Nocturnal periodic breathing at altitude: the consequences

Humans sleeping at high altitude often experience so called periodic breathing, where complete stops of breathing alternate with phases of highly increased breathing. While at normal altitude, such periodic breathing has a variety of adverse health effects, its consequences at high altitude are poorly understood. Our study aims to investigate whether nocturnal periodic breathing at high altitude contributes to four different phenomena that are commonly observed at high altitude. These phenomena are: 1. Activation of the portion of our nervous system that mediates stress responses 2. Acute mountain sickness, a condition characterized by headache and nausea 3. Deterioration of sleep quality 4. Increased breathing during wakefulness To determine the contribution of periodic breathing to these phenomena, we will let 16 test persons spend two three-day sojourns in the terraXcube, the climate chamber of EURAC Research in Bolzano (https:/erraxcube.eurac.edu). Throughout both sojourns, the barometric pressure in the terraXcube and hence the oxygen content will be reduced to the equivalent of 4,000 m altitude. During one of the two sojourns we will throughout the nights administer a small amount of carbon dioxide to the breathing air of the test persons. This will stimulate their breathing and thereby prevent periodic breathing. During the other sojourn the breathing of the test persons will not be manipulated so that periodic breathing will occur. The test persons will not know, during which of the two sojourns the carbon dioxide administration takes places. At the end of the sojourns we will measure the activation of the above-mentioned portion of the nervous system by introducing a very thin needle into a nerve and counting the electric impulses. Throughout both sojourns we will furthermore assess symptoms of acute mountain sickness and determine how much breathing is increased. Furthermore, we will evaluate sleep quality by measuring brain and muscle activity throughout the nights. If the phenomena outlined above are indeed related to the periodic breathing at high altitude, we expect them to be absent or at least less pronounced after the sojourn where breathing is simulated by carbon dioxide than after the sojourn where breathing is not manipulated.