Simulated airplane flight increases plasma lactate in fetal rabbits.

We studied the effect of 9 h of simulated airplane cabin conditions at cruising altitude (8,000 feet; inspired oxygen equivalent to 15% O2 at sea level) on fetal plasma lactate in near-term pregnant rabbits. Controls (n = 19) spent 9 h at sea level (21% O2). Study group I (n = 21) experienced airplane cabin conditions. Study group II (n = 17) was studied at 8,000 feet with the inspired O2 concentration normalized to sea level. Study group III (n = 19) remained at sea level breathing 15% O2. Before ending each exposure, fetal blood sampling for lactate was performed under ultrasound guidance. Maternal lactates were obtained before and after sampling fetuses. Wilcoxon signed rank test, analysis of variance, and Bonferroni's method were used as appropriate. P < 0.05 denoted statistical significance. Study group I (altitude/hypoxia) had higher fetal lactates than controls (sea level/normoxia) and study group II (altitude/normoxia). Fetal lactates in study group I (altitude/hypoxia) were higher than in study group III (sea level/hypoxia). Maternal lactates were lower after fetal sampling. Fetal lactic acidemia was observed after 9 h of airplane cabin conditions. This was attributed to the combined effect of the lowered oxygen concentration and the decrease in atmospheric pressure.

Effect of hyperbaric oxygen on the blood: cerebrospinal fluid transfer of tobramycin.

The blood:cerebrospinal fluid (CSF) transfer of the aminoglycoside antibiotic, tobramycin (TOB) was assessed in rabbits. The CSF:blood ratio of TOB, 90 min after a subcutaneous injection, was approximately 1:100 as measured by an agar disc diffusion bioassay. Hyperbaric oxygen therapy at a pressure of 3 ATA caused a slight, non-significant, increase in this ratio, while high dose carbon dioxide, a treatment known to damage the blood:brain barrier, more than doubled this ratio. Thus, hyperbaric oxygen has no significant effect on CSF concentration of TOB in rabbits with intact meninges.