Sandhar B K, Niblett D J, Argiras E P, Dunnill M S, Sykes M K
Nuffield Department of Anaesthetics, Radcliffe Infirmary, Oxford, UK.
Intensive Care Med. 1988;14(5):538-46. doi: 10.1007/BF00263527.
Sixteen rabbits were anaesthetized and subjected to saline lavage of the lungs to produce surfactant deficiency. This resulted in an arterial oxygen tension of less than 12 kPa on 100% inspired oxygen and an inflection point on the pressure-volume curve at a pressure of 8-12 mmHg. After lavage the animals were randomly assigned to receive either conventional mechanical ventilation (CMV) with a positive end-expiratory pressure (PEEP) of 1-2 mmHg (group I - low PEEP) or CMV with PEEP equal to the inflection point pressure (group II - high PEEP). Mean airway pressures were kept at 14-16 mmHg in both groups by increasing the inspiratory:expiratory time ratios in the low PEEP group. The 5-h protocol was completed by 4 animals in group I and 6 animals in group II, early death usually being associated with a metabolic acidosis. On 100% oxygen, the mean PaO2 at 2-h post-lavage was 15.2 +/- 8.3 kPa in group I and 39.6 +/- 21.8 kPa in group II. Group I had much lower end-expiratory lung volumes (3.0 +/- 1.5 ml above FRC) than group II (34.9 +/- 12.2 ml above FRC). Histological examination of the lungs revealed significantly less hyaline membrane formation in group II (p = 0.001). Thus, the prevention of alveolar collapse by the use of high PEEP levels appears to reduce lung damage in this preparation.
16只兔子被麻醉，并对其肺部进行生理盐水灌洗以造成表面活性剂缺乏。这导致在吸入100%氧气时动脉血氧分压低于12 kPa，且压力-容积曲线上在8 - 12 mmHg压力处出现一个拐点。灌洗后，动物被随机分配接受呼气末正压（PEEP）为1 - 2 mmHg的传统机械通气（CMV）（I组 - 低PEEP）或PEEP等于拐点压力的CMV（II组 - 高PEEP）。通过增加低PEEP组的吸呼时间比，使两组的平均气道压力均保持在14 - 16 mmHg。I组4只动物和II组6只动物完成了5小时的实验方案，早期死亡通常与代谢性酸中毒有关。在吸入100%氧气时，灌洗后2小时I组的平均动脉血氧分压为15.2±8.3 kPa，II组为39.6±21.8 kPa。I组的呼气末肺容积（高于功能残气量3.0±1.5 ml）比II组（高于功能残气量34.9±12.2 ml）低得多。肺部组织学检查显示II组的透明膜形成明显较少（p = 0.001）。因此，在这种实验模型中，使用高水平PEEP预防肺泡塌陷似乎能减少肺损伤。
