Erytropoietin and central venous pressure in high altitude shift workers

Resumen

It was the hypthesis that in shift workers with a history of intermittent hypoxic stress (working 10 days at > 3,600 m, then 4 days rest at sea-level) for > 5 years the initial erythropoietin (EPO) response, and the changes in central venous pressure (CVP) are different from Caucasian low-landers. Because the interstitial compartment belongs to the low pressure system, it was an additional aim of the study to quantify fluid distribution changes in the superficial tissues along the body axis during such an intermittent hypoxic stress. Therefore, an ultrasound device was used to measure the tissue thickness changes at head (front) and tibia in shift workers and Caucasian low-landers. In addition, blood samples were analysed for colloid osmotic pressure (COP) and albumin (ALB) concentrations to evaluate wheter fluid shifts from the intravascuiar to the extravascular compartment are probably due to changes in COP and ALB concentrations. We studied the kitchen personnel (N=11) of the goldmine La Coipa (3,600 m) and a group of Caucasian low-landers (N=5). Blood samples were taken and CVP and tissue thickness TT determined several times before, during, and after a typicai shift. At baseline data collection (BDC) prior to transition the shift workers had EPO concentrations of 5.2 + 2.4 mU-ml-1, which increased at altitude (P<0.01) and returned to BDC values on the recovery (day 16). The Caucasians showed the same time course. CVP values in the shift workers were generally higher than in the Caucasians. The tissue thickness at the front in shift workers increased significantly at altitude exposure (P < 0.05) and remained elevated in the recovery period altitude (P < 0.05) . The tissue thickness at the tibia showed no significant changes. Similar tissue thickness changes could be observed in the Caucasian low-landers. In conclusion, the hypothesis has to be refuted that the initial EPO response to a hypoxic stimulus is aitered in these shift workers. Higher hemoglobin concentrations and/or CVP values found in shift workers might be responsible for the rather low EPO concentrations observed in shift workers at BDC. Furthermore, shift workers and Caucasian low-landers showed measurable fluid accumulations in the superficial tissue of the upper part of the body after transition from sea-level to high altitude.