scholarly journals Steep head-down tilt has persisting effects on the distribution of pulmonary blood flow

2006 ◽  
Vol 101 (2) ◽  
pp. 583-589 ◽  
Author(s):  
A. Cortney Henderson ◽  
David L. Levin ◽  
Susan R. Hopkins ◽  
I. Mark Olfert ◽  
Richard B. Buxton ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Regional Blood Flow ◽  
Flow Distribution ◽  
Normal Subjects ◽  
Relative Dispersion ◽  
Lung Water ◽  
Before And After ◽  
Capillary Pressures ◽  
The Right

Head-down tilt has been shown to increase lung water content in animals and alter the distribution of ventilation in humans; however, its effects on the distribution of pulmonary blood flow in humans are unknown. We hypothesized that head-down tilt would increase the heterogeneity of pulmonary blood flow in humans, an effect analogous to the changes seen in the distribution of ventilation, by increasing capillary hydrostatic pressure and fluid efflux in the lung. To test this, we evaluated changes in the distribution of pulmonary blood flow in seven normal subjects before and after 1 h of 30° head-down tilt using the magnetic resonance imaging technique of arterial spin labeling. Data were acquired in triplicate before tilt and at 10-min intervals for 1 h after tilt. Pulmonary blood flow heterogeneity was quantified by the relative dispersion (standard deviation/mean) of signal intensity for all voxels within the right lung. Relative dispersion was significantly increased by 29% after tilt and remained elevated during the 1 h of measurements after tilt (0.84 ± 0.06 pretilt, 1.09 ± 0.09 calculated for all time points posttilt, P < 0.05). We speculate that the mechanism most likely responsible for our findings is that increased pulmonary capillary pressures and fluid efflux in the lung resulting from head-down tilt alters regional blood flow distribution.

Lung water is increased in regions of higher neutrophil retention after acute bead embolization

1996 ◽  
Vol 80 (5) ◽  
pp. 1513-1519 ◽  
Author(s):  
J. Tsang ◽  
B. Brush
Keyword(s):  
Blood Flow ◽  
Extravascular Lung Water ◽  
Right Atrium ◽  
Pulmonary Blood Flow ◽  
Regional Blood Flow ◽  
Lung Water ◽  
Microvascular Damage ◽  
Subsequent Formation ◽  
Permeability Pulmonary Edema ◽  
The Right

Previous reports have shown that neutrophils are retained in the lung after acute embolization and that these neutrophils play an important role in the subsequent formation of permeability pulmonary edema. The present study was designed to test the hypothesis that acute embolic injury results in microvascular damage in lung regions with the greater retention of neutrophils. Seventeen pigs (20 +/- 2 kg) were embolized by injecting polystyrene beads (250 microns; labeled with 131I) into the right atrium over 5 min. Five pigs, which received no embolic beads, served as controls. Neutrophils (89 +/- 5% pure), isolated on Ficoll-Histopaque gradient, were radiolabeled with 111In-oxine. Twenty minutes after embolization, the radiolabeled neutrophils were injected into the right atrium along with 85Sr-labeled microspheres to mark the initial neutrophil distribution within the lung as well as the regional pulmonary blood flow at the time of their delivery. The animals were killed 50 min after embolization, and the lungs were removed, frozen over liquid nitrogen, and cut into 60 samples. The data show that after embolization regional neutrophil retention was inversely related to the regional blood flow but was not affected by the embolic load in the same region. Regional extravascular lung water was increased in regions of higher neutrophil retention, but the regions with increased edema did not receive a greater embolic load. These results show that microvascular injury occurs in the lung regions with the greatest neutrophil retention and that this increased retention of neutrophils is unrelated to the extent of embolization.

Relationship between regional pulmonary edema and blood flow

1986 ◽  
Vol 60 (2) ◽  
pp. 449-457 ◽  
Author(s):  
J. Y. Tsang ◽  
E. M. Baile ◽  
J. C. Hogg
Keyword(s):  
Blood Flow ◽  
Pulmonary Edema ◽  
Pulmonary Blood Flow ◽  
Regional Blood Flow ◽  
Venous Blood ◽  
Regional Distribution ◽  
Blood Gases ◽  
Lung Water ◽  
Arteriovenous Shunts ◽  
Before And After

We studied the effect of edema on the regional distribution of pulmonary blood flow in 12 anesthetized dogs. Two were controls, six had low-pressure pulmonary edema, and four had high-pressure pulmonary edema. All were ventilated with 100% O2. The physiological shunt fraction (Qs/QT), as an indicator of the degree of venous admixture, was determined by measuring the arterial and venous blood gases and the hemoglobin at different times during the experiment. Cardiac output (QT) was modestly increased by opening the femoral arteriovenous shunts. The initial regional blood flow (Qi) and final regional blood flow (Qf) were marked before and after the shunts were opened, using two differently labeled macroaggregates. The dogs were then killed, and the lungs were removed and sampled completely so that Qi and Qf and the amount of regional extravascular lung water (Wdl) in each regional sample could be measured (sample size: wet wt = 5.9 +/- 2.9 g, n = 833; Wdl ranged from 5.15 +/- 1.18 to 14.42 +/- 2.34 g). The data show that QS/QT increased as QT increased in the three conditions studied. However, there was no correlation between Wdl and Qi, Qf, or the relative change in regional blood flow. The data also show that gravity affects regional blood flow more than it affects regional edema. We conclude that the increased Qs/QT seen with increased pulmonary blood flow cannot be explained by a preferential increase of blood flow to the more edematous regions.

Effect of regional pulmonary blood flow on extravascular lung water measurements with PET

1988 ◽  
Vol 65 (3) ◽  
pp. 1267-1273 ◽  
Author(s):  
M. Velazquez ◽  
D. P. Schuster
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Radiation Effects ◽  
External Source ◽  
Systematic Difference ◽  
Base Line ◽  
Lung Water ◽  
Positron Emission ◽  
Before And After ◽  
The Right

We examined the effect of regional pulmonary blood flow (PBF) on lung water measurements made with a blood-borne label (15O-water) and positron emission tomography (PET) in five dogs. The total lung water (TLW) content of a lung region obtained at equilibrium after intravenous injection of 15O-water (TLW-water) was compared with calculations made from lung density measurements (TLW-density) also obtained with PET. These latter measurements are proportional to the tissue attenuation of radioactivity originating from an external source encircling the animal and are independent of PBF. Comparisons were made before and 60 min after oleic acid-induced injury confined to the left caudal lobe (LCL). PBF fell 61% in regions from the dorsal half of the LCL after lung injury and was unchanged on the right side. Both before and after injury, TLW-density was 10-15% higher than TLW-water. This systematic difference is probably due to overestimates of TLW-density resulting from partial volume and scattered radiation effects. When TLW-water and TLW-density were compared in 151 3-ml regions from both normal and injured lung, the disparity between the two methods of calculating TLW increased in regions with a PBF less than 0.5 ml.min-1.ml lung-1 (less than 20% of base line). However, this represented only 22% of the injured regions analyzed. Thus lung water measurements made with PET and 15O-water are accurate until regional PBF is severely reduced. With PET, such areas can be eliminated from analysis or regions can be made sufficiently large so the overall effect on the TLW measurement is minimized.

Effects of pulmonary edema on regional pulmonary perfusion in the intact dog lung

1980 ◽  
Vol 49 (5) ◽  
pp. 834-840 ◽  
Author(s):  
A. B. Malik ◽  
H. van der Zee ◽  
P. H. Neumann ◽  
N. B. Gertzberg
Keyword(s):  
Blood Flow ◽  
Pulmonary Edema ◽  
Pulmonary Blood Flow ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Weight Ratio ◽  
Flow Distribution ◽  
Base Line ◽  
Dependent Lung ◽  
Lung Water ◽  
Pulmonary Hemodynamics

Regional pulmonary blood flow was determined in dogs during varying degrees of pulmonary edema induced by infusing 179.2-659.4 ml/kg normal saline over 2-3 h. Pulmonary hemodynamics and regional blood flows were measured during the base-line period and at 30 min postinfusion. The degree of pulmonary edema was determined by the final extravascular lung water-to-bloodless dry lung weight ratio (W/D). In dogs developing gross alveolar edema (W/D of 10.70 +/- 0.88 vs. 3.10 +/- 0.30 in controls), the blood flow was shifted to either upper or dependent lung regions. The shift to the upper regions was associated with an increased (P < 0.05) pulmonary arterial pressure (Ppa), whereas the shift to the dependent lung was not associated with a significant change in Ppa. Breathing 100% O2 did not prevent these shifts, suggesting that they were not due to localized hypoxic pulmonary vasoconstriction. The flow distribution patterns were also not related to regional differences in edema. In contrast to the changes during fulminant edema, blood flow distribution did not change after moderate levels of pulmonary edema (W/D of 6.03 0.69), suggesting that gross alveolar flooding is required for a redistribution of pulmonary blood flow. Flow redistribution to the upper lung during airway flooding may be due to increase in Ppa, whereas the increased flow in the dependent lung during the same degree of edema may be due to "bulging" of alveolar vessels into the air spaces, secondary to a decrease in surface activity.

Fractal properties of pulmonary blood flow: characterization of spatial heterogeneity

1990 ◽  
Vol 69 (2) ◽  
pp. 532-545 ◽  
Author(s):  
R. W. Glenny ◽  
H. T. Robertson
Keyword(s):  
Blood Flow ◽  
Spatial Heterogeneity ◽  
Pulmonary Blood Flow ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Fractal Model ◽  
Relative Dispersion ◽  
Flow Measurements ◽  
Residual Capacity ◽  
Blood Flow Measurements

The heterogeneity of pulmonary blood flow was examined using a fractal analytic procedure, and the results were compared with the traditional gravitational model of flow distribution. 99mTc-labeled macroaggregate was injected intravenously at functional residual capacity in six supine anesthetized dogs. The lungs were fixed in situ and sliced in transverse sections. The slices were imaged on a planar gamma camera, and a three-dimensional array of blood flow measurements was reconstructed for each lung. Fractal analysis was used to examine the spatial heterogeneity or RDs (relative dispersion = SD/mean) as a function of the number of pieces into which the flow array was subdivided. RDs was fractal and could be characterized by a fractal dimension (Ds) of 1.09 +/- 0.02, where a Ds of 1.0 reflects homogeneous flow and 1.5 indicates a random flow distribution. The data fit the fractal model exceptionally well with an average r = 0.98. RDs was examined in gravitational and isogravitational planes and as expected was greatest in the gravitational direction. However, the difference was small, suggesting that gravitation plays a secondary role to an underlying process producing heterogeneity. Within the limits of resolution attained by this study (piece volumes greater than 0.25 cm3), the heterogeneity of pulmonary blood flow is well characterized by a fractal model.

scholarly journals A novel diagnostic approach for assessing pulmonary blood flow distribution using conventional X-ray angiography

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0253565
Author(s):  
Takuya Sakaguchi ◽  
Yuichiro Watanabe ◽  
Masashi Hirose ◽  
Kohta Takei ◽  
Satoshi Yasukochi
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Pulmonary Angiography ◽  
Lung Perfusion ◽  
Blood Flow Distribution ◽  
Perfusion Scintigraphy ◽  
Lung Perfusion Scintigraphy ◽  
X Ray ◽  
The Right

Objective Quantitative assessment of pulmonary blood flow distribution is important when determining the clinical indications for treating pulmonary arterial branch stenosis. Lung perfusion scintigraphy is currently the gold standard for quantitative blood flow measurement. However, it is expensive, cannot provide a real-time assessment, requires additional sedation, and exposes the patient to ionizing radiation. The aim of this study was to investigate the feasibility of a novel technology for measuring pulmonary blood flow distribution in each lung by conventional X-ray pulmonary angiography and to compare its performance to that of lung perfusion scintigraphy. Methods Contrast-enhanced X-ray pulmonary angiography images were acquired at a frame rate of 30 frames per second. The baseline mask image, obtained before contrast agent injection, was subtracted from subsequent, consecutive images. The time-signal intensity curves of two regions of interest, established at each lung field, were obtained on a frame-to-frame basis. The net increase in signal intensity within each region at the torrent period during the second cardiac cycle before contrast agent enhancement over the total lung field was measured, and the right-to-left ratio of the signal intensity was calculated. The right-to-left ratio obtained with this approach was compared to that obtained with scintigraphy. Agreement of the right-to-left ratio between X-ray angiography and lung scintigraphy measurements was assessed using linear fitting with the Pearson correlation coefficient. Result The calculation of the right-to-left ratio of pulmonary blood flow by our kinetic model was feasible for seven children as a pilot study. The right-to-left ratio of pulmonary blood flow distribution calculated from pulmonary angiography was in good agreement with that of lung perfusion scintigraphy, with a Pearson correlation coefficient of 0.91 and a slope of linear fit of 1.2 (p<0.005). Conclusion The novel diagnostic technology using X-ray pulmonary angiography from our kinetic model can feasibly quantify the right-to-left ratio of pulmonary blood flow distribution. This technology may serve as a substitute for lung perfusion scintigraphy, which is quite beneficial for small children susceptible to radiation exposure.

Redistribution of pulmonary blood flow during unilateral hypoxia in prone and supine dogs

1998 ◽  
Vol 84 (6) ◽  
pp. 2010-2019 ◽  
Author(s):  
Christopher M. Mann ◽  
Karen B. Domino ◽  
Sten M. Walther ◽  
Robb W. Glenny ◽  
Nayak L. Polissar ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Regional Distribution ◽  
Left Lung ◽  
Flow Distribution ◽  
Random Order ◽  
Total Flow ◽  
Hypoxic Vasoconstriction ◽  
Anesthetized Dogs ◽  
The Right

We used fluorescent-labeled microspheres in pentobarbital-anesthetized dogs to study the effects of unilateral alveolar hypoxia on the pulmonary blood flow distribution. The left lung was ventilated with inspired O2 fraction of 1.0, 0.09, or 0.03 in random order; the right lung was ventilated with inspired O2 fraction of 1.0. The lungs were removed, cleared of blood, dried at total lung capacity, then cubed to obtain ∼1,500 small pieces of lung (∼1.7 cm3). The coefficient of variation of flow increased ( P < 0.001) in the hypoxic lung but was unchanged in the hyperoxic lung. Most (70–80%) variance in flow in the hyperoxic lung was attributable to structure, in contrast to only 30–40% of the variance in flow in the hypoxic lung ( P < 0.001). When adjusted for the change in total flow to each lung, 90–95% of the variance in the hyperoxic lung was attributable to structure compared with 70–80% in the hypoxic lung ( P < 0.001). The hilar-to-peripheral gradient, adjusted for change in total flow, decreased in the hypoxic lung ( P = 0.005) but did not change in the hyperoxic lung. We conclude that hypoxic vasoconstriction alters the regional distribution of flow in the hypoxic, but not in the hyperoxic, lung.

Effects of pulmonary blood flow on the fractal nature of flow heterogeneity in sheep lungs

1994 ◽  
Vol 77 (3) ◽  
pp. 1474-1479 ◽  
Author(s):  
S. D. Caruthers ◽  
T. R. Harris
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Random Order ◽  
Portion Size ◽  
Relative Dispersion ◽  
Fractal Nature ◽  
Total Flow ◽  
Blood Flows

The spatial heterogeneity of pulmonary blood flow can be described by the relative dispersion (RD) of weight-flow histograms (RD = SD/mean). Glenny and Robertson (J. Appl. Physiol. 69: 532–545, 1990) showed that RD of flow in the lung is fractal in nature, characterized by the fractal dimension (D) and RD for the smallest realizable volume element (RDref). We studied the effects of increasing total pulmonary blood flow on D and RDref. In eight in situ perfused sheep lung preparations, 15-microns radio-labeled microspheres were injected into the pulmonary artery at five different blood flows ranging, in random order, from 1.5 to 5.0 l/m. The lungs were in zone 2 at the lower flows and in zone 3 at the higher flows. The lungs were removed, dried, cut into 2 x 2 x 2-cm3 pieces, weighed, and then counted for microsphere radioactivity. Fractal plots of log(weight) vs. log(RD) were constructed by iteratively combining neighboring pieces and then calculating RD with the increasingly larger portion size. D, which is one minus the slope of the fit through this plot, was 1.14 +/- 0.09 and did not change as blood flow increased. However, RDref decreased significantly (P < 0.01) as total flow increased. We conclude that the fractal nature of pulmonary blood flow distribution is not altered by changes in overall flow.

scholarly journals Assessing potential errors of MRI-based measurements of pulmonary blood flow using a detailed network flow model

2012 ◽  
Vol 113 (1) ◽  
pp. 130-141 ◽  
Author(s):  
K. S. Burrowes ◽  
R. B. Buxton ◽  
G. K. Prisk
Keyword(s):  
Blood Flow ◽  
Network Flow ◽  
Pulmonary Blood Flow ◽  
Sagittal Plane ◽  
Flow Distribution ◽  
Image Plane ◽  
Relative Dispersion ◽  
Plane Flow ◽  
Image Planes ◽  
Imaging Plane

MRI images of pulmonary blood flow using arterial spin labeling (ASL) measure the delivery of magnetically tagged blood to an image plane during one systolic ejection period. However, the method potentially suffers from two problems, each of which may depend on the imaging plane location: 1) the inversion plane is thicker than the imaging plane, resulting in a gap that blood must cross to be detected in the image; and 2) ASL includes signal contributions from tagged blood in conduit vessels (arterial and venous). By using an in silico model of the pulmonary circulation we found the gap reduced the ASL signal to 64–74% of that in the absence of a gap in the sagittal plane and 53–84% in the coronal. The contribution of the conduit vessels varied markedly as a function of image plane ranging from ∼90% of the overall signal in image planes that encompass the central hilar vessels to <20% in peripheral image planes. A threshold cutoff removing voxels with intensities >35% of maximum reduced the conduit vessel contribution to the total ASL signal to ∼20% on average; however, planes with large contributions from conduit vessels underestimate acinar flow due to a high proportion of in-plane flow, making ASL measurements of perfusion impractical. In other image planes, perfusion dominated the resulting ASL images with good agreement between ASL and acinar flow. Similarly, heterogeneity of the ASL signal as measured by relative dispersion is a reliable measure of heterogeneity of the acinar flow distribution in the same image planes.

Pulmonary blood flow distribution after lobar oleic acid injury: a PET study

1988 ◽  
Vol 65 (5) ◽  
pp. 2228-2235 ◽  
Author(s):  
M. Velazquez ◽  
D. P. Schuster
Keyword(s):  
Blood Flow ◽  
Oleic Acid ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Control Group ◽  
Base Line ◽  
Lung Water ◽  
Positron Emission ◽  
Blood Flow Reduction ◽  
Pulmonary Arterial Catheter

We evaluated the importance of hypoxic vasoconstriction as a mechanism for pulmonary blood flow reduction during unilobar oleic acid lung injury in dogs. Pulmonary blood flow (PBF) and lung water were measured with positron emission tomography. Data from the injured left (LCL) and right (RCL) caudal lobes were compared in 23 dogs. Six dogs were used to demonstrate that endotoxin (15 micrograms/kg) prevents changes in regional PBF during selective hypoxic ventilation of the LCL. In 17 dogs, oleic acid (OA, 0.015 ml/kg) was injected into the LCL through a balloon-wedged pulmonary arterial catheter. Five dogs received OA only (control group), eight received endotoxin (15 mcg/kg) before OA was administered (endotoxin group), and four were treated with prostaglandin E1 (PGE1) after OA (PGE1 group). The base-line left-to-right PBF ratio (LCL/RCL PBF) was 1.01 +/- 0.11 (SD) for the control group and 1.07 +/- 0.16 for the PGE1 group. One minute after OA, LCL/RCL PBF feel significantly (0.32 +/- 0.15 and 0.32 +/- 0.13 for the control and PGE1 groups, respectively) before any significant increase in lung water was detected. In all 17 dogs that received OA, the LCL/RCL PBF remained severely reduced 60 min after OA compared with base-line values (0.41 +/- 0.15, 0.49 +/- 0.06, and 0.26 +/- 0.13 for the control, PGF1, and endotoxin groups, respectively) despite treatment with endotoxin or PGE1. Lung water measurements obtained 60 min after OA increased significantly (P less than 0.05) in the injured lobe (LCL) but not in the normal lobe (RCL) in all dog groups, whereas PBF to the LCL remained significantly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

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