Hypocapnia or Hypocapnea: Symptoms, Treatment and Diagnosis

Definition: Also called Hypocapnea.

It is defined as the lack or absence of carbon dioxide in the blood of the arteries. This is an important respiratory symptom that must be taken into consideration.

Medical sources have mostly defined hypocapnia as less than 35 mm Hg for the partial tension of CO2 in the blood of the arteries. On the other hand, the arterial CO2 value in the case of normal breathing in the resting state is 40 mm Hg (around 5.3% partial tension of CO2).

Abnormal decrease in blood pressure of carbon dioxide.

Hypocapnia is the result of over-breathing behavior, the lack of concordance between the respiratory rate and the depth of it.

Its consequence is a higher level of pH, or respiratory alkalosis, which can have profound immediate and long-term effects that trigger, exacerbate and / or cause a wide variety of emotional, perceptual, cognitive, attention, behavioral and physical deficits that can affect seriously the health and performance of those who suffer it.

Although the fundamental importance of CO2 in the regulation of body chemistry, pH and electrolyte balance, is common knowledge for any pulmonary physiologist, it remains virtually unknown by most health professionals, health educators, trainers of breathing and laity.

Hypocapnia can be the result of nervous, cardiovascular (eg, low blood pressure), respiratory (asthma), and metabolic (eg, diabetes) problems, including challenges such as drugs, hormonal changes (eg, during pregnancy). pregnancy), altitude, heat, lung irritants, severe exercise and others.

In many of these cases, hypocapnia plays an adaptive role, where it serves to compensate for pH dysregulation, as in cases of lactic acidosis during severe exercise and ketoacidosis in diabetes.

The so-called alveolar hypocapnia represents the low levels of CO2 in the alveoli of the lungs. In its severe form it usually leads to hypocapnia of the arteries, causing respiratory alkalosis.

Patients with pulmonary conditions may suffer from hypercapnia in the arteries (elevated CO2) due to hypocapnia in the pulmonary alveoli, since alveolar hypocapnia immediately causes bronchospasm.

Hypocapnia in the alveoli is quite common in a variety of chronic diseases. These patients who mostly suffer from heart disease, diabetes, cancer, etc. they also have arterial hypocapnia

It is caused by chronic hyperventilation (or an automatic deep breathing pattern) that leads to alveolar hypocapnia (total absence of CO2), and in case there is not a good and correct ventilation-perfusion, to the arterial deficiency of dioxide. carbon.

Imperceptible results in normal breathing, as it is light and soft (10 to 12 breaths per minute, 500 ml for the tidal volume and 6 L / min for minimum ventilation at rest in the case of a 70 kg person).

On the other hand, hypocapnic patients and even most healthy people breathe more than 10 l / min with more than 18 breaths / min of respiratory frequency.

Among the factors that cause hyperventilation are physical exercise through mouth breathing, meals (overeating), anxiety, stress, attempts to breathe deeply, deep breathing exercises (except Pranayama) in a horizontal position, bad position and many other factors.

Respiratory symptoms

People with mouth breathing since the hypocapnia is based on chronic hyperventilation, the symptoms are the same as those of hyperventilation. They are very broad, from chronic cough, nasal congestion to cough, constipation, and muscle cramps.

Other common symptoms of hypocapnia are bronchospasm, cold extremities, mouth breathing, exacerbations of asthma, angina pain, just to mention a few.

The pathological consequence is the reduction of oxygen levels in the cells (tissue hypoxia), this causes chronic diseases.

Severe hypocapnia: the most common factor of mortality in severely ill patients.

The terminally ill die in situations of severe hypocapnia due to rapid and heavy breathing. Patients with terminal cancer, HIV, cystic fibrosis and other conditions have breaths of up to 30-40 times per minute or more.

Respiratory alkalosis, the result of intense respiration in those who suffer from it, is the acid-base anomaly frequently observed in critically ill patients. It is frequent for those with large diseases, among which we have diabetes, AIDS, asthma, COPD, cardiovascular diseases, HIV, cancer, to name a few.

Treatment of hypocapnia

Since hypocapnia is based on excessive breathing, the procedure that really works with hypocapnia is focused on the treatment of the cause: chronic hyperventilation.

In this way, the procedure to be followed in cases of hypocapnia turns out to be the same as the procedure followed for hyperventilation.

Based on impressive clinical evidence (measurements of carbon dioxide in sick and healthy people), the Soviet physiologist Dr. KP Buteyko accompanied by some 150 doctors (believers of Buteyko’s breathing) suggested a different conceptualization for hypocapnia.

The doctors tested half a million individuals and found that good health; much energy, physical exercise, consuming unprocessed foods, naturally short sleep of 4 to 5 hours and other positive results are possible when people have even more CO2 in the pulmonary alveoli and blood from the arteries.


A physician will typically begin with a physical examination to determine the cause of the hypocapnia. He or she can ask a series of questions regarding the type of symptoms, characteristics in the hypocapnia, medications taken, medical conditions, feelings of anxiety or stress and other questions that can help determine the cause of the condition.

The following tests may also help diagnose episodes of hypocapnia:

  1. Arterial blood samples.
  2. Other blood tests
  3. X-rays of the thorax.
  4. Ventilation / perfusion scans.
  5. Computed tomography of the thorax.
  6. ECG (electrocardiograma).

Hypocapnia is more often the result of an exaggerated learning behavior, behavior dictated by the biological principles of learning, which include motivation, emotion, perception, memory and attention.

Behavioral hypocapnia is hypocapnia as a consequence of the behaviors learned. It points to the powerful role of respiration in the self-regulation of health and performance, where its effects are often identified as “inexplicable”, or simply not fully recognized.