Gershan W M, Jacobi M S, Thach B T
Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110.
J Appl Physiol (1985). 1992 Feb;72(2):677-85. doi: 10.1152/jappl.1992.72.2.677.
Mechanisms underlying failure of autoresuscitation from hypoxic apnea were investigated. Failure was induced by repeated exposure to hypoxia. The influence of maturation was studied in adults, weanlings, and 10- and 5-day-old mice. Mice successful at autoresuscitation (BALB/c) as well as those prone to autoresuscitation failure (SWR weanlings) were studied. Hypoxic apnea was induced with 97% N2-3% CO2, and 21% O2 was given at its onset; electrocardiogram and ventilation were recorded. Hypoxic exposure was repeated if autoresuscitation (recovery of eupnea) occurred. Autoresuscitation failure (death) was induced in all mice. Young BALB/c mice tolerated more trials than older mice. SWR weanlings frequently failed to autoresuscitate on the initial exposure and tolerated fewer repeat trials overall than age-matched BALB/c mice. Induced autoresuscitation failure in all mice appeared to be unrelated to gasping regulation, because both gasp number and amplitude were similar during the failed trial and the previous successful trial. In most mice, failure was associated with absent recovery of heart rate during gasping. In BALB/c mice in particular, this persistent bradycardia was usually due to heart block, which occurred in 95% of failed trials. In addition, heart block occurred with increasing frequency on later successful trials, but conversion to sinus rhythm always preceded successful autoresuscitation. Heart block was also frequent in SWR mice and had similar consequences. BALB/c mice exposed to continuous anoxia survived longer than SWR mice, indicating increased endurance of components of the autoresuscitation mechanism not directly related to the ventilatory function of gasping (e.g., cardiovascular components).(ABSTRACT TRUNCATED AT 250 WORDS)
对缺氧性呼吸暂停自主复苏失败的潜在机制进行了研究。通过反复暴露于缺氧环境诱导失败。在成年小鼠、断奶小鼠以及10日龄和5日龄小鼠中研究了成熟度的影响。研究了自主复苏成功的小鼠（BALB/c）以及易于自主复苏失败的小鼠（SWR断奶小鼠）。用97%N₂ - 3%CO₂诱导缺氧性呼吸暂停，并在发作时给予21%O₂；记录心电图和通气情况。如果发生自主复苏（恢复正常呼吸），则重复缺氧暴露。所有小鼠均诱导出自主复苏失败（死亡）。年轻的BALB/c小鼠比年长小鼠能耐受更多次试验。SWR断奶小鼠在初次暴露时经常无法自主复苏，总体上比年龄匹配的BALB/c小鼠耐受的重复试验次数更少。所有小鼠诱导出的自主复苏失败似乎与喘气调节无关，因为在失败试验和之前的成功试验中，喘气次数和幅度都相似。在大多数小鼠中，失败与喘气时心率未恢复有关。特别是在BALB/c小鼠中，这种持续性心动过缓通常是由于心脏传导阻滞，在95%的失败试验中发生。此外，在随后的成功试验中，心脏传导阻滞发生的频率增加，但在成功自主复苏之前总是先转变为窦性心律。心脏传导阻滞在SWR小鼠中也很常见且后果相似。暴露于持续缺氧环境的BALB/c小鼠比SWR小鼠存活时间更长，表明自主复苏机制中与喘气通气功能无直接关系的成分（如心血管成分）的耐力增强。（摘要截断于250字）
