Volunteers who were able to complete the test had increased brain saturation and in a real-world situation, would have been the ones likely to have developed three H syndrome: their bodies cooled down but the snow still provided sufficient oxygen and carbon dioxide removal. In contrast, the subjects who could not complete the test showed declining brain saturation, possibly due to there not being enough oxygen in the snow or adequate carbon dioxide removal putting the subjects at risk of developing a dangerous condition which, if prolonged, would result in brain damage (as well as cardiovascular damage owing to a disruption of the protective cooling process and even cardiac arrest).
The experiment not only demonstrated, for the first time, the link between oxygenation of the human brain, air in the snow and the onset of three H syndrome but also how, up to a certain threshold, reduced availability of oxygen does not always lead to a reduction in oxygen in the brain. The brain has self-regulating and compensating mechanisms which, under certain conditions and periods of time, guarantee an adequate supply of oxygen.
"By using NIRS in this study, we have confirmed both the importance of adequate cerebral oxygenation for survival without consequences, as well as the characteristics of the snow in an avalanche burial. With low and medium density snow, the chances of the victim avoiding a state of asphyxiation are greater," explains Giacomo Strapazzon, lead author of the article and deputy director of the Eurac Research Institute of Mountain Emergency Medicine.
"As is often the case with basic research, the results obtained are not reflected in today’s clinical practice. If we continue in this direction, we could evaluate how NIRS might improve the pre-hospitalisation triage and treatment of avalanche victims to understand whether, at the time of extraction, patients are already suffering brain damage," Strapazzon concludes.