[Characterisation of hypobaric hypoxia at 2240 metres above sea level]

Hypobaric hypoxia is little known in healthy subjects at 2240 meters above sea level.

To characterize hypobaric hypoxia in healthy subjects at 2240 meters above sea level.

Healthy subjects residing in Mexico City were studied using an analytical cross-sectional design. Their demographic and oxygenation variables were analyzed by gender using the t test for independent variables and p < 0.05. Oxygenation indices were characterized using Pearson's correlation coefficient, intraclass correlation coefficient, and coefficient of determination.

A total of 244 healthy subjects residing in Mexico City, aged 49 ± 9, 122 (50%) males, were studied; body mass index in men: 22.92 ± 1.63 versus 22.87 ± 1.43 in women, p = 0.792. Total PaO2 was 69.88 ± 4.46; total SpO2 was 93.93 ± 1.90; PaO2/FiO2 ratio was 333 ± 21 and adjusted for barometric pressure was 256 ± 16; SpOFI/FiO2 was 447 ± 9 and adjusted for barometric pressure was 344 ± 7. The PaO2/FiO2 - SpOFI/FiO2 correlations were r = 0.631, p = 0.0001, and adjusted r = 0.629, p = 0.0001, concordance by intraclass correlation coefficient of 0.624 (substantial) and an adjusted of 0.543 (moderate). The coefficient of determination 39.8%, adjusted for barometric pressure 39.5%.

At 2,240 meters above sea level, oxygenation variables indicate the presence of hypobaric hypoxia. The oxygenation indices correlate with moderate to substantial concordance.