88-92% in vulnerable patients can help avoid oxygen-induced hypercapnia.
- Noninvasive positive pressure ventilation (NIPPV) may be used for moderate to severe cases.
- Low tidal volume strategy improves survival in ARDS, and prolonging the expiratory time reduces dynamic hyperinflation in airflow obstruction.
From the Research
Hypercarbia Overview
- Hypercarbia, also known as hypercapnia, is a condition characterized by an excess of carbon dioxide in the blood [(2,3,4)].
- It can occur in patients with chronic obstructive pulmonary disease (COPD) who receive oxygen therapy [(2,3,4)].
Causes of Hypercarbia
- The abolition of 'hypoxic drive' is one of the mechanisms leading to the development of oxygen-induced hypercapnia 4.
- Loss of hypoxic vasoconstriction and absorption atelectasis can also lead to an increase in dead-space ventilation and the Haldane effect, resulting in hypercarbia [(3,4)].
- Hypercarbia can also be caused by other factors such as morbid obesity, asthma, cystic fibrosis, chest wall skeletal deformities, bronchiectasis, chest wall deformities, or neuromuscular disorders 4.
Effects of Hypercarbia
- Hypercarbia can lead to a decrease in glottic closing force, making patients more susceptible to aspiration 5.
- It can also lead to changes in physiologic deadspace, resulting in hypercarbia 3.
- Hypercarbia can have significant clinical implications, including increased risk of respiratory tract infections and other life-threatening complications [(4,5)].
Management of Hypercarbia
- The international guideline recommends a target oxygen saturation of 88% to 92% in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and other chronic lung diseases at risk of hypercapnia 4.
- Oxygen should be administered only when oxygen saturation is below 88% 4.
- Other management strategies, such as high-flow oxygenation or extracorporeal carbon dioxide removal, may also be effective in improving clinical outcomes and functional recovery in patients with COPD 6.