Comparison of the Human Transcriptional Response to Three Hypoxic Environments

Hypoxia training is a standard facet of military aviator training, performed to familiarize airmen with the symptoms of hypoxia. The three most common devices used for this training are the hypobaric altitude chamber (AC) or the normobaric restricted oxygen breathing device (ROBD) and restricted oxygen breathing environment (ROBE). The AC creates hypoxic conditions by means of reduced atmospheric pressure. The ROBD and ROBE create normobaric hypoxic conditions by supplying a controlled reduced-oxygen gas mixture to trainees who don an aviation-style breathing mask or occupy a sealed chamber, respectively. In order to determine if differences in the transcriptional response to each of these training devices exist, blood RNA from ten volunteer subjects was analyzed by microarray, and resulting gene expression measures were screened for significant changes across timepoints within and across device runs. Few genes were significant in these comparisons, most significant differences between timepoints were in small nucleolar RNAs and non-coding RNAs, as well as one microRNA and transfer RNA. As unique genes were changed by each device, the transcriptional response to each device does differ slightly. However, the role of these transcriptional changes is unclear, as little information exists as to their function or role in the hypoxic response. As all of the examined devices induce hypoxic symptoms, and very little difference was observed in gene expression within devices, this limited study did not detect the presence of substantial differences between hypoxia training devices. Future studies utilizing more sensitive sequencing-based gene expression analysis techniques may improve detection of transcriptional differences induced by each device.