Ascent to altitude presents a significant challenge to the human body. Specifically, it is associated with an increased ventilation and pulmonary vasoconstriction. In healthy subjects these are related such that a high ventilatory drive is associated with blunted pulmonary vasoconstriction. Adults born prematurely and given supplemental oxygen at birth have a blunted ventilatory response to hypoxia. We hypothesized that the hypoxic ventilatory and pulmonary vasoconstrictor responses would be unrelated following perinatal supplemental oxygen exposure. To test our hypothesis, we used a well-established rat model of 80% O2 (80%) exposure for 14 days post-natally, with 21% O2 exposure as a control (21%). We assessed the ventilatory response to graded hypoxia using barometric plethysmography 6-9 months post hyperoxia exposure. The left and right ventricles were catheterized to evaluate the hemodynamic response to 10 minutes of 12% O2 (hypoxia). To our surprise we found that 80% animals did not demonstrate a depressed ventilatory response to hypoxia. However, these animals experienced increased right ventricular systolic pressure in response to 12% O2. An increase in cardiac output was the primary driving force behind the increase in right ventricular end systolic pressure, not an increase in vascular resistance. We found no relationship between the hypoxic ventilatory drive and right ventricular pressure. In 21% animals exposed to hypoxia, the increase in right ventricular pressure was driven primarily by vasoconstriction and, as previous studies have shown, there was a relationship between the ventilatory and pressure responses. These data suggest that neonatal supplemental oxygen alters the hemodynamic response to hypoxia, possibly through enhanced sympathetic drive. The relationship between ventilation and pulmonary pressure may not translate to individuals born prematurely.

Background Oxygen is one of the most commonly used drugs by anesthesiologists. The World Health Organization (WHO) gave recommendations regarding perioperative oxygen administration, but the practice of oxygen use in anesthesia, critical emergency, and intensive care medicine remains unclear. Methods We conducted an online survey among members of the European Society of Anaesthesiology and Intensive Care (ESAIC). The questionnaire consisted of 46 queries appraising the perioperative period, emergency medicine and in the intensive care, knowledge about current recommendations by the WHO, oxygen toxicity, and devices for supplemental oxygen therapy. Results Seven hundred ninety-eight ESAIC members (2.1% of all ESAIC members) completed the survey. Most respondents were board-certified and worked in hospitals with > 500 beds. The majority affirmed that they do not use specific protocols for oxygen administration. WHO recommendations are unknown to 42% of respondents, known but not followed by 14%, and known and followed by 24% of them. Respondents prefer inspiratory oxygen fraction (FiO2) ≥80% during induction and emergence from anesthesia, but intraoperatively < 60% for maintenance, and higher FiO2 in patients with diseased than non-diseased lungs. Postoperative oxygen therapy is prescribed more commonly according to peripheral oxygen saturation (SpO2), but shortage of devices still limits monitoring. When monitoring is used, SpO2 ≤ 95% is often targeted. In critical emergency medicine, oxygen is used frequently in patients aged ≥80 years, or presenting with respiratory distress, chronic obstructive pulmonary disease, myocardial infarction, and stroke. In the intensive care unit, oxygen is mostly targeted at 96%, especially in patients with pulmonary diseases. Conclusions The current practice of perioperative oxygen therapy among respondents does not follow WHO recommendations or current evidence, and access to postoperative monitoring devices impairs the individualization of oxygen therapy. Further research and additional teaching about use of oxygen are necessary.