Hypobaric Test Research Articles

In-Vitro Performance of the Enlite Sensor in Various Glucose Concentrations during Hypobaric and Hyperbaric Conditions

There is a need for reliable methods of glucose measurement in different environmental conditions. The objective of this in vitro study was to evaluate the performance of the Enlite® Sensor when connected to either the iPro™ Continuous Glucose Monitor recording device or the Guardian® REAL-Time transmitting device, in hypobaric and hyperbaric conditions. Sixteen sensors connected to eight iPro devices and eight Guardian REAL-Time devices were immersed in three beakers containing separate glucose concentrations: 52, 88, and 207 mg/dl (2.9, 4.9, and 11.3 mmol/liter). Two different pressure tests were conducted: a hypobaric test, corresponding to maximum 18000 ft/5500 m height, and a hyperbaric test, corresponding to maximum 100 ft/30 m depth. The linearity of the sensor signals in the different conditions was evaluated. The sensors worked continuously, and the sensor signals were collected without interruption at all pressures tested. When comparing the input signals for glucose (ISIGs) and the different glucose concentrations during altered pressure, linearity (R(2)) of 0.98 was found. During the hypobaric test, significant differences (p < .005) were seen when comparing the ISIGs during varying pressure at two of the glucose concentrations (52 and 207 mg/dl), whereas no difference was seen at the 88 mg/dl glucose concentration. During the hyperbaric test, no differences were found. The Enlite Sensors connected to either the iPro or the Guardian REAL-Time device provided values continuously. In hyperbaric conditions, no significant differences were seen during changes in ambient pressure; however, during hypobaric conditions, the ISIG was significantly different in the low and high glucose concentrations.

Hematological alterations and response to acute hypobaric stress.

Exposure of rats to simulated altitude (15,000 ft) for 1 day and 3 and 9 wk produced progressive polycythemia, elevated 2,3-diphosphoglycerate levels and raised P50 values; the latter two parameters decreased toward control values after 9 wk. Carbon monoxide (38-43% HbCO) exposure produced polycythemia after 3- and 9-wk exposure, no change in 2,3-DPG and a fall in P50 value. Ten days' treatment with sodium cyanate produced a large decrease in 2,3-DPG and P50. Survival during 90 min of acute hypobaria (0.3 atm) under Nembutal anesthesia was highest with NaOCN (75%), intermediate with 3- and 9-wk exposure to altitude and CO (56-58%) lower in 1-day altitude exposure (44%) and lowest in controls (5%). Heart and ventilation rate was monitored during this hypobaric test and response patterns established for each exposure/treatment. In states of extreme oxygen deprivation the results suggest, in order of importance, the survival value of 1) increased oxygen-hemoglobin affinity, and 2) polycythemia.