Lang Justin A R, Pearson James T, Binder-Heschl Corinna, Wallace Megan J, Siew Melissa L, Kitchen Marcus J, Te Pas Arjan B, Lewis Robert A, Polglase Graeme R, Shirai Mikiyasu, Hooper Stuart B
The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.
Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
J Physiol. 2017 Mar 1;595(5):1593-1606. doi: 10.1113/JP273682. Epub 2017 Feb 14.
Lung aeration at birth significantly increases pulmonary blood flow, which is unrelated to increased oxygenation or other spatial relationships that match ventilation to perfusion. Using simultaneous X-ray imaging and angiography in near-term rabbits, we investigated the relative contributions of the vagus nerve and oxygenation to the increase in pulmonary blood flow at birth. Vagal denervation inhibited the global increase in pulmonary blood flow induced by partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect. The results of the present study indicate that a vagal reflex may mediate a rapid global increase in pulmonary blood flow in response to partial lung aeration.
Air entry into the lungs at birth triggers major cardiovascular changes, including a large increase in pulmonary blood flow (PBF) that is not spatially related to regional lung aeration. To investigate the possible underlying role of a vagally-mediated stimulus, we used simultaneous phase-contrast X-ray imaging and angiography in near-term (30 days of gestation) vagotomized (n = 15) or sham-operated (n = 15) rabbit kittens. Rabbits were imaged before ventilation, when one lung was ventilated (unilateral) with 100% nitrogen (N ), air or 100% oxygen (O ), and after all kittens were switched to unilateral ventilation in air and then ventilation of both lungs using air. Compared to control kittens, vagotomized kittens had little or no increase in PBF in both lungs following unilateral ventilation when ventilation occurred with 100% N or with air. However, relative PBF did increase in vagotomized animals ventilated with 100% O , indicating the independent stimulatory effects of local oxygen concentration and autonomic innervation on the changes in PBF at birth. These findings demonstrate that vagal denervation inhibits the previously observed increase in PBF with partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect.
出生时肺通气显著增加肺血流量，这与氧合增加或其他使通气与灌注相匹配的空间关系无关。我们利用近足月兔同时进行X射线成像和血管造影，研究了迷走神经和氧合对出生时肺血流量增加的相对贡献。迷走神经切断术抑制了部分肺通气引起的肺血流量整体增加，尽管高吸入氧浓度可部分减轻这种效应。本研究结果表明，迷走神经反射可能介导了对部分肺通气的快速肺血流量整体增加。
出生时空气进入肺部会引发主要的心血管变化，包括肺血流量（PBF）大幅增加，且与局部肺通气在空间上无关。为了研究迷走神经介导刺激的潜在作用，我们对近足月（妊娠30天）的兔仔进行迷走神经切断术（n = 15）或假手术（n = 15），并同时进行相衬X射线成像和血管造影。在通气前、当一侧肺用100%氮气（N）、空气或100%氧气（O）进行通气（单侧）时以及所有兔仔都改为单侧空气通气然后双侧肺用空气通气后对兔进行成像。与对照兔仔相比，当用100% N或空气进行通气时，迷走神经切断的兔仔在单侧通气后双肺的PBF几乎没有增加或没有增加。然而，用100% O通气的迷走神经切断动物的相对PBF确实增加了，表明局部氧浓度和自主神经支配对出生时PBF变化具有独立的刺激作用。这些发现表明，迷走神经切断术抑制了之前观察到的部分肺通气时PBF的增加，尽管高吸入氧浓度可部分减轻这种效应。
