The ‘normobaric oxygen paradox’: a simple way to induce endogenous erythropoietin production and concomitantly raise hemoglobin levels in anemic patients.

Background: A novel approach to increasing erythropoietin (EPO) using oxygen (O2) (the 'normobaric oxygen paradox') has been reported in healthy volunteers. We investigated whether the EPO increase is sufficient to induce erythropoiesis by comparing two protocols of O2 administration. Methods: We compared the effect of daily versus alternate days 100% O2, breathed for 30 minutes, on haemoglobin concentrations during a 12-day period. Nine subjects underwent the two protocols six weeks apart.

The purpose of the study was to analyze the ultrasound lung comets (ULCs) variation, which are a sign of extra-vascular lung water. Forty-two healthy individuals performed breath-hold diving in different conditions: dynamic surface apnea; deep variable-weight apnea and shallow, face immersed without effort (static maximal and non-maximal). The number of ULCs was evaluated by means of an ultrasound scan of the chest, before and after breath-hold diving sessions. The ULC score increased significantly from baseline after dynamic surface apnea (p = 0.0068), after deep breath-hold sessions (p = 0.0018), and after static maximal apnea (p = 0.031). There was no statistically significant difference between the average increase of ULC scores after dynamic surface apnea and deep breath-hold diving. We, therefore, postulate that extravascular lung water accumulation may be due to other factors than (deep) immersion alone, because it occurs during dynamic surface apnea as well. Three mechanisms may be responsible for this. First, the immersion-induced hydrostatic pressure gradient applied on the body causes a shift of peripheral venous blood towards the thorax. Second, the blood pooling effect found during the diving response Redistributes blood to the pulmonary vascular bed. Third, it is possible that the intense involuntary diaphragmatic contractions occurring during the "struggle phase" of the breath-hold can also produce a blood shift from the pulmonary capillaries to the pulmonary alveoli. A combination of these factors may explain the observed increase in ULC scores in deep, shallow maximal and shallow dynamic apneas, whereas shallow non-maximal apneas seem to be not "ULC provoking".

PURPOSE: A reduction in ambient pressure or decompression from scuba diving can result in ultrasound-detectable venous gas emboli (VGE). These environmental exposures carry a risk of decompression sickness (DCS) which is mitigated by adherence to decompression schedules; however, bubbles are routinely observed for dives well within these limits and significant inter-personal variability in DCS risk exists. Here, we assess the variability and evolution of VGE for 2 h post-dive using echocardiography, following a standardized pool dive in calm warm conditions.