The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.
The Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria, Australia.
J Appl Physiol (1985). 2021 Sep 1;131(3):997-1008. doi: 10.1152/japplphysiol.00918.2020. Epub 2021 Aug 5.
Approximately 53% of near-term newborns admitted to intensive care experience respiratory distress. These newborns are commonly delivered by cesarean section and have elevated airway liquid volumes at birth, which can cause respiratory morbidity. We investigated the effect of providing respiratory support with a positive end-expiratory pressure (PEEP) of 8 cmHO on lung function in newborn rabbit kittens with elevated airway liquid volumes at birth. Near-term rabbits (30 days; term = 32 days) with airway liquid volumes that corresponded to vaginal delivery (∼7 mL/kg, control, = 11) or cesarean section [∼37 mL/kg; elevated liquid (EL), = 11] were mechanically ventilated (tidal volume = 8 mL/kg). The PEEP was changed after lung aeration from 0 to 8 to 0 cmHO (control, = 6; EL, = 6), and in a separate group of kittens, PEEP was changed after lung aeration from 8 to 0 to 8 cmHO (control, = 5; EL, = 5). Lung function (ventilator parameters, compliance, lung gas volumes, and distribution of gas within the lung) was evaluated using plethysmography and synchrotron-based phase-contrast X-ray imaging. EL kittens initially receiving 0 cmHO PEEP had reduced functional residual capacities and lung compliance, requiring higher inflation pressures to aerate the lung compared with control kittens. Commencing ventilation with 8 cmHO PEEP mitigated the adverse effects of EL, increasing lung compliance, functional residual capacity, and the uniformity and distribution of lung aeration, but did not normalize aeration of the distal airways. Respiratory support with PEEP supports lung function in near-term newborn rabbits with elevated airway liquid volumes at birth who are at a greater risk of suffering respiratory distress. Term babies born by cesarean section have elevated airway liquid volumes, which predisposes them to respiratory distress. Treatments targeting molecular mechanisms to clear lung liquid are ineffective for term newborn respiratory distress. We showed that respiratory support with an end-expiratory pressure supports lung function in near-term rabbits with elevated airway liquid volumes at birth. This study provides further physiological understanding of lung function in newborns with elevated airway liquid volumes at risk of respiratory distress.
大约 53%的近期新生儿需要进入重症监护病房接受治疗，以缓解呼吸窘迫。这些新生儿通常是通过剖宫产分娩的，出生时气道内液体量增加，这可能导致呼吸疾病。我们研究了在出生时气道内液体量增加的新生兔仔中，给予呼气末正压（PEEP）8 cmH2O 对肺功能的影响。具有与阴道分娩相当的气道液体量（7 mL/kg，对照组，n=11）或剖宫产[37 mL/kg；高液体量（EL）组，n=11]的近足月兔在出生后进行机械通气（潮气量= 8 mL/kg）。在肺充气后，将 PEEP 从 0 增加到 8，再增加到 0 cmH2O（对照组，n=6；EL 组，n=6），并在另一组兔仔中，在肺充气后，将 PEEP 从 8 增加到 0，再增加到 8 cmH2O（对照组，n=5；EL 组，n=5）。使用体积描记法和基于同步辐射的相位对比 X 射线成像来评估肺功能（呼吸机参数、顺应性、肺气体容量和肺内气体分布）。最初接受 0 cmH2O PEEP 的 EL 仔兔的功能残气量和肺顺应性降低，与对照组仔兔相比，需要更高的充气压力才能使肺充气。在通气开始时使用 8 cmH2O PEEP 可以减轻 EL 的不良影响，增加肺顺应性、功能残气量以及肺充气的均匀性和分布，但不能使远端气道充气正常化。PEEP 支持通气可以为出生时气道液体量增加的近期新生儿提供呼吸支持，这些新生儿有发生呼吸窘迫的风险。经剖宫产出生的足月婴儿气道液体量增加，容易发生呼吸窘迫。针对清除肺液的分子机制的治疗方法对足月新生儿呼吸窘迫无效。我们发现，呼气末正压支持通气可以为出生时气道液体量增加的近足月兔提供肺功能支持。这项研究为有发生呼吸窘迫风险的气道液体量增加的新生儿的肺功能提供了进一步的生理学理解。
