Hooper Stuart B, Kitchen Marcus J, Siew Melissa L L, Lewis Robert A, Fouras Andreas, te Pas Arjan B, Siu Karen K W, Yagi Naoto, Uesugi Kentaro, Wallace Megan J
Department of Physiology, Royal Women's Hospital, Melbourne, Victoria, Australia.
Clin Exp Pharmacol Physiol. 2009 Jan;36(1):117-25. doi: 10.1111/j.1440-1681.2008.05109.x.
The transition to extra-uterine life at birth is critically dependent on airway liquid clearance to allow the entry of air and the onset of gaseous ventilation. We have used phase contrast X-ray imaging to identify factors that regulate lung aeration at birth in spontaneously breathing term and mechanically ventilated preterm rabbit pups. Phase contrast X-ray imaging exploits the difference in refractive index between air and water to enhance image contrast, enabling the smallest air-filled structures of the lung (alveoli; < 100 microm) to be resolved. Using this technique, the lungs become visible as they aerate, allowing the air-liquid interface to be observed as it moves distally during lung aeration. Spontaneously breathing term rabbit pups rapidly aerate their lungs, with most fully recruiting their functional residual capacity (FRC) within the first few breaths. The increase in FRC occurs mainly during individual breaths, demonstrating that airway liquid clearance and lung aeration is closely associated with inspiration. We suggest that transpulmonary pressures generated by inspiration provide a hydrostatic pressure gradient for the movement of water out of the airways and into the surrounding lung tissue after birth. In mechanically ventilated preterm pups, lung aeration is closely associated with lung inflation and a positive end-expiratory pressure is required to generate and maintain FRC after birth. In summary, phase contrast X-ray imaging can image the air-filled lung with high temporal and spatial resolution and is ideal for identifying factors that regulate lung aeration at birth in both spontaneously breathing term and mechanically ventilated preterm neonates.
出生时向宫外生活的转变严重依赖于气道液体清除，以允许空气进入并开始气体通气。我们使用相衬X射线成像来确定在自然呼吸的足月和机械通气的早产兔幼崽出生时调节肺充气的因素。相衬X射线成像利用空气和水之间的折射率差异来增强图像对比度，从而能够分辨出肺中最小的充气结构（肺泡；<100微米）。使用这种技术，肺在充气时变得可见，从而可以观察到气液界面在肺充气过程中向远端移动。自然呼吸的足月兔幼崽的肺迅速充气，大多数在最初几次呼吸内就完全募集了其功能残气量（FRC）。FRC的增加主要发生在单次呼吸期间，这表明气道液体清除和肺充气与吸气密切相关。我们认为，出生后吸气产生的跨肺压力为水从气道移出并进入周围肺组织提供了一个静水压力梯度。在机械通气的早产幼崽中，肺充气与肺膨胀密切相关，出生后需要呼气末正压来产生和维持FRC。总之，相衬X射线成像可以以高时间和空间分辨率对充气的肺进行成像，非常适合确定在自然呼吸的足月和机械通气的早产新生儿出生时调节肺充气的因素。
