Since very low birth weight preterm newborns are prone to oxygen toxicity and have red blood cells that have a high oxygen affinity, the knowledge of the P90 (the Pao2 required for 90% saturation of hemoglobin) could result in a more optimal oxygenation. This information could diminish the incidence of bronchopulmonary dysplasia and retrolental fibroplasia. To determine P90 and P50 (the Pao2 required for 50% saturation of hemoglobin), cord blood was obtained from 10 preterm newborns who were of less than 30 weeks' gestation (26.4 ± 1.4 [SD] weeks) weighing less than 1000 g (816 ± 119 g). The P50 and P90 were determined by gas mixing tonometry and expressed in millimeters of mercury at a temperature of 37°C, a pH of 7.40, and Pco2 of 40 mm Hg. The tonometer permitted an equilibration and sampling of successive aliquots of blood at different oxygen tensions. Measurement of oxygen saturation, pH, and Pao2 provided the information for plotting the oxygen dissociation curve, the P50 and P90. There were at least six experimental points for each oxygen dissociation curve. The results showed that the mean P50 was 18.3 ± 1.9 mm Hg (2.5 ± 0.3 kPa) and the P90 was 40.8 ± 3.6 mm Hg (5.4 ± 0.5 kPa). This study demonstrates the fetal nature of the oxygen dissociation curve of very low birth weight newborns; but most importantly it also shows that when treating very low birth weight newborns with oxygen, a Pao2 of 41 mm Hg (5.5 kPa) is enough to saturate 90% of the hemoglobin at a physiological pH. This information could be of clinical importance to minimize oxygen toxicity.
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机译：由于出生体重非常低的早产儿容易产生氧气中毒，并且红细胞具有很高的氧气亲和力，因此了解P90（血红蛋白90％饱和所需的Pao2）可能会导致更理想的充氧。该信息可以减少支气管肺发育不良和后凸性纤维化的发生率。为了确定P90和P50（血红蛋白50％饱和所需的Pao2），从10胎龄小于30周（26.4±1.4 [SD]周）的早产新生儿中获取脐血，体重不足1000 g（816 ±119克）。通过气体混合眼压测定法确定P50和P90，并在37°C，pH 7.40和40mm Hg的Pco2下以毫米汞柱表示。眼压计允许在不同的氧气张力下对连续等分的血液进行平衡和采样。氧饱和度，pH和Pao2的测量提供了绘制氧解离曲线P50和P90的信息。每个氧解离曲线至少有六个实验点。结果表明，平均P50为18.3±1.9 mm Hg（2.5±0.3 kPa），P90为40.8±3.6 mm Hg（5.4±0.5 kPa）。这项研究证明了极低出生体重新生儿的氧解离曲线的胎儿特征。但最重要的是，它还表明，当用氧气治疗出生体重很轻的新生儿时，41 mm Hg（5.5 kPa）的Pao2足以在生理pH值下饱和90％的血红蛋白。该信息可能对降低氧气毒性具有临床重要性。
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