Elsevier

Medical Hypotheses

Volume 110, January 2018, Pages 101-104
Medical Hypotheses

Carbon dioxide therapy in hypocapnic respiratory failure

https://doi.org/10.1016/j.mehy.2017.11.010Get rights and content

Abstract

Oxygen therapy, usually administered by a facemask or nasal cannulae, is the current default treatment of respiratory failure. Since respiration entails intake of oxygen and release of carbon dioxide from tissues as waste product, the notion of administering carbon dioxide in respiratory failure appears counter-intuitive. However, carbon dioxide stimulates the chemosensitive area of the medulla, known as the central respiratory chemoreceptor, which activates the respiratory groups of neurones in the brainstem and stimulates inspiration thereby initiating oxygen intake during normal breathing. This vital initiation of normal breathing is via a reduction in the pH of the cerebrospinal fluid and the medullary interstitial fluid. We hypothesise that in cases of type I respiratory failure in which the PaCO2 is low, administration of carbon dioxide by inhalation would stimulate the respiratory groups of brainstem neurones and facilitate breathing, which would be of therapeutic value. Preliminary clinical evidence in favour of this hypothesis is presented and we recommend that a formal randomised study be carried out.

Section snippets

Introduction and background

Human respiration entails intake of oxygen and release of carbon dioxide [1]. We propose here to divide this process into three phases carried out by different sets of effectors organs. Phase 1 is the acquisition of oxygen from the atmosphere by the cooperation of the heart and the lungs. Phase 2 is the transportation and delivery of respiratory gases for consumption or excretion by the cooperation of the heart and the blood vessels. Phase 3 is the consumption of oxygen and production of carbon

The hypothesis

We hypothesise that carbon dioxide is a major regulatory molecule in all three above-mentioned phases of respiration; here we shall only consider its role in phase 1 respiration. Since carbon dioxide (via a lower pH) stimulates the medullary chemosensitive areas known as central respiratory chemoreceptors, we hypothesise that in cases of type I respiratory failure in which the PaCO2 is low, administration of carbon dioxide by inhalation would stimulate the respiratory groups of neurones in the

Evaluation of the hypothesis and a test of concept

Therapeutic value of inhalation of carbogen (consisting of 5% carbon dioxide and 95% oxygen) has been demonstrated in patients with Rett syndrome with the clinical cardiorespiratory phenotype of forceful breathers. They had very low tissue pCO2 measured by transcutaneous methods using the TCM3 (Radiometer, Copenhagen, Denmark). The transcutaneous pCO2 was used as a surrogate of PaCO2. These patients had severe respiratory alkalosis and low tissue pO2 owing to the subsequent prolong apnoea

Discussion

The notion of administering carbon dioxide in respiratory failure appears counter-intuitive. However, respiratory failure has a complex nature and the arterial oxygen level is not the only index of respiratory failure. As the preliminary clinical data mentioned above have shown, carbon dioxide therapy can be of value. Carbon dioxide is highly important in the central stimulation of breathing. In particular, oxygen administration is not the only means of treating respiratory failure. Some

Conflicts of interest

None.

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