From the Guidelines
A pCO2 of 10.8 mmHg is critically low and indicates severe respiratory alkalosis, which requires immediate medical attention. This patient needs prompt evaluation for the underlying cause, which may include hyperventilation, severe anxiety, sepsis, liver failure, pulmonary embolism, or central nervous system disorders. According to the BTS guideline for oxygen use in adults in healthcare and emergency settings 1, carbon dioxide levels in the blood are controlled by chemical sensors, and the normal range is 4.6–6.1 kPa or 34–46 mm Hg.
- Key points to consider in management include:
- Treating the underlying cause while supporting the patient's respiratory status
- Administering oxygen therapy if hypoxemia is present
- Using IV fluids if the patient is dehydrated
- Continuous monitoring of vital signs and arterial blood gases
- It is essential to note that this extreme respiratory alkalosis can cause serious complications, including seizures, arrhythmias, and tetany due to decreased ionized calcium, as the normal pCO2 range is 35-45 mmHg, and this value represents a severe deviation that can significantly impair oxygen delivery to tissues by shifting the oxyhemoglobin dissociation curve 1.
From the Research
pCO2 Levels
- A pCO2 level of 10.8 is considered low, as normal pCO2 levels typically range from 35 to 45 mmHg 2.
Relationship to Anxiety Disorders
- Low baseline pCO2 has been associated with higher anxiety symptoms and lower quality of life in individuals with anxiety disorders 2.
Treatment Implications
- Benzodiazepines are not recommended as a first-line treatment for dyspnea in advanced illnesses, due to potential adverse effects such as delirium and drowsiness 3.
- However, benzodiazepines may be considered in highly selected patients with severe anxiety associated with dyspnea, or as an adjunctive treatment in patients with severe dyspnea despite opioids 3.
COPD Considerations
- Ventilation-perfusion inequality is a common cause of impaired gas exchange in patients with lung disease, including COPD, and can lead to hypercapnia (elevated pCO2) 4.
- Increasing ventilation can help return arterial pCO2 to normal in patients with COPD, but may not improve arterial oxygen levels due to the different shapes of the oxygen and carbon dioxide dissociation curves 4.