新生儿首次呼吸前后脐带动静脉血液氧和二氧化碳变化探索呼吸调控机制的初步报告I—血液氧和二氧化碳分压脐带动静脉差值的组间分析*

目的: 胎儿没有实际上的呼吸,新生儿出生后才开始呼吸,我们假设人的第一次呼吸主要是由于低氧而触发。本研究对流经主动脉体外周化学感受器后的脐带动脉血液氧分压（PuaO₂）变化规律和下限进行分析以探讨新生儿自主呼吸产生机制。方法: 选择签署知情同意书的正常分娩产妇数十例,仅14例新生儿在自主呼吸开始前成功完成脐带动脉或静脉置管。分别进行逐搏取血及顺序血气分析,计算血气指标的平均值、最高值和最低值,统计比较脐带动静脉的异同。结果: 在14例新生儿自主呼吸开始前完成采集脐带动脉（Pua）样本9例,脐带静脉（Puv）样本8例。就PO₂而言,所有9例PuaO₂随时间（心跳次数）呈逐渐降低倾向,直至在自主呼吸产生大约8~10次心跳后Pua挛缩、基本上无法取得足够的血样。PuaO₂平均值是（25.94±6.79,18.04~37.51）mmHg,最高值是（29.11±6.46,23.00~45.90）mmHg,最低值是（21.34±5.54,14.00~33.60）mmHg;但PuaCO₂变化趋势和规律则不够稳定,PuaCO₂平均值是（47.26 ±7.71） mmHg。PuvO₂随时间（心跳次数）虽也呈逐渐降低趋势,但多数还呈现随母亲呼吸节律的规律性交替升降的倾向,特别是母亲吸氧时。所有8例PuvO₂平均值是（53.35±21.35,32.56~100.73）mmHg,最高值是（90.38±48.44,43.40~153.00）mmHg,最低值是（36.96±14.90,24.80~73.80）mmHg;PuvCO₂平均值是（41.04±6.44)mmHg。虽然有着较大的个体差异,但 PuvO₂平均值、最高值和最低值均显著较PuaO₂高（P<0.05）;PuvCO₂虽略低于PuaCO₂,但无显著差异（P>0.05）。结论: 胎儿娩出为新生儿后自主呼吸前PuaO₂随时间（心跳次数）逐渐降低,在达到触发呼吸的阈值时诱发第一次吸气,从而开始自主呼吸。

Preliminary report on partial pressure changes of oxygen and carbon dioxide in umbilical artery and vein before and after the first breath in Chinese neonates I—The group difference of partial pressure of oxygen and carbon dioxide between umbilical artery and vein in newborns

Objective: The fetus has no actual respiration, and the newborn begins to breathe after birth. We assume that the first breath dominantly generated by hypoxia. In this study, the changes and lowest limit of blood oxygen partial pressureof umbilical artery (PuaO₂) after chemoreceptor were analyzed to explore the mechanism of neonatal spontaneous breathing. Methods: With signed consent form by all fetal parents before birth, 14 newborns successfully completed the umbilical artery or vein catheterization and drawn blood according to the heartbeat. All blood samples analyzed by blood gas analyzer,calculated and analyzed the similarities and differences between umbilical vein(Puv) and umbilical artery(Pua). Results: Although we completed 14 newborns, there were only 9 cases of umbilical artery samples and 8 cases of umbilical vein samples were collected. Only 3 cases collected both Pua and Puv blood samples at the same time (see serial paper II). PuaO₂ in gradually decreased with time (heartbeat frequency), until Pua contracted after spontaneous breathing produced about 8~10 heartbeats, and then could not get enough blood samples. Only 3 newborns were able to take blood samples after spontaneous breathing for 8~10 heartbeats, and their PuaO₂ were jumped to 186.0, 137.0 and 93.8 mmHg respectively. The mean value of PuaO₂ was (25.94±6.79, 18.04~37.51)mmHg, the highest value was (29.11±6.46, 23.00~45.90)mmHg, and the lowest value was (21.34±5.54, 14.00~33.60)mmHg. Although PuvO₂ decreased gradually with time (heartbeat) too, most of them also showed the tendency of alternately rising and falling with the regularity of mother's respiration. The mean value of PuvO₂ was (53.35±21.35, 32.56~100.73)mmHg, the highest value was (90.38±48.44, 43.40~153.00)mmHg, and the lowest value was (36.96±14.90, 24.80~73.80)mmHg. Although there were large individual differences, the mean, highest and lowest values of PuvO₂ were significantly higher than those of PuaO₂ (P<0.05); although PuvCO₂ slightly lower than PuaCO₂, it was no significant difference (P>0.05). Conclusion: PuaO₂ decreases gradually with time before spontaneous breathing after the delivered fetus as a newborn, and it induces the first inhalation to start spontaneous breathing when it reaches the threshold of triggering breathing.