Tepper R S
Indiana University School of Medicine, Department of Pediatrics, Indianapolis.
Pediatr Pulmonol. 1993 Jul;16(1):48-53. doi: 10.1002/ppul.1950160110.
Maximal bronchoconstriction in normal adults produces only small reductions in pulmonary function; however, in normal infants severe airway obstruction limits testing to low agonist concentrations. In this study, maximal pulmonary response to methacholine was evaluated in 5 immature (1 month old) and 5 mature (6 months old) rabbits. Animals were anesthetized, paralyzed, and mechanically ventilated via a tracheostomy tube. Changes in pulmonary function were assessed from maximal deflation flow volume curves following inhalation of doubling concentrations of methacholine between 0.6 and 320 mg/mL. Following 320 mg/mL methacholine, the immature rabbits had a greater percent decline in forced vital capacity (FVC) than the mature animals (55 +/- 15% vs. 36 +/- 10%; P < 0.05). At 50% FVC, isovolume flows were measurable in the 5 mature rabbits, and 4 of 5 had plateaus in their dose-response curves. At the higher methacholine doses, only 1 of 5 immature animals had measurable isovolume flows because of the decrease in FVC. There was no significant difference between immature and mature animals in the methacholine dose required to decrease baseline flows by 50%. We conclude that in rabbits maturation affects maximal pulmonary response but not the sensitivity to methacholine.
正常成年人的最大支气管收缩仅导致肺功能有小幅下降；然而，对于正常婴儿，严重的气道阻塞使得测试只能在低激动剂浓度下进行。在本研究中，评估了5只未成熟（1个月大）和5只成熟（6个月大）兔子对乙酰甲胆碱的最大肺反应。动物经气管切开插管麻醉、麻痹并进行机械通气。在吸入浓度从0.6至320 mg/mL成倍增加的乙酰甲胆碱后，根据最大呼气流量容积曲线评估肺功能变化。吸入320 mg/mL乙酰甲胆碱后，未成熟兔子的用力肺活量（FVC）下降百分比高于成熟动物（55±15%对36±10%；P<0.05）。在50%FVC时，5只成熟兔子的等容积流量可测，且5只中有4只的剂量反应曲线出现平台期。在较高的乙酰甲胆碱剂量下，由于FVC下降，5只未成熟动物中只有1只的等容积流量可测。未成熟和成熟动物使基线流量降低50%所需的乙酰甲胆碱剂量无显著差异。我们得出结论，在兔子中，成熟影响最大肺反应，但不影响对乙酰甲胆碱的敏感性。
