An Initial Sustained Inflation Improves the Respiratory and Cardiovascular Transition at Birth in Preterm Lambs

Abstract

A sustained inflation (SI) facilitates lung aeration after birth but may impair the neonatal cardiovascular transition. We aimed to determine the effect of an initial SI on pulmonary arterial and carotid blood flow (PBF and CBF) after preterm birth. Fetal sheep were instrumented at ϳ122 d of gestation (d). Lambs were delivered at ϳ127 d and received either an initial SI (40 cm H 2 O for 1 min or until a volume of 20 mL/kg was administered) followed by ventilation for 30 min (SI; n ϭ 7) or ventilation for 30 min (non-SI; n ϭ 6). At 10 min after ventilation onset, inspired O 2 content increased from 21 to 100% for 10 min. PBF, CBF, pulmonary arterial and carotid pressures, tidal volume, and inspiratory pressures were recorded. PBF was greater during the SI (p Ͻ 0.05) but thereafter was similar between groups. Non-SI lambs were hypoxemic and had higher CBF than SI lambs (p Ͻ 0.05). Cerebral oxygen delivery was constant in SI lambs but increased ϳ4-fold in non-SI lambs during ventilation with 100% O 2 (p Ͻ 0.05). Lung compliance and respiratory status were better in SI than non-SI lambs (p Ͻ 0.05). A SI improved lung function without adverse circulatory effects, seemed to stabilize neonatal cerebral O 2 delivery, and may protect against cerebral hyperoxia. (Pediatr Res 70: 56-60, 2011)

Respiratory support for premature neonates in the delivery room: effects on cardiovascular function and the development of brain injury

“…Review apart from reduced vascular permeability (Figure 4) (4,48), suggesting that simply improving the initial respiratory care in the delivery room may reduce brain injury.…”

The interrelationship of recruitment maneuver at birth, antenatal steroids, and exogenous surfactant on compliance and oxygenation in preterm lambs

“…PEEP is essential in the preterm lung (5,14). In our study, we used a PEEP (8 cmH 2 O) previously shown to be appropriate in preterm lambs (6,11,16,17), and higher than that used in similar animal studies (5,9,10,14,15,20,29), suggesting our results are due to differences in recruitment strategy and not subsequent ventilator management.…”

“…In our study using intubated preterm lambs, we systematically describe the interrelationship between the use of antenatal corticosteroids, exogenous surfactant therapy, and two distinct recruitment strategies applied Unlike previous animal studies of respiratory care at birth (6,(10)(11)(12)15,16,(20)(21)(22)(27)(28)(29)(30), our study involved a large sample size. Pooling all epochs, the use of an OLV stepwise PEEP approach significantly improved C dyn and oxygenation compared to a 30-s 40 cmH 2 O SI.…”

“…We have recently shown that there is considerable variability in the spatiotemporal behavior of lung mechanics at birth, even in controlled preclinical experiments (6,12,23). Although our choice of SI parameters is based on previous work (9,10,12,20,27,29), it is likely that some of our lambs required a longer SI duration. Our results may reflect insufficient regional aeration, a situation clinicians currently have no bedside tools to rapidly detect during a SI.…”

“…Although both the OLV and SI strategy could be practically applied using a facemask and a variable pressure system (such as the Neopuff), we elected to use an intubated model to ensure standardization of the strategy effect. Common to other preterm lamb studies, lung fluid was passively drained before birth to better replicate the human scenario (6,13,17,23,29), but the residual volume in the lung needing to be overcome during aeration cannot be known. This further emphasizes the need for sufficiently powered animal studies.…”