Effect of blood flow rate and blood flow history on newborn pulmonary microcirculation

1991 ◽  
Vol 261 (2) ◽  
pp. H271-H279 ◽  
Author(s):  
C. D. Fike ◽  
M. R. Kaplowitz
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Left Atrial ◽  
Total Pressure ◽  
Pulmonary Blood Flow ◽  
Blood Flow Rate ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Flow Rates ◽  
Pulmonary Arterial

The purpose of this study was to determine whether increased pulmonary blood flow and/or the history of pulmonary blood flow alters microvascular pressures in lungs of newborns. Using the direct micropuncture technique, we measured pressures in 20- to 60-microns-diameter arterioles and venules in isolated lungs of newborn rabbits at consecutive blood flow rates of 50 (baseline), 100, and/or 200 ml.min-1.kg-1. Then in some lungs we returned blood flow rate to baseline and repeated microvascular pressure measurements. We kept left atrial pressure the same at all blood flow rates. When blood flow rate increased and left atrial pressure was maintained constant, pulmonary arterial, 20- to 60-microns-diameter arteriolar, and 20- to 60-microns-diameter venular pressures increased such that the percentage of total pressure drop that occurred across veins increased. When we returned blood flow to baseline, venular pressure returned to baseline, but arteriolar and pulmonary arterial pressures returned to values less than baseline so that the percentage of the total pressure drop that occurred across microvessels decreased. Thus both blood flow rate and blood flow history are important determinants of the longitudinal distribution of pulmonary vascular pressures across newborn lungs. These findings also suggest that in newborn lungs venules greater than 60 microns diameter are poorly distensible such that higher blood flow rates result in increased microvascular pressures. Hence, under conditions of increased pulmonary blood flow, such as occurs with left to right shunts, the tendency for edema formation will increase in newborn lungs even if left atrial pressure does not increase.

Longitudinal distribution of pulmonary vascular resistance with very high pulmonary blood flow

1987 ◽  
Vol 62 (1) ◽  
pp. 344-358 ◽  
Author(s):  
M. Younes ◽  
Z. Bshouty ◽  
J. Ali
Keyword(s):  
Blood Flow ◽  
Weight Gain ◽  
Left Atrial ◽  
Pulmonary Blood Flow ◽  
Lower Lobe ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Longitudinal Distribution ◽  
Flow Rates ◽  
Flow Threshold

Dog left upper lobes (LUL) were perfused in situ via the left lower lobe artery. Lobe weight was continuously monitored. Increasing lobar flow from normal to 10 times normal had little effect on left atrial pressure, which ranged from 1 to 5 mmHg. There was a flow threshold (Qth) below which lobar weight was stable. Qth ranged from 1.1 to 1.55 l/min (mean 1.27) corresponding to four times normal LUL blood flow. Above Qth, step increases in lobar flow resulted in progressive weight gain at a constant rate that was proportional to flow. The effective pressure at the filtration site (EFP) at different flow rates was estimated from the static vascular pressure that resulted in the same rate of weight gain. From this value and from mean pulmonary arterial (PA) and left atrial (LA) pressures, we calculated resistance upstream (Rus) and downstream (Rds) from filtration site. At Qth, Rds accounted for 60% of total resistance. This fraction increased progressively with flow, reaching 83% at Q of 10 times normal. We conclude that during high pulmonary blood flow EFP is closer to PA pressure than it is to LA pressure, and that this becomes progressively more so as a function of flow. As a result, the lung accumulates water at flow rates in excess of four times normal despite a normal left atrial pressure.

Lymph flow during increases in pulmonary blood flow and microvascular pressure in dogs

1988 ◽  
Vol 255 (5) ◽  
pp. H1149-H1155 ◽  
Author(s):  
F. A. Grimbert ◽  
D. Martin ◽  
J. C. Parker ◽  
A. E. Taylor
Keyword(s):  
Blood Flow ◽  
Left Atrial ◽  
Pulmonary Blood Flow ◽  
Protein Concentration ◽  
Balloon Catheter ◽  
Arterial Occlusion ◽  
Lymph Flow ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
The Relationship

We studied the effects of an increase in pulmonary blood flow (PBF) on steady-state lung lymph flow (QL) and protein transport in anesthetized dogs (n = 7) to estimate the effect of vascular recruitment in zone 3 on transvascular filtration. At the end of each experiment, we increased left atrial pressure to 25-30 mmHg using a balloon catheter and obtained a washdown of the lymph protein concentration. PBF was increased with an extracorporeal circuit, which pumped blood from the left to the right atrium, and increases in pulmonary capillary pressure (Pc) were minimized by lowering left atrial pressure. PBF was measured by thermodilution, and Pc was measured by transient analysis of arterial occlusion pressure with a Swan-Ganz catheter. PBF increases averaged 78% with increases ranging from 36 to 118%. Pc increases ranged from 0.5 to 6.3 mmHg, and QL increases averaged 31% with changes ranging from -2 to +138%. We observed a 16% increase in QL for each 1-mmHg increase in Pc during increased PBF, which was comparable to the relationship previously observed after an increased left atrial pressure. Lymph-to-plasma total protein concentration ratios (CL/CP) decreased from 0.71 +/- 0.04 to 0.625 +/- 0.06 during increased PBF. The relationship between CL/CP, QL, and Pc for both increased blood flow and increased left atrial pressure were within the expected range for increased pressure alone. These data suggest that there was minimal vascular recruitment for transvascular filtration in zone 3 when pulmonary blood flow was increased. Microvascular filtration pressure was the main determinant of fluid and protein transvascular filtration under these conditions.

The Effect of Hematocrit on the Clearance of Small Molecules during Hemodialysis

1983 ◽  
Vol 6 (3) ◽  
pp. 127-130 ◽  
Author(s):  
C. Woffindin ◽  
N.A. Hoenich ◽  
D.N.S. Kerr
Keyword(s):  
Blood Flow ◽  
Regression Analysis ◽  
Small Molecules ◽  
Flat Plate ◽  
Flow Rate ◽  
Distribution Curve ◽  
Blood Flow Rate ◽  
Hollow Fibre ◽  
Urea Clearance ◽  
Flow Rates

Data collected during the evaluation of a series of hemodialysers were analysed to see the effect of hematocrit on the clearance of urea and creatinine. All evaluations were performed on patients with a range of hematocrits with a mean close to 20%. The urea clearance of those in the upper half of the distribution curve (mean hematocrit 29.4%) was not significantly different from that of patients in the lower half of the distribution curve (mean hematocrit 16.9%) whether the clearance was studied at high or low blood flow rates and with hollow fibre or flat plate disposable hemodialysers. Likewise, there was no correlation between hematocrit and urea clearance by regression analysis. In contrast, the clearance of creatinine was affected by hematocrit being greater at lower hematocrit values. This difference was independent of blood flow rate and dialyser type and was confirmed by regression analysis.

scholarly journals In vivo / in vitro Correlation of Pharmacokinetics of Gentamicin, Vancomycin, Teicoplanin and Doripenem in a Bovine Blood Hemodialysis Model

2021 ◽  
Vol 12 ◽  
Author(s):  
M G Vossen ◽  
S Pferschy ◽  
C Milacek ◽  
M Haidinger ◽  
Mario Karolyi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Renal Replacement Therapy ◽  
Protein Binding ◽  
Replacement Therapy ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Bovine Blood ◽  
Flow Rates ◽  
Dialysate Flow Rate

Background: Elimination of a drug during renal replacement therapy is not only dependent on flow rates, molecular size and protein binding, but is often influenced by difficult to predict drug membrane interactions. In vitro models allow for extensive profiling of drug clearance using a wide array of hemofilters and flow rates. We present a bovine blood based in vitro pharmacokinetic model for intermittent renal replacement therapy.Methods: Four different drugs were analyzed: gentamicin, doripenem, vancomicin and teicoplanin. The investigated drug was added to a bovine blood reservoir connected to a hemodialysis circuit. In total seven hemofilter models were analyzed using commonly employed flow rates. Pre-filter, post-filter and dialysate samples were drawn, plasmaseparated and analyzed using turbidimetric assays or HPLC. Protein binding of doripenem and vancomycin was measured in bovine plasma and compared to previously published values for human plasma.Results: Clearance values were heavily impacted by choice of membrane material and surface as well as by dialysis parameters such as blood flow rate. Gentamicin clearance ranged from a minimum of 90.12 ml/min in a Baxter CAHP-170 diacetate hemofilter up to a maximum of 187.90 ml/min in a Fresenius medical company Fx80 polysulfone model (blood flow rate 400 ml/min, dialysate flow rate 800 ml/min). Clearance of Gentamicin vs Vancomicin over the F80s hemofilter model using the same flow rates was 137.62 mL vs 103.25 ml/min. Doripenem clearance with the Fx80 was 141.25 ml/min.Conclusion: Clearance values corresponded very well to previously published data from clinical pharmacokinetic trials. In conjunction with in silico pharmacometric models. This model will allow precise dosing recommendations without the need of large scale clinical trials.

Effect of thoracic duct drainage on hydrostatic pulmonary edema and pleural effusion in sheep

1991 ◽  
Vol 71 (1) ◽  
pp. 314-316 ◽  
Author(s):  
S. J. Allen ◽  
R. E. Drake ◽  
G. A. Laine ◽  
J. C. Gabel
Keyword(s):  
Pleural Effusion ◽  
Central Venous Pressure ◽  
Pulmonary Edema ◽  
Thoracic Duct ◽  
Left Atrial ◽  
Venous Pressure ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Central Venous ◽  
Pulmonary Arterial

Positive end-expiratory pressure (PEEP) increases central venous pressure, which in turn impedes return of systemic and pulmonary lymph, thereby favoring formation of pulmonary edema with increased microvascular pressure. In these experiments we examined the effect of thoracic duct drainage on pulmonary edema and hydrothorax associated with PEEP and increased left atrial pressure in unanesthetized sheep. The sheep were connected via a tracheostomy to a ventilator that supplied 20 Torr PEEP. By inflation of a previously inserted intracardiac balloon, left atrial pressure was increased to 35 mmHg for 3 h. Pulmonary arterial, systemic arterial, and central venous pressure as well as thoracic duct lymph flow rate were continuously monitored, and the findings were compared with those in sheep without thoracic duct cannulation (controls). At the end of the experiment we determined the severity of pulmonary edema and the volume of pleural effusion. With PEEP and left atrial balloon insufflation, central venous and pulmonary arterial pressure were increased approximately threefold (P less than 0.05). In sheep with a thoracic duct fistula, pulmonary edema was less (extra-vascular fluid-to-blood-free dry weight ratio 4.8 +/- 1.0 vs. 6.1 +/- 1.0; P less than 0.05), and the volume of pleural effusion was reduced (2.0 +/- 2.9 vs. 11.3 +/- 9.6 ml; P less than 0.05). Our data signify that, in the presence of increased pulmonary microvascular pressure and PEEP, thoracic duct drainage reduces pulmonary edema and hydrothorax.

Effects of left atrial pressure on the pulmonary vascular response to hypoxic ventilation

1991 ◽  
Vol 70 (5) ◽  
pp. 1991-1995 ◽  
Author(s):  
S. A. Gu ◽  
J. Ducas ◽  
U. Schick ◽  
R. M. Prewitt
Keyword(s):  
Arterial Pressure ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Mean Value ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Vascular Response ◽  
Wide Range ◽  
Pulmonary Arterial ◽  
The Mean

We investigated the effects of hypoxic ventilation on the pulmonary arterial pressure- (P) flow (Q) relationship in an intact canine preparation. Mean pulmonary P-Q coordinates were obtained during hypoxic ventilation and during ventilation with 100% O2 at normal and at increased left atrial pressure. Specifically, we tested the hypothesis that, over a wide range, changes in left atrial pressure would alter the effects of hypoxic ventilation on pulmonary P-Q characteristics. Seven dogs were studied. When left atrial pressure was normal (5 mmHg), the mean value of the extrapolated intercept (PI) of the linear P-Q relationship was 10.9 mmHg and the slope (incremental vascular resistance, IR) of the P-Q relationship was 2.2 mmHg.l-1.min. Hypoxic ventilation increased PI to 18 mmHg (P less than 0.01) but did not affect IR. Subsequently, during ventilation with 100% O2, when left atrial pressure was increased to 14 mmHg by inflation of left atrial balloon, PI increased to 18 mmHg. IR was 1.6 mmHg.l-1.min. Again, hypoxic ventilation caused an isolated change in PI. Hypoxia increased PI from 18 to 28 mmHg (P less than 0.01). As in the condition of normal left atrial pressure, hypoxic ventilation did not affect IR. We conclude that, in an anesthetized intact canine preparation, hypoxic ventilation causes an isolated increase in the extrapolated pressure intercept of the pulmonary P-Q relationship. Furthermore the effects of hypoxic ventilation on pulmonary P-Q characteristics are not affected by the resting left atrial pressure.

Influence of heart rate and left atrial pressure on pulmonary venous flow pattern in dogs

1994 ◽  
Vol 266 (6) ◽  
pp. H2296-H2302 ◽  
Author(s):  
T. Steen ◽  
B. M. Voss ◽  
O. A. Smiseth
Keyword(s):  
Heart Rate ◽  
Flow Pattern ◽  
Flow Rate ◽  
Left Atrial ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Mean Flow ◽  
Venous Flow ◽  
Pulmonary Venous Flow ◽  
The Relationship

In six open-chest anesthetized dogs we investigated the effect of heart rate (HR) on the relationship between left atrial pressure (LAP) and pulmonary venous flow (QPV). QPV was measured by ultrasonic transit time during volume loading and right atrial pacing. Consistent with previous studies, we found a negative correlation between LAP and mean flow rate during atrial systole divided by mean flow rate in the R-R interval. However, this relationship was shifted upward by tachycardia. The QPV maximum amplitude divided by mean flow rate in the R-R interval increased with loading but decreased with tachycardia. mean flow rate during ventricular systole divided by mean flow rate during the R-R interval increased with both loading and tachycardia. Regression coefficients for HR and LAP as predictors of these indexes were all significantly different from zero (P = 0.0001). We conclude that HR significantly influences the relationship between the QPV pattern and LAP. This could be a limitation of the pulmonary venous flow pattern as an indicator of left ventricular diastolic function.

Increasing oxygen tension dilates fetal pulmonary circulation via endothelium-derived relaxing factor

1993 ◽  
Vol 265 (1) ◽  
pp. H376-H380 ◽  
Author(s):  
M. H. Tiktinsky ◽  
F. C. Morin
Keyword(s):  
Blood Flow ◽  
Oxygen Tension ◽  
Hyperbaric Oxygen ◽  
Pulmonary Circulation ◽  
Left Atrial ◽  
Pulmonary Blood Flow ◽  
Absolute Pressure ◽  
Relaxing Factor ◽  
Pulmonary Arterial ◽  
Endothelium Derived Relaxing Factor

We examined the role of endothelium-derived relaxing factor (EDRF) in the increase in pulmonary blood flow caused by increasing oxygen tension in the lungs of the fetus. Fetal lambs at 133 days of gestation were instrumented for intrauterine measurement of pulmonary arterial, left atrial, and amniotic fluid pressure and pulmonary blood flow. Three days later oxygen tension in the pulmonary arterial blood of the fetus was doubled by having the ewe breathe 100% oxygen at 3 atm absolute pressure. In the control fetuses (n = 5), hyperbaric oxygenation increased pulmonary blood flow eightfold. Blocking EDRF production by infusing 45 mg of NG-monomethyl-L-arginine into the superior vena cava of the fetus over 5 min starting 30 min after the beginning of hyperbaric oxygen reversed the increase in pulmonary blood flow (n = 5). Blocking EDRF production by infusing NG-nitro-L-arginine at 1 mg/min for 60 min starting 30 min before hyperbaric oxygen blunted the initial increase in pulmonary blood flow and eliminated it by the end of the experiment (n = 5). As hyperbaric oxygen did not significantly alter pulmonary arterial or left atrial pressure, changes in pulmonary vascular conductance paralleled those in pulmonary blood flow. We conclude that the majority of the vasodilation of the fetal pulmonary circulation caused by increasing oxygen tension is mediated by EDRF. We speculate that EDRF is involved in maintaining low vascular tone at the relatively high oxygen tension of the postnatal lung.

Blunted hypoxic pulmonary vasoconstriction by increased lung vascular pressures

1975 ◽  
Vol 38 (5) ◽  
pp. 846-850 ◽  
Author(s):  
J. L. Benumof ◽  
E. A. Wahrenbrock
Keyword(s):  
Blood Flow ◽  
Left Atrial ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Main Pulmonary Artery ◽  
Lower Lobe ◽  
Respiratory Alkalosis ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Pulmonary Vasoconstriction ◽  
Lung Vessels

We tested the hypothesis that increased pressures within the lung vessels would inhibit hypoxic pulmonary vasoconstriction at all levels of alveolar CO2 tension. Selective hypoxia of the left lower lobe of the lung in open chested dogs caused the electromagnetically measured blood flow to the lobe to decrease 51 plus or minus 4 (SE) percent and its vascular resistance to increase 132 plus or minus 13 percent. Pressure and blood flow in the main pulmonary artery and left atrial pressure did not change during the hypoxic response. Stepwise increments in left artrial and pulmonary arterial pressures induced either by inflating a left atrial balloon or infusing dextran, progressively diminished the vasoconstrictive response to hypoxia. The response was usually abolished when left atrial pressure reached 25 mmHg. For all vascular pressures, hypoxic vasoconstriction was blunted by hypocapnic alkalosis but not enhanced by hypercapnia. We conclude that the redistribution of blood flow away from an hypoxic lobe of the lung to lobes with high Po2 was greatly attenuated by increasing pressures within lung vessels or by inducing respiratory alkalosis.

scholarly journals Measurement of pulmonary blood flow by fractal analysis of flow heterogeneity in isolated canine lungs

1996 ◽  
Vol 81 (5) ◽  
pp. 2039-2045 ◽  
Author(s):  
Scott A. Barman ◽  
Laryssa L. McCloud ◽  
John D. Catravas ◽  
Ina C. Ehrhart
Keyword(s):  
Blood Flow ◽  
Fractal Dimension ◽  
Fractal Analysis ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Blood Flow Rate ◽  
Blood Flow Distribution ◽  
Flow Rates ◽  
Flow Heterogeneity ◽  
Lung Lobes

Barman, Scott A., Laryssa L. McCloud, John D. Catravas, and Ina C. Ehrhart. Measurement of pulmonary blood flow by fractal analysis of flow heterogeneity in isolated canine lungs. J. Appl. Physiol. 81(5): 2039–2045, 1996.—Regional heterogeneity of lung blood flow can be measured by analyzing the relative dispersion (RD) of mass (weight)-flow data. Numerous studies have shown that pulmonary blood flow is fractal in nature, a phenomenon that can be characterized by the fractal dimension and the RD for the smallest realizable volume element (piece size). Although information exists for the applicability of fractal analysis to pulmonary blood flow in whole animal models, little is known in isolated organs. Therefore, the present study was done to determine the effect of blood flow rate on the distribution of pulmonary blood flow in the isolated blood-perfused canine lung lobe by using fractal analysis. Four different radiolabeled microspheres (141Ce,95Nb,85Sr, and51Cr), each 15 μm in diameter, were injected into the pulmonary lobar artery of isolated canine lung lobes ( n = 5) perfused at four different flow rates ( flow 1 = 0.42 ± 0.02 l/min; flow 2 = 1.12 ± 0.07 l/min; flow 3 = 2.25 ± 0.17 l/min; flow 4 = 2.59 ± 0.17 l/min), and the pulmonary blood flow distribution was measured. The results of the present study indicate that under isogravimetric blood flow conditions, all regions of horizontally perfused isolated lung lobes received blood flow that was preferentially distributed to the most distal caudal regions of the lobe. Regional pulmonary blood flow in the isolated perfused canine lobe was heterogeneous and fractal in nature, as measured by the RD. As flow rates increased, fractal dimension values (averaging 1.22 ± 0.08) remained constant, whereas RD decreased, reflecting more homogeneous blood flow distribution. At any given blood flow rate, high-flow areas of the lobe received a proportionally larger amount of regional flow, suggesting that the degree of pulmonary vascular recruitment may also be spatially related.

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