Bhutani V K, Rubenstein D, Shaffer T H
Pediatr Res. 1981 May;15(5):829-32.
The effect of positive pressure ventilation on the highly compliant fetal airways was evaluated utilizing fetal rabbit tracheal segments. The degree of mechanical and dimensional deformation was quantified to the pressure applied intermittently (IPP) or continuously (CPAP) for 60 min. Excised tracheal segments were obtained at 21, 27, and 31 days fetal rabbit gestation (term = 31 days) and from 18 +/- 6-month-old adults. Internal diameter, resting length, and volume of the tracheal segments were measured, and their pressure-volume relationships were determined by plethysmography. Tracheal specific compliance at deflation pressure of 0 to 10 cm H2O was calculated from these data. In all fetal groups, the application of positive pressure resulted in a decrease of both tracheal distensibility and the slope of the pressure-volume curves; in addition, a highly significant decrease in tracheal specific compliance was documented. At 21 days gestation, the tracheal specific compliance decreased from 0.089 to 0.034 cm H20-1 (P less than 0.001) after CPAP and to 0.025 cm H2O (P less than 0.001) after IPP. For the same group, the resting tracheal volume increased by a dramatic 89% (P less than 0.001) after CPAP and by 124% (P less than 0.001) after IPP. The magnitude of these alterations decreased as gestational age advanced; the changes were not significant by adulthood. These data indicate that significant pressure-induced deformation (barotrauma) is sustained by susceptible immature airways.
利用胎兔气管段评估了正压通气对高顺应性胎儿气道的影响。对间歇性（IPP）或持续性（CPAP）施加60分钟的压力下机械和尺寸变形程度进行了量化。在胎兔妊娠21、27和31天（足月为31天）以及18±6月龄的成年兔中获取切除的气管段。测量气管段的内径、静息长度和体积，并通过体积描记法确定其压力-体积关系。根据这些数据计算0至10 cm H2O放气压力下的气管比顺应性。在所有胎儿组中，正压通气导致气管扩张性和压力-体积曲线斜率均降低；此外，记录到气管比顺应性显著降低。在妊娠21天时，CPAP后气管比顺应性从0.089降至0.034 cm H20-1（P<0.001），IPP后降至0.025 cm H2O（P<0.001）。对于同一组，CPAP后静息气管体积显著增加89%（P<0.001），IPP后增加124%（P<0.001）。随着胎龄增加，这些改变的程度降低；成年后这些变化不显著。这些数据表明，易受影响的未成熟气道会持续承受显著的压力诱导变形（气压伤）。
