Maturation of interdependence between extra-alveolar arteries and lung parenchyma in piglets.

Mansell, Anthony L.; McAteer, Allison L.; Pipkin, A. C.

doi:10.1161/01.res.71.3.701

Cited by 12 publications

(6 citation statements)

References 17 publications

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“…Two groups of female Duroc piglets were studied: one 3-7 days of age (1.3-2.1 kg body wt), which was designated the "immature" group, and the other 3 mo of age (25-40 kg body wt), which was designated the "mature" group. Age of the immature group was chosen to avoid temporary characteristics of structure and function in freshly newborn piglet lungs (23). Age of the mature group was chosen to avoid the practical difficulties in handling large, fully grown pigs.…”

Section: Methodsmentioning

confidence: 99%

“…Because elastic moduli of the lung parenchyma are also similar in the two age groups, it was concluded that local features of airway-parenchyma coupling limited the generation of local parenchymal recoil around bronchi in the immature lungs. lung growth; airway-parenchyma interdependence; bronchograms A PREVIOUS STUDY DOCUMENTED remarkable behavior of extra-alveolar blood vessels during inflation of excised immature piglet lungs (23). Lung inflation compressed these vessels, in contrast to the decompression that had been observed consistently during inflation of excised mature lungs from several species (1,13,17,29,33).…”

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confidence: 99%

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Mechanical dissociation of bronchi from parenchyma in the immature piglet lung

Mansell

McAteer

Oldmixon

2000

Journal of Applied Physiology

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Previous studies of isolated piglet lungs suggested that local distending forces around bronchi might be relatively weak before postnatal growth and maturation. The present study used tantalum bronchograms to compare pressure-diameter relationships of bronchi in situ and after excision from the parenchyma in immature (3- to 7-day-old) and mature (3-mo-old) piglets. The mature group reproduced behavior that is well established in mature lungs from other species; i.e., bronchial diameters maintained a constant relationship to the parenchyma as the lungs were deflated from maximum to minimum volume. In sharp contrast, diameters failed to change until the immature lungs were deflated to <5 cmH(2)O transpulmonary pressure. Total percent change in bronchial diameter was then only 24% in the immature lungs compared with 47% in the mature lungs (P < 0.002). Total elastances of mature generation 3-8 bronchi did not change when they were excised from the parenchyma. However, in the same generations of immature bronchi, total elastances were lower after than before (1.06 vs. 1.60 cmH(2)O/%, P < 0.05) excision from the parenchyma. Elastances of the excised immature and mature bronchi were then the same (1.06 vs. 1.03 cmH(2)O/%, not significant). Because elastic moduli of the lung parenchyma are also similar in the two age groups, it was concluded that local features of airway-parenchyma coupling limited the generation of local parenchymal recoil around bronchi in the immature lungs.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Mechanical dissociation of bronchi from parenchyma in the immature piglet lung

Mansell

McAteer

Oldmixon

2000

Journal of Applied Physiology

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“…However, the transpulmonary pressure and lung volume at which airway closure occurs is dependent on the forces applied to bronchi, for example from parenchymal interdependence, as well as the mechanical properties of the bronchi themselves [18][19][20][21]. Elastic recoil pressures of immature lungs are low compared to adults [19,21,24], suggesting that the forces resisting bronchial closure may be less in the infant than the adult.…”

Section: Pressure Induced Airway Closurementioning

confidence: 99%

Effect of transmural pressure on preloads and collapse of immature bronchi

McFawn¹,

Mitchell²

1997

Eur Respir J

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Immature airways are highly compliant compared to the adult, suggesting that trachea and bronchi from immature animals may be easily compressed. Although tracheal compression has been extensively studied, the effect of transmural pressure on occlusion of immature bronchi has been neglected.The transmural pressure at which the lumen closed was determined from the transmittance of pressure along the lumen of isolated bronchi from late-term foetal, 1 and 4 week old pigs. Bronchi from eight cases of sudden infant death syndrome (SIDS) were also studied. In several experiments, smooth muscle tone was produced either by electrical field stimulation or carbachol challenge, and the relationship between active muscle tone and resting transmural pressure was studied.Bronchi from foetal, 1 and 4 week old pigs were occluded by intraluminal pressures of -4, -5 and -24 cmH 2 O. SIDS bronchi closed at -11 cmH 2 O. Histological and endoscopic investigations showed that closure of the bronchi occurred along a plane and was not uniform along the bronchus. Carbachol precontraction increased the transmural pressure required to close bronchi by approximately 5 cmH 2 O. The relationship between muscle tone and resting pressure was the same in all age groups, except when transmural pressure was at or below closing pressure.Bronchi from immature animals and human infants are vulnerable to collapse by small changes in transmural pressure. Bronchial closure is partly dependent on smooth muscle tone, particularly in younger animals. Eur Respir J 1997; 10: 322-329 The effect of lung forces on the calibre of intrapulmonary airways is strongly influenced by the stability of the airway, which in turn is associated with the structural components of the bronchial wall and with their compliance. Trachea and bronchi from foetal and newborn animals are more compliant than those from older animals [1-3], suggesting that they would be more easily occluded by changes in transmural pressure. For example, flow through isolated segments of foetal lamb (114-121 days gestation) trachea is stopped by an external pressure of approximately 10-15 cmH 2 O [4]. Separate studies suggest that much higher forces are needed to occlude the adult trachea [5][6][7][8].The susceptibility of immature airways in the bronchial tree to transmural forces has not been investigated. Bronchi are structurally different to the trachea and have a continuous layer of smooth muscle, which does not directly insert into the cartilage plates which cover it. This arrangement of cartilage and muscle is likely to give the bronchi mechanical properties different to the trachea. Morphological studies of the trachea and bronchi of adult cats suggest that bronchi are more collapsible than trachea, with considerable distortion of the bronchial wall produced by an intraluminal pressure of -15 cmH 2 O [6].Airway smooth muscle tone can increase the stability of the airway wall. In the neonate and adult, smooth muscle tone reduces airway compliance [9][10][11][12]. Smooth muscle tone ma...

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“…The lung maturation in piglets at birth is advanced compared with human newborns. The airways and associated blood vessels are completely formed at birth, whereas parenchymal development occurs primarily after birth (26). In contrast to the human newborn the chest wall of the newborn piglet is stiff (27).…”

Section: Discussionmentioning

confidence: 99%

Resuscitation of Hypoxic Newborn Piglets With Oxygen Induces a Dose-Dependent Increase in Markers of Oxidation

et al. 2007

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Newborn resuscitation with pure oxygen may be associated with long-term detrimental effects. Due to the change in attitude toward use of less oxygen upon resuscitation, there is a need to study effects of intermediate hyperoxia. The aim was to study dose-response correlation between inspiratory fraction of oxygen used for resuscitation and urinary markers of oxidative damage to DNA and amino acids. Hypoxemia was induced in newborn piglets following a standardized model; they were resuscitated for 15 min with either 21%, 40%, 60% or 100% oxygen and observed for 1 h. Urine samples were collected. Urinary elimination of 8-hydroxy-2=-deoxyguanosine (8-oxo-dG), 2=deoxyguanosine (2dG), orthotyrosine (o-Tyr) and phenylalanine (Phe) were determined by HPLC and tandem mass spectrometry (HPLC-MS/MS). Quotient of 8-oxo-dG/ 2dG and o-Tyr/Phe ratios were significantly and dose-dependant higher in piglets resuscitated with supplementary oxygen. T he transition from fetal to neonatal life contains complex and rapid physiologic changes. Usually, these changes are spontaneous, but approximately 10% of newborn babies require some assistance to begin breathing, and about 1% requires extensive resuscitation (1).Compared with the intrauterine pO 2 at about 3.3 kPa every child comes out to a relative hyperoxia and the values will normally spontaneously rise to about 8kPa during the first 30 min pp. Excessive hyperoxia may disturb a tuned equilibrium in the oxidative-antioxidative system. Exposure to hyperoxia generates significant higher levels of free radicals, and even more when preceded by hypoxia (2).In the neonatal literature an increasing number of studies focusing on supplementary oxygen shows how oxidative stress influences both mortality and morbidity (3,4). Moreover, babies exposed to high oxygen concentrations in the first minutes of postnatal life have been shown to be at higher risk of childhood leukemia and cancer (5,6) making it mandatory to search for the causal connection.We wanted to explore possible reasons for long-term effects of oxidative stress as well as to search for signs of oxidative damage to DNA and proteins and have chosen two biomarkers of oxidative stress; 8-hydroxy-2=-deoxyguanosine (8oxodG) and ortho-tyrosine (o-Tyr). Urinary excretion of modified nucleosides/bases i.e., 8oxodG can be measured to assess oxidative damage on the level of the whole organism (7) and has been used to evaluate oxidative stress in patients (8). O-tyr is known to be formed entirely upon reaction of Phe with hydroxyl radicals and can also be measured in urine (9).In addition, we also wanted to study the effect of re oxygenation with different oxygen concentrations to see if there is a dose-dependency or if there could be a threshold beyond which supplementary oxygen seems to be detrimental.We hypothesized that resuscitation of piglets with supplementary oxygen (40%, 60% or 100%) would cause increased oxidative stress, more reactive oxygen species (ROS), and more damage to proteins and DNA than 21% oxygen. MATERIALS ...

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Maturation of interdependence between extra-alveolar arteries and lung parenchyma in piglets.

Cited by 12 publications

References 17 publications

Mechanical dissociation of bronchi from parenchyma in the immature piglet lung

Mechanical dissociation of bronchi from parenchyma in the immature piglet lung

Effect of transmural pressure on preloads and collapse of immature bronchi

Resuscitation of Hypoxic Newborn Piglets With Oxygen Induces a Dose-Dependent Increase in Markers of Oxidation

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