Changes in the Pulmonary Circulation during Birth-Related Events

Teitel, David; Iwamoto, Harriet S.; Rudolph, Abraham M.

doi:10.1203/00006450-199004000-00010

Cited by 163 publications

(135 citation statements)

References 11 publications

(22 reference statements)

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“…Ventilation with nitrogen (mechanical ventilation without any change in PaO 2 but decrease in PaCO 2 ) resulted in two-thirds of the decrease in PVR as air ventilation. Unlike the Dawes study, these results clearly indicate that air ventilation is more effective than nitrogen ventilation and are similar to those reported by Teitel et al (6). However, the effect of an intermediate level of O 2 was not tested in any of these studies.…”

Section: Discussionsupporting

confidence: 61%

“…Some studies indicate that ventilation with nitrogen, air, and O 2 are similarly effective in reducing fetal PVR in lambs (4,5). Other studies indicate that PVR drops more effectively with 100% O 2 (6) or air (7,8) than with a nitrogen-rich gas. It may be important to find an intermediate level of O 2 that has the advantages of short-term reduction in PVR without the toxicity of 100% O 2 (9,10).…”

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confidence: 99%

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Pulmonary Hemodynamics in Neonatal Lambs Resuscitated with 21%, 50%, and 100% Oxygen

et al. 2007

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ABSTRACT:The effect of resuscitation with varying levels of O 2 on pulmonary hemodynamics at birth is not well known. We hypothesized that the decrease in pulmonary vascular resistance (PVR) and subsequent response to pulmonary vasoconstrictors and vasodilators will differ following resuscitation with 21%, 50%, or 100%O 2 for 30 min at birth in normal term lambs. Lambs at 141 d gestation were delivered by cesarean section and ventilated with 21% (21% Res; n ϭ 6), 50% (50% Res; n ϭ 6), or 100% O 2 (100% Res; n ϭ 7) for 30 min followed by ventilation with 21% O 2 in all three groups. A greater decrease in PVR was seen with 50% and 100% O 2 ventilation than with 21% O 2 (0.21 Ϯ 0.02, 0.21 Ϯ 0.02, and 0.34 Ϯ 0.05 mm Hg/mL/min/kg, respectively). Subsequent pulmonary vasoconstriction to hypoxia (10% O 2 ) and the thromboxane analog U46619 (0.5 and 1 g/kg/min) was similar in all three groups. After inducing a stable elevation in PVR with U46619, impaired pulmonary vasodilation to inhaled NO (59 Ϯ 4, 65 Ϯ 4, and 74 Ϯ 5% of baseline PVR with 21, 50, and 100%Res, respectively) and acetylcholine infusion (67 Ϯ 8, 75 Ϯ 6, and 87 Ϯ 4% of baseline PVR with 21, 50, and 100%Res, respectively) and rebound pulmonary hypertension following their withdrawal were observed in the 100%Res group. We conclude that, while ventilation with 100% O 2 at birth results in a greater initial decrease in PVR, subsequent pulmonary vasodilation to NO/acetylcholine is impaired. (Pediatr Res 62: 313-318, 2007) F etal pulmonary vascular resistance is high and O 2 plays a crucial role in mediating the pulmonary vascular transition at birth (1). However, the optimal level of O 2 supplementation during resuscitation of a newborn infant remains controversial (2) despite publication of new guidelines (3). During resuscitation of a depressed newborn infant with potentially high PVR, there is concern that room air resuscitation may result in inadequate pulmonary vasodilation. It has been suggested that breathing 100% O 2 dilates constricted pulmonary arteries more efficiently than room air.Previous studies have demonstrated conflicting results regarding the effect of ventilation with different gas mixtures on PVR. Some studies indicate that ventilation with nitrogen, air, and O 2 are similarly effective in reducing fetal PVR in lambs (4,5). Other studies indicate that PVR drops more effectively with 100% O 2 (6) or air (7,8) than with a nitrogen-rich gas. It may be important to find an intermediate level of O 2 that has the advantages of short-term reduction in PVR without the toxicity of 100% O 2 (9,10). Recent studies examined pulmonary hemodynamic responses to 21% or 100% O 2 ventilation, but were conducted on hypoxemic lambs only after 12-72 h of age, after PVR had dropped from high fetal levels immediately after birth (11)(12)(13). Understanding the precise pulmonary hemodynamic response to ventilation with room air, 100% O 2 , and an intermediate level of O 2 exposure (such as 50% O 2 ) in animals at birth is vital for determining the safest protocol ...

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Section: Discussionsupporting

confidence: 61%

mentioning

confidence: 99%

Pulmonary Hemodynamics in Neonatal Lambs Resuscitated with 21%, 50%, and 100% Oxygen

et al. 2007

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“…These include the release of potent vasodilators such as NO and prostacyclin (30), increased oxygen tension, and the mechanical effect of ventilation (10,18). The latter likely results from changes in the distribution of force within perialveolar tissue caused by lung aeration, the formation of surface tension, and the resulting increase in lung recoil (8,32,33).…”

Section: Discussionmentioning

confidence: 99%

“…Waveform parameters examined were mean diastolic PBF and end-diastolic left PBF, as previously described (8). PVR was calculated using the formula PVR ϭ PPA Ϫ PLA/QP, where PPA is pulmonary arterial pressure, PLA is left arterial pressure, and QP is flow through the left pulmonary artery; PLA was assumed to be 3 mm Hg in the fetus and 9 mm Hg in the lamb based on previous studies (6,8,18). mRNA analysis.…”

Section: Methodsmentioning

confidence: 99%

Antenatal Corticosteroids Increase Fetal, But Not Postnatal, Pulmonary Blood Flow in Sheep

et al. 2009

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ABSTRACT:The lungs of very preterm infants have immature airways and gas exchange structures and are usually surfactant deficient. Antenatal corticosteroids are commonly used to enhance fetal lung maturation in preterm infants, but little is known of their effects on pulmonary blood flow (PBF) before and immediately after birth. Our aim was to determine the effects of antenatal betamethasone on PBF before birth and during the postnatal transition in very preterm lambs. Antenatal betamethasone treatment significantly increased mean fetal PBF from 20.2 Ϯ 5.1 to 84.3 Ϯ 18.3 mL/min at 30 h after administration; the PBF waveform was also significantly altered. Mean diastolic PBF increased from Ϫ38.5 Ϯ 4.9 pretreatment to Ϫ10.2 Ϯ 11.0 mL/min at ϳ36 h after the initial betamethasone dose (negative values indicate retrograde flow away from the lungs). Within 10 min after delivery, PBF was similar in control and betamethasone-treated lambs. These data demonstrate that antenatal betamethasone significantly increases fetal PBF and alters the PBF waveform but has little effect on postnatal PBF.

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“…However, at the time of birth, with ventilation assumed by the lungs, dramatic changes in pulmonary circulation occur: pulmonary vascular resistance falls rapidly and pulmonary arterial blood flow increases approximately 8-to 10-fold (Heymann, 1999;Heymann and Soifer, 1989;Teitel et al, 1990). The control of the pulmonary vascular tone both in the fetus and during the transitional period to air-breathing is dependent on a complex and interactive group of mechanisms, including mechanical influences (e.g., endothelial shear stress, physical expansion, alveolar pO 2 ) and a variety of endogenous vasoactive substances produced by the pulmonary vascular endothelium and released locally or into the circulation.…”

Section: Am and Perinatal Adaptationmentioning

confidence: 99%

Adrenomedullin in mammalian embryogenesis

Garayoa

Bodegas

Cuttitta

et al. 2002

Microscopy Res & Technique

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Here are summarized data supporting that adrenomedullin (AM) is a multifunctional factor involved in the complex regulatory mechanisms of mammalian development. During rodent embryogenesis, AM is first expressed in the heart, followed by a broader but also defined spatio-temporal pattern of expression in vascular, neural, and skeletal-forming tissues as well as in the main embryonic internal organs. AM pattern of expression is suggestive of its involvement in the control of embryonic invasion, proliferation, and differentiation processes, probably through autocrine or paracrine modes of action. AM levels in fetoplacental tissues, uterus, maternal and umbilical plasma are highly increased during normal gestation. These findings in addition to other physiological and gene targeting studies support the importance of AM as a vasorelaxant factor implicated in the regulation of maternal vascular adaptation to pregnancy, as well as of fetal and fetoplacental circulations. AM is also present in amniotic fluid and milk, which is suggestive of additional functions in the maturation and immunological protection of the fetus. Altered expression of AM has been found in some gestational pathologies, although it is not yet clear whether this corresponds to causative or compensatory mechanisms. Future studies in regard to the distribution and expression levels of the molecules known to function as AM receptors, together with data on the action of complement factor H (an AM binding protein), may help to better define the roles of AM during embryonic development.

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Changes in the Pulmonary Circulation during Birth-Related Events

Cited by 163 publications

References 11 publications

Pulmonary Hemodynamics in Neonatal Lambs Resuscitated with 21%, 50%, and 100% Oxygen

Pulmonary Hemodynamics in Neonatal Lambs Resuscitated with 21%, 50%, and 100% Oxygen

Antenatal Corticosteroids Increase Fetal, But Not Postnatal, Pulmonary Blood Flow in Sheep

Adrenomedullin in mammalian embryogenesis

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