Supine, prone, right and left gravitational effects on human pulmonary circulation

Abstract Background Body position can be optimized for pulmonary ventilation/perfusion matching during surgery and intensive care. However, positional effects upon distribution of pulmonary blood flow and vascular distensibility measured as the pulmonary blood volume variation have not been quantitatively characterized. In order to explore the potential clinical utility of body position as a modulator of pulmonary hemodynamics, we aimed to characterize gravitational effects upon distribution of pulmonary blood flow, pulmonary vascular distension, and pulmonary vascular distensibility. Methods Healthy subjects (n = 10) underwent phase contrast cardiovascular magnetic resonance (CMR) pulmonary artery and vein flow measurements in the supine, prone, and right/left lateral decubitus positions. For each lung, blood volume variation was calculated by subtracting venous from arterial flow per time frame. Results Body position did not change cardiac output (p = 0.84). There was no difference in blood flow between the superior and inferior pulmonary veins in the supine (p = 0.92) or prone body positions (p = 0.43). Compared to supine, pulmonary blood flow increased to the dependent lung in the lateral positions (16–33%, p = 0.002 for both). Venous but not arterial cross-sectional vessel area increased in both lungs when dependent compared to when non-dependent in the lateral positions (22–27%, p ≤ 0.01 for both). In contrast, compared to supine, distensibility increased in the non-dependent lung in the lateral positions (68–113%, p = 0.002 for both). Conclusions CMR demonstrates that in the lateral position, there is a shift in blood flow distribution, and venous but not arterial blood volume, from the non-dependent to the dependent lung. The non-dependent lung has a sizable pulmonary vascular distensibility reserve, possibly related to left atrial pressure. These results support the physiological basis for positioning patients with unilateral pulmonary pathology with the “good lung down” in the context of intensive care. Future studies are warranted to evaluate the diagnostic potential of these physiological insights into pulmonary hemodynamics, particularly in the context of non-invasively characterizing pulmonary hypertension.

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

Journal of Applied Physiology ◽

10.1152/jappl.1980.49.5.834 ◽

1980 ◽

Vol 49 (5) ◽

pp. 834-840 ◽

Cited By ~ 7

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.

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EFFECT OF THE PATENT DUCTUS ARTERIOSUS ON THE PULMONARY BLOOD FLOW, BLOOD VOLUME, HEART RATE, BLOOD PRESSURE, ARTERIAL BLOOD GASES AND pH

PEDIATRICS ◽

10.1542/peds.6.4.557 ◽

1950 ◽

Vol 6 (4) ◽

pp. 557-572

Author(s):

DONALD E. CASSELS ◽

MINERVA MORSE ◽

W. E. ADAMS

Keyword(s):

Heart Rate ◽

Blood Flow ◽

Patent Ductus Arteriosus ◽

Blood Volume ◽

Pulmonary Blood Flow ◽

Ductus Arteriosus ◽

Blood Gases ◽

Arterial Blood Gases ◽

Arterial Blood ◽

Patent Ductus

The effect of the patent ductus arteriosus on the circulation and on the arterial blood gases and pHs has been studied. The pulmonary blood flow diminished 19.6 to 61.8% following ligation in 12 cases examined. The blood volume diminished following closure of the ductus in most cases. Likewise, the heart rate lessened and the pulse pressure was lower after surgery. Arterial oxygen saturation was low preoperatively in some cases and in most instances postoperatively, and this low value sometimes persisted. Some aspects of the data presented have been discussed in detail.

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Pulmonary fluid balance following pulmocutaneous baroreceptor denervation in the toad

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.1.331 ◽

1986 ◽

Vol 61 (1) ◽

pp. 331-337 ◽

Cited By ~ 10

Author(s):

A. W. Smits ◽

N. H. West ◽

W. W. Burggren

Keyword(s):

Blood Flow ◽

Pulmonary Blood Flow ◽

Venous Pressure ◽

Driving Pressure ◽

Pulmonary Hemodynamics ◽

Pulmonary Capillaries ◽

Neural Input ◽

Order Of Magnitude ◽

Capillary Resistance ◽

Recurrent Laryngeal Nerves

Pulmonary hemodynamics and net transcapillary fluid flux (NTFF) were measured in conscious toads before and following bilateral denervation of the recurrent laryngeal nerves (rLN), which contain afferents from baroreceptors located in the pulmocutaneous arteries. Denervation caused an acute doubling of the arterial-venous pressure gradient across the lung and a threefold increase in pulmonary blood flow. Calculated pulmonary vascular resistance fell and remained below control values through the period of experimentation. NTFF increased by an order of magnitude (0.74–7.77 ml X kg-1 X min-1), as filtration increased in response to the hemodynamic changes caused by rLN denervation. There was a better correlation between NTFF and pulmonary blood flow than between NTFF and pulmonary driving pressure. Our results support the view that tonic neural input from pulmocutaneous baroreceptors protects the anuran lung from edema by restraining pulmonary driving pressure and blood flow and perhaps by reflexly maintaining vascular tone in the extrinsic pulmonary artery, therefore tending to increase the pre-to-postpulmonary capillary resistance ratio and biasing the Starling relationship in the pulmonary capillaries against filtration.

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Modification of bronchial blood flow during allergic airway responses

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.1.272 ◽

1988 ◽

Vol 65 (1) ◽

pp. 272-282 ◽

Cited By ~ 14

Author(s):

W. M. Long ◽

L. D. Yerger ◽

H. Martinez ◽

E. Codias ◽

C. L. Sprung ◽

...

Keyword(s):

Blood Flow ◽

Specific Antigen ◽

Mast Cell Degranulation ◽

Arterial Blood Flow ◽

Antigen Challenge ◽

Vascular Response ◽

Pulmonary Hemodynamics ◽

Arterial Blood ◽

Airway Responses ◽

Induced Changes

Ascaris suum antigen effects on mean airflow resistance (RL) and bronchial arterial blood flow (Qbr) were studied in allergic anesthetized sheep with documented airway responses. Qbr was measured with electromagnetic flow probes, and supplemental O2 prevented antigen-induced hypoxemia. Aerosol challenge with this specific antigen increased RL and Qbr significantly. Cromolyn sodium aerosol pretreatment prevented antigen-induced increases in RL but not in Qbr. Intravenous cromolyn, however, prevented increases in Qbr and RL, suggesting a role for mast cell degranulation in both bronchomotor and bronchovascular responses to antigen. Antigen-induced increases in Qbr were not solely attributable to histamine release. Indomethacin pretreatment attenuated the antigen-induced increase in Qbr, thus suggesting that vasodilator cyclooxygenase products contribute to the vascular response. Antigen challenge significantly decreased Qbr after indomethacin and metiamide pretreatment, which suggests that vasoconstrictor substances released after antigen exposure also modulate Qbr; however, released vasodilators overshadow vasoconstrictor effects. Thus antigen challenge affects Qbr by locally releasing histamine and vasodilator prostaglandins as well as vasoconstrictor substances. These effects were independent of antigen-induced changes in systemic and pulmonary hemodynamics.

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Effect of Pulmonary Blood Flow on Lung Water and Pulmonary Hemodynamics in the Canine Lung Lobe

European Surgical Research ◽

10.1159/000129094 ◽

1990 ◽

Vol 22 (3) ◽

pp. 136-142 ◽

Cited By ~ 3

Author(s):

K. Nakahara ◽

S. Nanjo ◽

A. Matsumura ◽

Y. Kawashima

Keyword(s):

Blood Flow ◽

Pulmonary Blood Flow ◽

Lung Water ◽

Pulmonary Hemodynamics ◽

Lung Lobe

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Bidirectional Ductal Shunting and Preductal to Postductal Oxygenation Gradient in Persistent Pulmonary Hypertension of the Newborn

Children ◽

10.3390/children7090137 ◽

2020 ◽

Vol 7 (9) ◽

pp. 137

Author(s):

Amy Lesneski ◽

Morgan Hardie ◽

William Ferrier ◽

Satyan Lakshminrusimha ◽

Payam Vali

Keyword(s):

Blood Flow ◽

Pulmonary Hypertension ◽

Pulmonary Blood Flow ◽

Ductus Arteriosus ◽

Arterial Oxygen Tension ◽

Persistent Pulmonary Hypertension ◽

Arterial Oxygen ◽

Meconium Aspiration ◽

Arterial Blood Gas ◽

Arterial Blood

Background: The aim was to evaluate the relationship between the direction of the patent ductus arteriosus (PDA) shunt and the pre- and postductal gradient for arterial blood gas (ABG) parameters in a lamb model of meconium aspiration syndrome (MAS) with persistent pulmonary hypertension of the newborn (PPHN). Methods: PPHN was induced by intermittent umbilical cord occlusion and the aspiration of meconium through the tracheal tube. After delivery, 13 lambs were ventilated and simultaneous 129 pairs of pre- and postductal ABG were drawn (right carotid and umbilical artery, respectively) while recording the PDA and the carotid and pulmonary blood flow. Results: Meconium aspiration resulted in hypoxemia. The bidirectional ductal shunt had a lower postductal partial arterial oxygen tension ([PaO2] with lower PaO2/FiO2 ratio—97 ± 36 vs. 130 ± 65 mmHg) and left pulmonary flow (81 ± 52 vs. 133 ± 82 mL/kg/min). However, 56% of the samples with a bidirectional shunt had a pre- and postductal saturation gradient of < 3%. Conclusions: The presence of a bidirectional ductal shunt is associated with hypoxemia and low pulmonary blood flow. The absence of a pre- and postductal saturation difference is frequently observed with bidirectional right-to-left shunting through the PDA, and does not exclude a diagnosis of PPHN in this model.

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Splenectomy impairs diffusive oxygen transport in the lung of dogs

Journal of Applied Physiology ◽

10.1152/japplphysiol.01600.2005 ◽

2006 ◽

Vol 101 (1) ◽

pp. 289-297 ◽

Cited By ~ 15

Author(s):

D. Merrill Dane ◽

Connie C. W. Hsia ◽

Eugene Y. Wu ◽

Richard T. Hogg ◽

Deborah C. Hogg ◽

...

Keyword(s):

Blood Flow ◽

Blood Volume ◽

Pulmonary Blood Flow ◽

Compensatory Mechanism ◽

Diffusing Capacity ◽

Restrictive Lung Disease ◽

Before And After ◽

Capillary Blood Volume ◽

Exercise Induced ◽

Experimental Findings

The spleen acts as an erythrocyte reservoir in highly aerobic species such as the dog and horse. Sympathetic-mediated splenic contraction during exercise reversibly enhances convective O2 transport by increasing hematocrit, blood volume, and O2-carrying capacity. Based on theoretical interactions between erythrocytes and capillary membrane (Hsia CCW, Johnson RL Jr, and Shah D. J Appl Physiol 86: 1460–1467, 1999) and experimental findings in horses of a postsplenectomy reduction in peripheral O2-diffusing capacity (Wagner PD, Erickson BK, Kubo K, Hiraga A, Kai M, Yamaya Y, Richardson R, and Seaman J. Equine Vet J 18, Suppl: 82–89, 1995), we hypothesized that splenic contraction also augments diffusive O2 transport in the lung. Therefore, we have measured lung diffusing capacity (DlCO) and its components during exercise by a rebreathing technique in six adult foxhounds before and after splenectomy. Splenectomy eliminated exercise-induced polycythemia, associated with a 30% reduction in maximal O2 uptake. At any given pulmonary blood flow, DlCO was significantly lower after splenectomy owing to a lower membrane diffusing capacity, whereas pulmonary capillary blood volume changed variably; microvascular recruitment, indicated by the slope of the increase in DlCO with respect to pulmonary blood flow, was also reduced. We conclude that splenic contraction enhances both convective and diffusive O2 transport and provides another compensatory mechanism for maintaining alveolar O2 transport in the presence of restrictive lung disease or ambient hypoxia.

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Cardiovascular effects of acute hemorrhage in fetal lambs

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1981.240.1.h45 ◽

1981 ◽

Vol 240 (1) ◽

pp. H45-H48 ◽

Cited By ~ 3

Author(s):

P. L. Toubas ◽

N. H. Silverman ◽

M. A. Heymann ◽

A. M. Rudolph

Keyword(s):

Heart Rate ◽

Blood Flow ◽

Blood Volume ◽

Age Groups ◽

Blood Gases ◽

Cardiovascular Effects ◽

Carbon Dioxide Tension ◽

Acute Hemorrhage ◽

Arterial Blood ◽

Placental Blood

The effects of acute hemorrhage were studied in two groups each with six fetal lambs (100-116 amd 128-147 days gestation) 3-4 days after we implanted catheters. Fetal blood pressures, heart rate, arterial blood gases and pH, and combined ventricular output and its distribution (radionuclide-labeled microsphere technique) were measured before and 5 min after removal of 15% of fetal-placental blood volume measured by 125I-albumin dilution. Because there were no differences in responses in the two age groups, the data were pooled. Fetal arterial mean pressure fell significantly (50.7 +/- 2.5 to 45.5 +/- 2.6 mmHg) as did heart rate (186 +/- 6 to 151 +/- 13 beats/min) and arterial blood pH (7.39 +/- 0.02 to 7.30 +/- 0.02); arterial blood carbon dioxide tension rose (39.7 +/- 29 to 44.1 +/- 4.4). Combined ventricular output fell from 610 +/- 58 to 448 +/- 45 ml . kg-1 . min-1 (P < 0.05). Blood flow to the umbilical-placental circulation, as well as to the fetal body, fell significantly. Blood flow to the kidneys, gastrointestinal tracts, and lungs also fell, but flow to other organs was maintained. Blood volume reduction in the fetus markedly influences blood gas exchange, because it results in a reduction of umbilical-placental blood flow associated with the fall in arterial pressure.

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Vertical gradients in regional lung density and perfusion in the supine human lung: the Slinky effect

Journal of Applied Physiology ◽

10.1152/japplphysiol.01289.2006 ◽

2007 ◽

Vol 103 (1) ◽

pp. 240-248 ◽

Cited By ~ 134

Author(s):

Susan R. Hopkins ◽

A. Cortney Henderson ◽

David L. Levin ◽

Kei Yamada ◽

Tatsuya Arai ◽

...

Keyword(s):

Blood Flow ◽

Pulmonary Blood Flow ◽

Breath Holding ◽

Proton Density ◽

Dependent Lung ◽

Lung Density ◽

Regional Lung ◽

Vertical Height ◽

Vertical Gradients

In vivo radioactive tracer and microsphere studies have differing conclusions as to the magnitude of the gravitational effect on the distribution of pulmonary blood flow. We hypothesized that some of the apparent vertical perfusion gradient in vivo is due to compression of dependent lung increasing local lung density and therefore perfusion/volume. To test this, six normal subjects underwent functional magnetic resonance imaging with arterial spin labeling during breath holding at functional residual capacity, and perfusion quantified in nonoverlapping 15 mm sagittal slices covering most of the right lung. Lung proton density was measured in the same slices using a short echo 2D-Fast Low-Angle SHot (FLASH) sequence. Mean perfusion was 1.7 ± 0.6 ml·min−1·cm−3 and was related to vertical height above the dependent lung (slope = −3%/cm, P < 0.0001). Lung density averaged 0.34 ± 0.08 g/cm3 and was also related to vertical height (slope = −4.9%/cm, P < 0.0001). By contrast, when perfusion was normalized for regional lung density, the slope of the height-perfusion relationship was not significantly different from zero ( P = 0.2). This suggests that in vivo variations in regional lung density affect the interpretation of vertical gradients in pulmonary blood flow and is consistent with a simple conceptual model: the lung behaves like a Slinky (Slinky is a registered trademark of Poof-Slinky Incorporated), a deformable spring distorting under its own weight. The greater density of lung tissue in the dependent regions of the lung is analogous to a greater number of coils in the dependent portion of the vertically oriented spring. This implies that measurements of perfusion in vivo will be influenced by density distributions and will differ from excised lungs where density gradients are reduced by processing.

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