Effects of Gestation and Antenatal Steroid on Airway and Tissue Mechanics in Newborn Lambs

Pillow, J. Jane; Hall, Graham L.; Willet, Karen E.; Jobe, Alan H.; Hantos, Zoltán; Sly, Peter D.

doi:10.1164/ajrccm.163.5.9906098

Cited by 38 publications

(33 citation statements)

References 32 publications

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“…ratory mechanics related to fetal lung maturation, as assessed in preterm lambs of differing gestations and/or exposure to maternal corticosteroid administration, are also most evident in the parameters of tissue resistance and tissue elastance (21). The observations are consistent with rapid development of the lung tissue occurring during the early neonatal period.…”

Section: Lung Function In Unsedated Newbornssupporting

confidence: 52%

Partitioning of Airway and Parenchymal Mechanics in Unsedated Newborn Infants

Pillow

Stocks²,

Sly

et al. 2005

Pediatr Res

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Section: Lung Function In Unsedated Newbornssupporting

confidence: 52%

Partitioning of Airway and Parenchymal Mechanics in Unsedated Newborn Infants

Pillow

Stocks²,

Sly

et al. 2005

Pediatr Res

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“…Flow during HFOV was measured using a hot-wire anemometer (Florian, Acutronic Medical Systems AG, Hirzel, Switzerland) placed between the distal end of the patient circuit and the TT. Partitioned lung mechanics were evaluated in the lambs at 1 h of age using a modification of the low-frequency forced oscillation technique as described previously (18). C ti was calculated from the coefficients of G and H determined from the forced oscillatory impedance data (19) as follows:…”

Section: Methodsmentioning

confidence: 99%

Dependence of Intrapulmonary Pressure Amplitudes on Respiratory Mechanics during High-Frequency Oscillatory Ventilation in Preterm Lambs

Pillow

2002

Pediatric Research

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In the healthy animal lung, high-frequency oscillatory ventilation (HFOV) achieves effective ventilation at tidal volumes (V T ) less than or equal to dead space while generating very small pressure fluctuations in the alveolar spaces (⌬P A ). We hypothesized that the respiratory mechanical parameters influence the magnitude of the intrapulmonary pressure fluctuations during HFOV. A computer model of the neonatal respiratory system was used to examine the independent effects of altering the compliance, nonlinear and linear resistance, and inertance of the respiratory system on V T , and cyclic intrapulmonary pressures under homogeneous and heterogeneous conditions. The impact of low compliance on the transmission of pressure from the airway opening to the trachea (⌬P tr /⌬P ao ) and alveolar compartment (⌬P A /⌬P ao ) during HFOV was determined in a preterm lamb lung model. In the computer model, an increase in flow-dependent resistance to simulate changing the internal diameter of the tracheal tube from 4.0 mm to 2.5 mm halved the transmission of the pressure waveform to both the carina and the alveolar compartment. Increased peripheral resistance was associated with an increased ⌬P tr /⌬P ao but a reduction in ⌬P A /⌬P ao . The ⌬P A /⌬P ao also decreased with increasing alveolar compartment compliance, a finding that was verified in the preterm lamb lung. There was an exponential decrease in the magnitude of ⌬P A1 compared with ⌬P A2 as the ratio of the time constants of the two parallel compartments ( 1 / 2 ) increased in the heterogeneous computer lung model. The transmission of driving pressure amplitude to both the proximal airways and lung tissue during HFOV is dependent on lung mechanics and may be greater in the poorly compliant lung than that One of the purported advantages of HFOV is the achievement of adequate gas exchange at low intrapulmonary pressure amplitudes and V T . At least in theory, HFOV should reduce the potential barotrauma and volutrauma that are commonly associated with more conventional ventilatory modalities and which may be vitally important in the structurally and functionally immature preterm lung. The experimental evidence supporting the generation of small ⌬P A during HFOV was obtained in healthy adult rabbits (1) and excised adult dog lungs (2). Only one study has obtained direct measurements of ⌬P A in both a normal and abnormal lung model (3). Although Received December 31, 2001; accepted March 26, 2002

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“…45,70,98,126 Of these factors, based on our animal data and human data from previous studies dealing with preterm gestations, it appears that the most effective strategy for accelerating reabsorption of fetal lung fluid would be the administration of exogenous glucocorticoids. 43,48,83,111 High doses of glucocorticoids have been shown to stimulate transcription of ENaC in several sodium transporting epithelia as well as in the lung. 126 In the alveolar epithelia, glucocorticoids were found to induce lung sodium reabsorption in the late gestation fetal lung.…”

Section: What Causes the Neonatal Lung Epithelium To Switch To An Absmentioning

confidence: 99%

“…70 In addition, steroids have been shown to have beneficial effects on the surfactant system as well as pulmonary mechanics. 43,74,111,121,133,134 …”

Section: What Causes the Neonatal Lung Epithelium To Switch To An Absmentioning

confidence: 99%

Elective Cesarean Section: Its Impact on Neonatal Respiratory Outcome

Ramachandrappa¹,

Jain²

2008

Clinics in Perinatology

158

108

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The transition from a fluid filled lung to one filled with air in a very short period of time is one of the biggest challenges a newborn faces after birth. Respiratory morbidity as a result of failure to clear fetal lung fluid is not uncommon, and can be particularly problematic in some infants delivered by elective cesarean section (ECS) without being exposed to labor. The increasing rates of cesarean deliveries in the United States and worldwide, have the potential for a significant impact on public health and health care costs due to the morbidity associated with this subgroup. Whereas the occurrence of birth asphyxia, trauma, and meconium aspiration is reduced by elective cesarean delivery, the risk of respiratory distress secondary to transient tachypnea of the newborn, surfactant deficiency, and pulmonary hypertension is increased. It is clear that physiologic events in the last few weeks of pregnancy coupled with the onset of spontaneous labor are accompanied by changes in the hormonal milieu of the fetus and its mother, resulting in preparation of the fetus for neonatal transition. Rapid clearance of fetal lung fluid is a key part of these changes, and is mediated in large part by transepithelial sodium reabsorption through amiloride-sensitive sodium channels in the alveolar epithelial cells, with only a limited contribution from mechanical factors and Starling forces. In this chapter we discuss the respiratory morbidity associated with ECS, the physiologic mechanisms underlying fetal lung fluid absorption and potential strategies for facilitating neonatal transition when infants are delivered by ECS before the onset of spontaneous labor. The changing landscape for human deliveriesCesarean births rose for an tenth straight year in 2006 to a record 31.1% of all deliveries in the United States; this rate is more than 50% higher than in 1996 and is accompanied by a significant drop in the number of women attempting vaginal birth after a previous cesarean delivery (VBAC). 56 ( Fig. 1) Most of the overall increase can be attributed to the increase in the primary cesarean rates, from 14.6% in 1996 to 20.3% in 2005. This rise in the primary cesarean rate coupled with the decrease in the VBAC rate (7.9% in 2005) means that women who have a primary cesarean section have a greater than 90% chance of having a repeat cesarean section, further increasing the overall cesarean rate in the future. 90 Among the many reasons cited for this increase are older women giving birth, multiple gestations from fertility treatments, as well as the concerns of physicians and mothers about the risks of vaginal birth. Cesarean births in low risk or "no risk" mothers where no medical indication can be identified are on the rise and are often referred to as Cesarean Delivery at Maternal Request (CDMR).Address for Correspondence and Reprints: Lucky Jain, MD, MBA, Professor of Pediatrics & Executive Vice Chairman, Emory University School of Medicine, 2015 Uppergate Drive, Atlanta GA 30322, ljain@emory.edu, 404-727-1471. Coauthor...

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Effects of Gestation and Antenatal Steroid on Airway and Tissue Mechanics in Newborn Lambs

Cited by 38 publications

References 32 publications

Partitioning of Airway and Parenchymal Mechanics in Unsedated Newborn Infants

Partitioning of Airway and Parenchymal Mechanics in Unsedated Newborn Infants

Dependence of Intrapulmonary Pressure Amplitudes on Respiratory Mechanics during High-Frequency Oscillatory Ventilation in Preterm Lambs

Elective Cesarean Section: Its Impact on Neonatal Respiratory Outcome

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