Effects of hypoxia on blood pressure regulation: interval hypoxic training as compared to obstructive sleep apnea – the other side of the coin?

Abstract

Introduction In this issue of the Journal of Hypertension, an article by Haider et al. [1] provides evidence on the possibility to apply a respiratory training technique, based on intermittent respiration of a gas mixture exposing patients to normobaric hypoxia, in the nonpharmacological treatment of patients with chronic obstructive pulmonary disease (COPD). These patients are characterized by a low ventilatory drive to carbon dioxide and thus are at increased risk of developing hypercapnia, hypoxemia at night and elevated pulmonary artery pressure. An intervention aimed at improving their cardiorespiratory regulation would thus be welcome. The approach proposed by the authors, termed interval hypoxic training (IHT), was originally developed in the former Soviet Union in the 1990s, after which time it has been largely overlooked until recently. According to the hypothesis made by Haider et al., IHT may represent an alternative or supplementary form of rehabilitation, besides the traditional physical training, for COPD patients. In patients with chronic pulmonary disease, in whom the same investigators demonstrated the possibility to obtain favorable results with regular performance of a slow breathing exercise [2], the conventional training of respiratory muscles has worthy but limited results [1]. According to the data obtained by Haider et al., intermittent breathing of hypoxic gas mixtures could offer a better outcome in terms of cardiovascular regulation. Hereafter, a brief description of this technique and of the putative mechanisms involved in its effects is provided for the nonfamiliar reader.