We appreciate the interest to our manuscript and the overall mode of intermittent exposure to hypoxia in the occupational settings at high altitude, such as mines (Vinnikov et al., 2016). Indeed, these findings may sound quite novel, given the conventional understanding of hypoxic exposure as a stimulant and trigger of sympathetic activity. In many studies of acute exposure, blood pressure (BP) elevation has been well documented and discussed elsewhere. In contrast, with the chronic intermittent pattern of exposure, other prospective studies also showed trends toward gradual BP reduction, such as in a 2.5-year prospective observation of Chilean miners (Richalet et al., 2002). We in fact confirmed their findings with almost similar altitude and exposure pattern. For sure, we do not stipulate to generalize our findings onto healthy alpinists or any other groups exposed in any otherwise modes, such as once-a-year sojourns. We believe that our findings should be treated with caution and in light of occupational health surveillance and screening of healthy miners. Therefore, we foresee mainly occupational application of our prospective observation data. In this context, fitness to work for healthy prospective employees with borderline hypertension is both ethical and juridical matters because a doctor in charge of fitness decision should have evidence from the scientific literature whether a patient with borderline or clinically meaningful hypertension is fit to work or not. Such decision is very often challenging. Moreover, with regard to respiratory fitness, it is hampered by no formal contraindications when clinical chronic obstructive pulmonary disease is yet absent, but the evidence from prospective observations is worrisome (Vinnikov et al., 2011). Our article along with other observations in Chilean miners (Richalet et al., 2002; Farías et al., 2006; Brito et al., 2007) aimed to arm an occupational doctor with some evidence.
As for the terminology, this indeed should be discussed. The term “chronic intermittent hypoxia” has been proposed by Richalet et al. (2002) with quite clear justification why this term is prudent in such setting. The major argument was the accessibility of work site with the corresponding hypoxia exposure in a relatively short period, using buses, helicopters, and other modes of rapid transportation. With such mode of exposure, normoxia at home shifts to almost instantly occurring hypobaric hypoxia at the mine. Neurohumoral mechanisms of acclimatization will differ from those in intermittent hypoxia during sleep, as will BP. However, we believe that the proposed term “chronic intermittent hypoxia” is quite relevant for long-lasting cycles of intermittent exposure with rapid transportation and should be reserved for the occupational context. We would like to invite the scientific community to join this discussion and propose better terminology to avoid any confusion in data interpretation.
