Effects of inertial load and countermeasures on the distribution of pulmonary blood flow

Chornuk, Myron A.; Bernard, Susan L.; Burns, John W.; Glenny, Robb W.; Sheriff, Don D.; Sinclair, Scott E.; Polissar, Nayak L.; Hlastala, Michael P.

doi:10.1152/jappl.2000.89.2.445

Cited by 9 publications

(3 citation statements)

References 35 publications

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“…Since then, a series of studies have corroborated findings of perfusion distribution not easily interpreted within the framework of the four-zone model. For instance, high-resolution imaging of pulmonary perfusion have demonstrated no, or only minute, gravitational flow gradients in the prone position (2,22,28), gravityindependent inequality in pulmonary blood flow (4,5,17,20), fairly fixed perfusion distribution with reduced and increased gravitational force (1,3), and centripetal perfusion gradients (6,22,29), all at least in partial conflict with the zonal paradigm.…”

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confidence: 99%

Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung

Walther¹,

Johansson²,

Flatebø³

et al. 2005

Journal of Applied Physiology

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The classic four-zone model of lung blood flow distribution has been questioned. We asked whether the effect of positive end-expiratory pressure (PEEP) is different between the prone and supine position for lung tissue in the same zonal condition. Anesthetized and mechanically ventilated prone (n = 6) and supine (n = 5) sheep were studied at 0, 10, and 20 cm H2O PEEP. Perfusion was measured with intravenous infusion of radiolabeled 15-microm microspheres. The right lung was dried at total lung capacity and diced into pieces (approximately 1.5 cm3), keeping track of the spatial location of each piece. Radioactivity per unit weight was determined and normalized to the mean value for each condition and animal. In the supine posture, perfusion to nondependent lung regions decreased with little relative perfusion in nondependent horizontal lung planes at 10 and 20 cm H2O PEEP. In the prone position, the effect of PEEP was markedly different with substantial perfusion remaining in nondependent lung regions and even increasing in these regions with 20 cm H2O PEEP. Vertical blood flow gradients in zone II lung were large in supine, but surprisingly absent in prone, animals. Isogravitational perfusion heterogeneity was smaller in prone than in supine animals at all PEEP levels. Redistribution of pulmonary perfusion by PEEP ventilation in supine was largely as predicted by the zonal model in marked contrast to the findings in prone. The differences between postures in blood flow distribution within zone II strongly indicate that factors in addition to pulmonary arterial, venous, and alveolar pressure play important roles in determining perfusion distribution in the in situ lung. We suggest that regional variation in lung volume through the effect on vascular resistance is one such factor and that chest wall conformation and thoracic contents determine regional lung volume.

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confidence: 99%

Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung

Walther¹,

Johansson²,

Flatebø³

et al. 2005

Journal of Applied Physiology

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“…gravity and 1 G. Steeper and statistically significant large-scale gravitationally directed gradients were demonstrable in animal centrifuge studies where larger G forces could be generated (31). Of interest, however, was that even with centrifugeinduced forces of 3-6 G along the head-to-tail z-axis, the addition of a pressure suit to maintain a more normal chest and abdominal wall configuration at high G z forces minimized the high G z effect on the slope of the gravitational gradient within the lung (13).…”

Section: Microsphere Studies Of Large-scale Flow Gradients In the Lungmentioning

confidence: 99%

Microsphere maps of regional blood flow and regional ventilation

Robertson

Hlastala²

2007

Journal of Applied Physiology

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Robertson HT, Hlastala MP. Microsphere maps of regional blood flow and regional ventilation. J Appl Physiol 102: [1265][1266][1267][1268][1269][1270][1271][1272] 2007. First published December 7, 2006; doi:10.1152/japplphysiol.00756.2006.-Systematically mapped samples cut from lungs previously labeled with intravascular and aerosol microspheres can be used to create high-resolution maps of regional perfusion and regional ventilation. With multiple radioactive or fluorescent microsphere labels available, this methodology can compare regional flow responses to different interventions without partial volume effects or registration errors that complicate interpretation of in vivo imaging measurements. Microsphere blood flow maps examined at different levels of spatial resolution have revealed that regional flow heterogeneity increases progressively down to an acinar level of scale. This pattern of scale-dependent heterogeneity is characteristic of a fractal distribution network, and it suggests that the anatomic configuration of the pulmonary vascular tree is the primary determinant of high-resolution regional flow heterogeneity. At ϳ2-cm 3 resolution, the large-scale gravitational gradients of blood flow per unit weight of alveolar tissue account for Ͻ5% of the overall flow heterogeneity. Furthermore, regional blood flow per gram of alveolar tissue remains relatively constant with different body positions, gravitational stresses, and exercise. Regional alveolar ventilation is accurately represented by the deposition of inhaled 1.0-m fluorescent microsphere aerosols, at least down to the ϳ2-cm 3 level of scale. Analysis of these ventilation maps has revealed the same scale-dependent property of regional alveolar ventilation heterogeneity, with a strong correlation between ventilation and blood flow maintained at all levels of scale. The ventilation-perfusion (V A/Q ) distributions obtained from microsphere flow maps of normal animals agree with simultaneously acquired multiple inert-gas elimination technique V A/Q distributions, but they underestimate gas-exchange impairment in diffuse lung injury.ventilation-perfusion ratio; radioactive microspheres; fluorescent microspheres; aerosol IN VIVO PULMONARY IMAGES OF intravenously injected radionuclide-labeled microspheres and radionuclide-labeled aerosol have been part of the clinical diagnostic armamentarium for over 40 years. The resolution of the old in vivo planar gamma camera images was relatively weak, and lung flow mapping techniques using experimental animals were subsequently developed to gain enhanced spatial resolution. The microsphere mapping approach involves in vivo administration of intravascularly injected and/or aerosol labels, followed by fixation of the lung, systematic cutting and mapping of the cut pieces, and measurement of label concentrations in each piece. The spatial perfusion and/or ventilation maps that are reconstructed from these data have been employed in a wide range of experimental studies. This review will address the advantages and lim...

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“…Most of the previous studies carried out by other groups were limited to a maximum acceleration of 5 g z , except for some animal examinations [10]. Furthermore, a mass spectrometer, complex in calibration and operation, has been used in most cases to measure the ventilated gas fractions of the subjects.…”

Section: Introductionmentioning

confidence: 99%

Preliminary results of a miniaturized respiratory sensor system used under hypergravity conditions up to 9g_z

Guenther

Baumann

Meyer

et al. 2013

Meas. Sci. Technol.

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Respiratory gas analyses are used to explore the influence of increased gravity on the physiology of breathing. Due to the mass, size and intricacy of standard measurement systems, previous studies were limited to a maximum acceleration of + 5 gz (head-to-foot direction). Furthermore, no in situ mainstream measurements of oxygen and carbon dioxide concentration were possible under hypergravity conditions so far. This paper shows a first study which demonstrates a respiratory sensor system developed at the Institute for Aerospace Engineering at TU Dresden. This system is suitable for an in situ measurement of respiratory changes up to + 9 gz (maximum acceleration of jet pilots) and therefore provides a possibility for detailed physiological analyses in future. Three jet pilots were equipped with this system and accelerated under a defined profile up to 7, 8 and + 9 gz. The breathing air flow, oxygen and carbon dioxide concentration were recorded with our miniaturized solid state electrolyte gas sensors, which are also described in this paper. The analysed data show significant changes of the measured respiratory parameters depending on the G-level, the acceleration rate (G-rate of onset [g s−1]) and the examination time.

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Effects of inertial load and countermeasures on the distribution of pulmonary blood flow

Cited by 9 publications

References 35 publications

Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung

Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung

Microsphere maps of regional blood flow and regional ventilation

Preliminary results of a miniaturized respiratory sensor system used under hypergravity conditions up to 9g_z

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Effects of inertial load and countermeasures on the distribution of pulmonary blood flow

Cited by 9 publications

References 35 publications

Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung

Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung

Microsphere maps of regional blood flow and regional ventilation

Preliminary results of a miniaturized respiratory sensor system used under hypergravity conditions up to 9gz

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Product

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Preliminary results of a miniaturized respiratory sensor system used under hypergravity conditions up to 9g_z