What are the causes of hypocapnia (low carbon dioxide levels)?

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Last updated: April 1, 2025 • View editorial policy

From the Guidelines

Low CO2 levels in the blood, also known as hypocapnia, can be addressed by identifying and treating the underlying cause, with treatment depending on the cause, such as breathing techniques for anxiety-related hyperventilation or electrolyte supplements for metabolic causes, as stated in the BTS guideline for oxygen use in adults in healthcare and emergency settings 1.

Causes of Low CO2 Levels

  • Hyperventilation, which can occur during anxiety attacks or physiological hyperventilation, as mentioned in the BTS guideline 1
  • Anxiety, high altitude exposure, severe infections, liver disease, or certain medications ### Treatment of Low CO2 Levels
  • Breathing techniques, such as breathing into a paper bag (not plastic) for a few minutes, can help restore CO2 levels in cases of anxiety-related hyperventilation
  • Electrolyte supplements, particularly bicarbonate, or adjustments to medications may be recommended by a doctor for metabolic causes
  • Staying hydrated and avoiding excessive caffeine or alcohol can support normal CO2 regulation ### Importance of Normal CO2 Levels
  • Carbon dioxide plays a crucial role in maintaining blood pH balance, and low CO2 levels can lead to respiratory alkalosis, affecting oxygen delivery to tissues and disrupting normal cellular function, as explained in the carbon dioxide physiology section of the BTS guideline 2
  • If symptoms like dizziness, confusion, numbness, or rapid breathing occur, seek immediate medical attention ### Prevention of Complications
  • Identifying and treating the underlying cause of low CO2 levels can help prevent complications such as respiratory alkalosis and oxygen delivery disruptions
  • Targeted lower concentration oxygen therapy may be necessary for vulnerable patients, such as those with AECOPD or OHS, to avoid oxygen-induced hypercapnia, as discussed in the BTS guideline 2

From the Research

Low CO2 Levels and Their Implications

  • Low CO2 levels, also known as hypocapnia, can be a key mechanism in the production and maintenance of panic disorder, as suggested by studies such as 3 and 4.
  • Hypocapnia can be caused by hyperventilation, which is a common symptom of panic disorder, and can lead to respiratory alkalosis, as described in 5.
  • The relationship between low CO2 levels and panic disorder is complex, and studies such as 6 and 7 have investigated the use of breathing training and voluntary hyperventilation in the treatment of panic disorder.
  • Breathing training therapies, such as those described in 3 and 7, have been shown to be effective in reducing panic symptoms and improving respiratory function in patients with panic disorder.
  • The use of capnometry feedback-assisted breathing training, as described in 7, can help patients with panic disorder to reduce hyperventilation and make their breathing more regular, leading to marked clinical improvement.

Physiological Markers for Anxiety

  • Physiological markers, such as hypocapnia and autonomic activation, can be used to diagnose and treat anxiety disorders, including panic disorder, as discussed in 7.
  • The measurement of physiological markers, such as CO2 levels and respiratory rate, can provide valuable information about the physiological mechanisms underlying anxiety disorders.
  • Studies such as 4 and 7 have investigated the role of hypocapnia and hyperventilation in the pathomechanism of panic disorder, and have suggested that these factors can play a key role in the development and maintenance of panic symptoms.

Treatment Implications

  • The treatment of panic disorder should address long-term regulation of the respiratory pattern and elimination of metabolic acidosis, as suggested by 4.
  • Breathing training therapies, such as those described in 3 and 7, can be an effective treatment for panic disorder, and can help patients to reduce hyperventilation and improve their respiratory function.
  • The use of voluntary hyperventilation and capnometry feedback-assisted breathing training can be a useful therapeutic approach for patients with panic disorder, as described in 6 and 7.

References

Research

The role of hyperventilation: hypocapnia in the pathomechanism of panic disorder.

Revista brasileira de psiquiatria (Sao Paulo, Brazil : 1999), 2007

Research

A Quick Reference on Respiratory Alkalosis.

The Veterinary clinics of North America. Small animal practice, 2017

Research

Physiological markers for anxiety: panic disorder and phobias.

International journal of psychophysiology : official journal of the International Organization of Psychophysiology, 2005

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