Pulmonary Blood Flow Redistribution with Low Levels of Positive End-expiratory Pressure 

1998 ◽  
Vol 88 (5) ◽  
pp. 1291-1299 ◽  
Author(s):  
Harry J. Kallas ◽  
Karen B. Domino ◽  
Robb W. Glenny ◽  
Emily A. Anderson ◽  
Michael P. Hlastala
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Zone Model ◽  
Structural Factors ◽  
Positive End Expiratory Pressure ◽  
Mechanically Ventilated ◽  
Anesthetized Dogs ◽  
Low Levels ◽  
Ventilation And Perfusion ◽  
Lung Zone

Background Recent studies have questioned the importance of the gravitational model of pulmonary perfusion. Because low levels of positive end-expiratory pressure (PEEP) are commonly used during anesthesia, the authors studied the distribution of pulmonary blood flow with low levels of PEEP using a high spatial resolution technique. They hypothesized that if hydrostatic factors were important in the distribution of pulmonary blood flow, PEEP would redistribute flow to more dependent lung regions. Methods The effects of zero cm H2O PEEP and 5 cm H2O PEEP on pulmonary gas exchange were studied using the multiple inert gas elimination technique; the distribution of pulmonary blood flow, using fluorescent-labeled microspheres, was also investigated in mechanically ventilated, pentobarbital-anesthetized dogs. The lungs were removed, cleared of blood, dried at total lung capacity, and then cubed to obtain approximately 1,000 small pieces of lung (approximately 1.7 cm3). Results Positive end-expiratory pressure increased the partial pressure of oxygen by 6 +/- 2 mmHg (P < 0.05) and reduced all measures of ventilation and perfusion heterogeneity (P < 0.05). By reducing flow to nondependent ventral lung regions and increasing flow to dependent dorsal lung regions, PEEP increased (P < 0.05) the dorsal-to-ventral gradient. Redistribution of blood flow with PEEP accounted for 7 +/- 3%, whereas structural factors accounted for 93 +/- 3% of the total variance in blood flow. Conclusions The increase in dependent-to-nondependent gradient with PEEP is partially consistent with the gravitationally based lung zone model. However, the results emphasize the greater importance of anatomic factors in determining the distribution of pulmonary blood flow.

Pulmonary Blood Flow Redistribution with Low Levels of Positive End-Expiratory Pressure

1999 ◽  
Vol 43 (1) ◽  
pp. 37
Author(s):  
HARRY J. KALLAS ◽  
KAREN B. DOMINO ◽  
ROBB W. GLENNY ◽  
EMILY A. ANDERSON ◽  
MICHAEL P. HLASTALA
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Positive End Expiratory Pressure ◽  
Low Levels ◽  
Blood Flow Redistribution

Effects of Positive End-Expiratory Pressure and Body Position on Pulmonary Blood Flow Redistribution in Mechanically Ventilated Normal Pigs

CHEST Journal ◽  
2002 ◽  
Vol 122 (3) ◽  
pp. 998-1005 ◽  
Author(s):  
Jean-Christophe Richard ◽  
Francois Decailliot ◽  
Marc Janier ◽  
Guy Annat ◽  
Claude Guérin
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Body Position ◽  
Positive End Expiratory Pressure ◽  
Mechanically Ventilated ◽  
Blood Flow Redistribution

Pulmonary blood flow and tissue volume: model analysis of rebreathing estimation methods

1983 ◽  
Vol 55 (1) ◽  
pp. 205-211 ◽  
Author(s):  
G. M. Burma ◽  
G. M. Saidel
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Breathing Pattern ◽  
Estimation Methods ◽  
Balance Model ◽  
Mass Balance Model ◽  
Volume Model ◽  
Dynamic Mass ◽  
Ventilation And Perfusion ◽  
Rebreathing Methods

As the basis for comparing rebreathing methods of estimating pulmonary blood flow (Q) and tissue-capillary volume (Vtc), we use a dynamic mass-balance model for gas species having different physicochemical properties (e.g., He, CO, C2H2). The model accounts for the effects of ventilation and perfusion inhomogeneities, breathing pattern variation, lung and rebreathing-bag volumes, and recirculation. Also, we examine the variability of the estimates caused by random error. In addition to analyzing two well-known methods, we show how an appropriate synthesis of these methods can lead to improved estimates.

PEEP only partly restores disturbed distribution of regional pulmonary blood flow in lung injury

1998 ◽  
Vol 274 (1) ◽  
pp. H209-H216
Author(s):  
M. Kleen ◽  
B. Zwissler ◽  
K. Messmer
Keyword(s):  
Blood Flow ◽  
Fractal Dimension ◽  
Oleic Acid ◽  
Lung Injury ◽  
Pulmonary Blood Flow ◽  
Glass Bead ◽  
Relative Dispersion ◽  
Anesthetized Dogs ◽  
Peep Ventilation ◽  
Bead Injection

The effects of lung injury, positive end-expiratory pressure (PEEP), and norepinephrine on heterogeneity of regional pulmonary blood flow (rPBF, radioactive microspheres) were investigated. We hypothesized that lung injury increases heterogeneity of rPBF and that PEEP ventilation reduces these effects. Heterogeneity of rPBF is scale dependent and was therefore assessed in detail. Local correlation (ρ), relative dispersion (RD), fractal dimension (D), perfusion gradients, and histograms of rPBF each measures a different aspect of heterogeneity. In eight anesthetized dogs, lung injury was induced with oleic acid and glass bead injection. Afterward, PEEP of 10–20 cmH2O was instituted. Norepinephrine was infused at 20 cmH2O PEEP. Heterogeneity increased upon lung injury (ρ, 0.44 ± 0.09 vs. 0.24 ± 0.09; RD, 0.36 ± 0.06 vs. 0.64 ± 0.12; both P ≤ 0.05), but fractal dimension remained constant. PEEP did not change ρ, RD, or D. Perfusion gradients were reversed after lung injury (right, −27 ± 18 vs. 196 ± 115%; left, −24 ± 18 vs. 282 ± 184%; P ≤ 0.05). PEEP (10 cmH2O) reduced gradients (116 ± 73 and 143 ± 62%, respectively; P ≤ 0.05). Norepinephrine, in part, further reduced gradients (right, 50 ± 58%; P ≤ 0.05; left, 102 ± 94%; P = NS). We conclude that oleic acid- and glass bead-induced lung injury produces abnormal distribution of rPBF. Of these changes, application of PEEP only reverses perfusion gradients.

Hypopnea consequent to reduced pulmonary blood flow in the dog

1979 ◽  
Vol 46 (6) ◽  
pp. 1171-1177 ◽  
Author(s):  
R. W. Stremel ◽  
B. J. Whipp ◽  
R. Casaburi ◽  
D. J. Huntsman ◽  
K. Wasserman
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Blood Gases ◽  
Left Ventricular ◽  
Intact Group ◽  
Average Decrease ◽  
Ventilatory Responses ◽  
Arterial Blood ◽  
Cervical Vagotomy ◽  
Anesthetized Dogs

The ventilatory responses to diminished pulmonary blood flow (Qc), as a result of partial cardiopulmonary bypass (PCB), were studied in chloralose-urethan-anesthetized dogs. Qc was reduced by diverting vena caval blood through a membrane gas exchanger and returning it to the ascending aorta. PCB flows of 400--1,600 ml/min were utilized for durations of 2--3 min. Decreasing Qc, while maintaining systemic arterial blood gases and perfusion, results in a significant (P less than 0.05) decrease in expiratory ventilation (VE) (15.9%) and alveolar ventilation (VA) (31.0%). The ventilatory decreases demonstrated for this intact group persist after bilateral cervical vagotomy (Vx), carotid body and carotid sinus denervation (Cx), and combined Vx and Cx. The changes in VE and VA were significantly (P less than 0.001) correlated with VCO2 changes, r = 0.80 and r = 0.93, respectively. These ventilatory changes were associated with an overall average decrease in left ventricular PCO2 of 2.1 Torr; this decrease was significant (P less than 0.05) only in the intact and Cx groups. Decreasing pulmonary blood flow results in a decrease in ventilation that may be CO2 related; however, the exact mechanism remains obscure but must have a component that is independent of vagally mediated cardiac and pulmonary afferents and peripheral baroreceptor and chemoreceptor afferents.

Influence of Anaesthesia on the Regional Distribution of Perfusion and Ventilation in the Lung

1970 ◽  
Vol 38 (4) ◽  
pp. 451-460 ◽  
Author(s):  
G. H. Hulands ◽  
R. Greene ◽  
L. D. Iliff ◽  
J. F. Nunn
Keyword(s):  
Blood Flow ◽  
Lung Volume ◽  
Pulmonary Blood Flow ◽  
Artificial Ventilation ◽  
Pulmonary Ventilation ◽  
Regional Distribution ◽  
Residual Capacity ◽  
Arterial Po2 ◽  
Ventilation And Perfusion ◽  
Perfusion Unit

1. Distribution of lung volume, pulmonary ventilation and perfusion were studied in supine patients before and during anaesthesia with paralysis and artificial ventilation. Inspired gas and pulmonary blood flow were measured with 133xenon and the chest was scanned with vertically moving counters at a lung volume of 1 litre above functional residual capacity. 2. Ventilation/unit lung volume was slightly greater and perfusion/unit lung volume substantially greater during anaesthesia in the dependent parts of the lungs. The spread of ventilation/perfusion ratios in supine conscious patients was small in comparison with that reported in upright conscious patients. During anaesthesia and artificial ventilation, the inequality of ventilation to perfusion was marginally increased in three of the four patients. 3. Ventilation/perfusion inequality alone was insufficient to explain the alveolar—arterial Po2 difference usually observed during anaesthesia.

Pulmonary blood flow redistribution by increased gravitational force

1998 ◽  
Vol 84 (4) ◽  
pp. 1278-1288 ◽  
Author(s):  
Michael P. Hlastala ◽  
Myron A. Chornuk ◽  
David A. Self ◽  
Harry J. Kallas ◽  
John W. Burns ◽  
...  
Keyword(s):  
Blood Flow ◽  
Coefficient Of Variation ◽  
Pulmonary Blood Flow ◽  
Inertial Force ◽  
Blood Gases ◽  
Zone Model ◽  
Arterial Blood ◽  
Entire Experiment ◽  
Air Force Base ◽  
Laboratory Centrifuge

This study was undertaken to assess the influence of gravity on the distribution of pulmonary blood flow (PBF) using increased inertial force as a perturbation. PBF was studied in unanesthetized swine exposed to −G x (dorsal-to-ventral direction, prone position), where G is the magnitude of the force of gravity at the surface of the Earth, on the Armstrong Laboratory Centrifuge at Brooks Air Force Base. PBF was measured using 15-μm fluorescent microspheres, a method with markedly enhanced spatial resolution. Each animal was exposed randomly to −1, −2, and −3 G x . Pulmonary vascular pressures, cardiac output, heart rate, arterial blood gases, and PBF distribution were measured at each G level. Heterogeneity of PBF distribution as measured by the coefficient of variation of PBF distribution increased from 0.38 ± 0.05 to 0.55 ± 0.11 to 0.72 ± 0.16 at −1, −2, and −3 G x , respectively. At −1 G x , PBF was greatest in the ventral and cranial and lowest in the dorsal and caudal regions of the lung. With increased −G x , this gradient was augmented in both directions. Extrapolation of these values to 0 G predicts a slight dorsal (nondependent) region dominance of PBF and a coefficient of variation of 0.22 in microgravity. Analysis of variance revealed that a fixed component (vascular structure) accounted for 81% and nonstructure components (including gravity) accounted for the remaining 19% of the PBF variance across the entire experiment (all 3 gravitational levels). The results are inconsistent with the predictions of the zone model.

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.

Sign in / Sign up

Export Citation Format

Share Document