Kitchen Marcus J, Siew Melissa L, Wallace Megan J, Fouras Andreas, Lewis Robert A, Yagi Naoto, Uesugi Kentaro, Te Pas Arjan B, Hooper Stuart B
School of Physics, Monash Institute of Medical Research, Clayton, Victoria, Australia.
The Ritchie Centre, Monash Institute of Medical Research, Clayton, Victoria, Australia.
PLoS One. 2014 Apr 1;9(4):e93391. doi: 10.1371/journal.pone.0093391. eCollection 2014.
Current recommendations suggest the use of positive end-expiratory pressures (PEEP) to assist very preterm infants to develop a functional residual capacity (FRC) and establish gas exchange at birth. However, maintaining a consistent PEEP is difficult and so the lungs are exposed to changing distending pressures after birth, which can affect respiratory function. Our aim was to determine how changing PEEP levels alters the distribution of ventilation within the lung. Preterm rabbit pups (28 days gestation) were delivered and mechanically ventilated with one of three strategies, whereby PEEP was changed in sequence; 0-5-10-5-0 cmH2O, 5-10-0-5-0 cmH2O or 10-5-0-10-0 cmH2O. Phase contrast X-ray imaging was used to analyse the distribution of ventilation in the upper left (UL), upper right (UR), lower left (LL) and lower right (LR) quadrants of the lung. Initiating ventilation with 10PEEP resulted in a uniform increase in FRC throughout the lung whereas initiating ventilation with 5PEEP or 0PEEP preferentially aerated the UR than both lower quadrants (p<0.05). Consequently, the relative distribution of incoming VT was preferentially directed into the lower lobes at low PEEP, primarily due to the loss of FRC in those lobes. Following ventilation at 10PEEP, the distribution of air at end-inflation was uniform across all quadrants and remained so regardless of the PEEP level. Uniform distribution of ventilation can be achieved by initiating ventilation with a high PEEP. After the lungs have aerated, small and stepped reductions in PEEP result in more uniform changes in ventilation.
当前的建议表明，使用呼气末正压（PEEP）来帮助极早产儿形成功能残气量（FRC）并在出生时建立气体交换。然而，维持一致的PEEP很困难，因此出生后肺部会暴露于不断变化的扩张压力下，这可能会影响呼吸功能。我们的目的是确定PEEP水平的变化如何改变肺内通气的分布。对早产兔幼崽（妊娠28天）进行分娩，并采用三种策略之一进行机械通气，其中PEEP按顺序变化；0-5-10-5-0厘米水柱、5-10-0-5-0厘米水柱或10-5-0-10-0厘米水柱。使用相衬X射线成像分析肺的左上（UL）、右上（UR）、左下（LL）和右下（LR）象限的通气分布。以10厘米水柱的PEEP开始通气会导致整个肺部的FRC均匀增加，而以5厘米水柱或0厘米水柱的PEEP开始通气时，UR比两个下象限优先通气（p<0.05）。因此，在低PEEP时，进入的潮气量（VT）的相对分布优先导向下叶，这主要是由于这些叶中FRC的丧失。在以10厘米水柱的PEEP通气后，充气末期的空气分布在所有象限都是均匀的，并且无论PEEP水平如何都保持如此。通过以高PEEP开始通气可以实现通气的均匀分布。在肺部通气后，PEEP的小幅逐步降低会导致通气变化更加均匀。
