End-Tidal CO2 and Different Health Problems

- Updated on April 23, 2023

End-Tidal CO2 and Different Health Problems 1By Dr. Artour Rakhimov, Alternative Health Educator and Author

BPT (Buteyko Practitioner Training) Module

How Buteyko practitioners can measure changes in breathing of their students

End-Tidal CO2 and Different Health Problems 2

Minute ventilation, although a very important respiratory parameter, needs special equipment and does not always indicate hyperventilation and small aCO2. Inaccuracies occur in cases of small body weight (found, for example, in children), irregular or very shallow breathing found in some obese patients, and obstruction of airways leading to partial or total closure of some lung areas. This last phenomenon will be discussed in the next section.

As a result, many professional researchers, when investigating respiration, often measure etCO2 (end-tidal CO2) as a more accurate characteristic reflecting CO2 content of the lungs. A device called a “capnometer” can continually measure CO2 levels in the expired air. The level of CO2 gradually rises during exhalation showing an approximate equalization with the CO2 value in alveoli in the lungs (hence, the phrase “end-tidal”). The normal alveolar CO2 pressure is about 40 mm Hg pressure (Guyton, 1984; Ganong, 1995) or partial pressure of 5.3% of normal air at sea level. According to “Handbook on physiology” (Severinghaus JW, 1965), “A PCO2 below 35 mm Hg is indicative of alveolar hyperventilation” (p.1476). 35 mm Hg corresponds to 4.6% CO2 at sea level (see Appendix 2 to find the relationships between aCO2% and absolute aCO2 pressure at different altitudes).

All previously quoted studies (section 1.1) indicating hyperventilation should find abnormally low etCO2 for tested patients. Indeed, people who breathe more should generally show smaller CO2 concentrations in expired air. What also follows from many studies is that with the deterioration of health etCO2 tension gets even lower. The investigation of over 100 patients (Tanabe et al, 2001) with different degrees of chronic heart failure revealed that class I patients (light degree) had about 34.5 mm Hg etCO2 pressure, class II patients: 32.5 mm Hg, and class III patients: 30.8 mm Hg. Thus, the heart patients with the more serious heart problems had lower CO2 levels and, therefore, heavier breathing in terms of minute ventilation.

American scientists from the Brown Medical School in Providence recently published a study on End-tidal carbon dioxide that predicts the presence and severity of acidosis in children with diabetes (Fearon & Steele, 2002). They start this publication with, “Patients with diabetic ketoacidosis (DKA) hyperventilate, lowering their alveolar (PACO(2)) and arterial carbon dioxide (PaCO(2))”. Their conclusion was, “End-tidal CO(2) is linearly related to HCO(3) and is significantly lower in children with DKA” (Fearon & Steele, 2002).

Expired end-tidal CO2 values are considered by many emergency professionals as an accurate predictor (life/death) of cardiac arrest. For example, the authors of the article “End-tidal carbon dioxide during cardiopulmonary resuscitation in humans presenting mostly with asystole: a predictor of outcome” investigated 120 French patients during non-traumatic cardiac arrest. The researchers found that “end-tidal CO2 could provide a highly sensitive predictor of return of spontaneous circulation during cardiopulmonary resuscitation (MPR)” (p.791, Cantineau et al, 1996). More recently a large group of medical doctors from several American hospitals tested over 100 patients and wrote an article “End-tidal carbon dioxide measurements as a prognostic indicator of outcome in cardiac arrest” with the same conclusion (Ahrens et al, 2001). There are several other studies written by emergency professionals, with the same conclusions.

Therefore, emergency patients (with cardiac arrest) with the deepest and frequent breathing have the least chances of survival.

Rosen and his colleagues (1990) in the abstract of the article “Is chronic fatigue syndrome synonymous with effort syndrome?” wrote: “Chronic fatigue syndrome (CFS), including myalgic encephalomyelitis (ME) and postviral syndrome (PVS), is a term used today to describe a condition of incapacity for making and sustaining effort, associated with a wide range of symptoms. None of the reviews of CFS has provided a proper consideration of the effort syndrome caused by chronic habitual hyperventilation. In 100 consecutive patients, whose CFS had been attributed to ME or PVS, the time course of their illness and the respiratory psychophysiological studies were characteristic of chronic habitual hyperventilation in 93. It is suggested that the labels ‘CFS’, ‘ME’ or ‘PVS’ should be withheld until chronic habitual hyperventilation – for which conventional rehabilitation is available – has been definitively excluded.”

Paulley started his article “Hyperventilation” (Paulley, 1990), with “Physicians’ and specialists’ continued failure to recognize, diagnose and treat adequately the majority of hyperventilators is a disgrace. Hyperventilation Syndrome (H.V.S.), incorrectly labeled myalgic encephalomyelitis (M.E.), is the latest example of the profession’s incompetence.”

These doctors claim that chronic fatigue syndrome, myalgic encephalomyelitis, and postviral syndrome can be directly caused by over-breathing since the normalization of breathing results in the recovery of the patients with these health concerns.

Capnometers (devices to measure carbon dioxide levels in the expired air) have become especially popular among psychologists. For example, Fried and colleagues (1990) studied several groups of subjects with anxiety, panic phobia, depression, migraine, and idiopathic seizures. The abstract claims that “virtually all the non-control subjects were found to show moderate to severe hyperventilation and the accompanying EEG dysrhythmia” (p.67).

Abnormally low carbon dioxide values (etCO2) were found in all (over 60) patients with neurotic depression and non-retarded endogenous depression (Damas Mora et al, 1976).

Asmundson and Stein (1994) measured carbon dioxide concentrations in over 20 patients with panic disorder. Their average CO2 was also below the medical norm.

Therefore, various psychological problems are connected and can be the consequences of chronic over-breathing.

Extract from Dr. Artour Rakhimov's Amazon book "Normal Breathing: The Key to Vital Health", also available in PDF.