Mechanism by Which a Sustained Inflation Can Worsen Oxygenation in Acute Lung Injury

Background Sustained lung inflations (recruitment maneuvers [RMs]) are occasionally used during mechanical ventilation of patients with acute lung injury to restore aeration to atelectatic alveoli. However, RMs do not improve, and may even worsen, gas exchange in a fraction of these patients. In this study, the authors sought to determine the mechanism by which an RM can impair gas exchange in acute lung injury. Methods The authors selected a model of acute lung injury that was unlikely to exhibit sustained recruitment in response to a lung inflation. In five sheep, lung injury was induced by lavage with 0.2% polysorbate 80 in saline. Positron emission tomography and [13N]nitrogen were used to assess regional lung function in dependent, middle, and nondependent lung regions. Physiologic data and positron emission scans were collected before and 5 min after a sustained inflation (continuous positive airway pressure of 50 cm H2O for 30 s). Results All animals showed greater loss of aeration and higher perfusion and shunting blood flow in the dependent region. After the RM, Pao2 decreased in all animals by 35 +/- 22 mmHg (P < 0.05). This decrease in Pao2 was associated with redistribution of pulmonary blood flow from the middle, more aerated region to the dependent, less aerated region (P < 0.05) and with an increase in the fraction of pulmonary blood flow that was shunted in the dependent region (P < 0.05). Neither respiratory compliance nor aeration of the dependent region improved after the RM. Conclusions When a sustained inflation does not restore aeration to atelectatic regions, it can worsen oxygenation by increasing the fraction of pulmonary blood flow that is shunted in nonaerated regions.

Download Full-text

Effects of Vaporized Perfluorocarbon on Pulmonary Blood Flow and Ventilation/Perfusion Distribution in a Model of Acute Respiratory Distress Syndrome

Anesthesiology ◽

10.1097/00000542-200112000-00021 ◽

2001 ◽

Vol 95 (6) ◽

pp. 1414-1421 ◽

Cited By ~ 12

Author(s):

Matthias Hübler ◽

Jennifer E. Souders ◽

Erin D. Shade ◽

Nayak L. Polissar ◽

Carmel Schimmel ◽

...

Keyword(s):

Blood Flow ◽

Oleic Acid ◽

Gas Exchange ◽

Lung Injury ◽

Repeated Measures ◽

Pulmonary Blood Flow ◽

Analysis Of Covariance ◽

Inert Gas ◽

Low Flow ◽

Repeated Measures Analysis

Background Perfluorocarbon (PFC) liquids are known to improve gas exchange and pulmonary function in various models of acute respiratory failure. Vaporization has been recently reported as a new method of delivering PFC to the lung. Our aim was to study the effect of PFC vapor on the ventilation/perfusion (VA/Q) matching and relative pulmonary blood flow (Qrel) distribution. Methods In nine sheep, lung injury was induced using oleic acid. Four sheep were treated with vaporized perfluorohexane (PFX) for 30 min, whereas the remaining sheep served as control animals. Vaporization was achieved using a modified isoflurane vaporizer. The animals were studied for 90 min after vaporization. VA/Q distributions were estimated using the multiple inert gas elimination technique. Change in Qrel distribution was assessed using fluorescent-labeled microspheres. Results Treatment with PFX vapor improved oxygenation significantly and led to significantly lower shunt values (P < 0.05, repeated-measures analysis of covariance). Analysis of the multiple inert gas elimination technique data showed that animals treated with PFX vapor demonstrated a higher VA/Q heterogeneity than the control animals (P < 0.05, repeated-measures analysis of covariance). Microsphere data showed a redistribution of Qrel attributable to oleic acid injury. Qrel shifted from areas that were initially high-flow to areas that were initially low-flow, with no difference in redistribution between the groups. After established injury, Qrel was redistributed to the nondependent lung areas in control animals, whereas Qrel distribution did not change in treatment animals. Conclusion In oleic acid lung injury, treatment with PFX vapor improves gas exchange by increasing VA/Q heterogeneity in the whole lung without a significant change in gravitational gradient.

Download Full-text

Response to Inhaled Nitric Oxide in Acute Lung Injury Depends on Distribution of Pulmonary Blood Flow Prior to Its Administration

American Journal of Respiratory and Critical Care Medicine ◽

10.1164/ajrccm.159.2.9806133 ◽

1999 ◽

Vol 159 (2) ◽

pp. 563-570 ◽

Cited By ~ 27

Author(s):

RENÉ GUST ◽

TIMOTHY J. McCARTHY ◽

JAMES KOZLOWSKI ◽

ALAN H. STEPHENSON ◽

DANIEL P. SCHUSTER

Keyword(s):

Nitric Oxide ◽

Blood Flow ◽

Acute Lung Injury ◽

Lung Injury ◽

Pulmonary Blood Flow ◽

Inhaled Nitric Oxide

Download Full-text

Distribution of pulmonary blood flow and total lung water during partial liquid ventilation in acute lung injury

Surgery ◽

10.1016/s0039-6060(97)90023-4 ◽

1997 ◽

Vol 122 (2) ◽

pp. 313-323 ◽

Cited By ~ 36

Author(s):

Paul G Gauger ◽

Michael C Overbeck ◽

Robert A Koeppe ◽

Barry L Shulkin ◽

Julia N Hrycko ◽

...

Keyword(s):

Blood Flow ◽

Acute Lung Injury ◽

Lung Injury ◽

Pulmonary Blood Flow ◽

Partial Liquid Ventilation ◽

Lung Water ◽

Liquid Ventilation

Download Full-text

Hemodilution during Venous Gas Embolization Improves Gas Exchange, without Altering V̇A/Q̇ or Pulmonary Blood Flow Distributions

Anesthesiology ◽

10.1097/00000542-199912000-00041 ◽

1999 ◽

Vol 91 (6) ◽

pp. 1861-1861 ◽

Cited By ~ 12

Author(s):

Steven Deem ◽

Steven McKinney ◽

Nayak L. Polissar ◽

Richard G. Hedges ◽

Erik R. Swenson

Keyword(s):

Blood Flow ◽

Gas Exchange ◽

Lung Injury ◽

Partial Pressure ◽

Pulmonary Blood Flow ◽

Flow Distribution ◽

Arterial Oxygen ◽

Control Group ◽

Blood Flow Distribution ◽

Over Time

Background Isovolemic anemia results in improved gas exchange in rabbits with normal lungs but in relatively poorer gas exchange in rabbits with whole-lung atelectasis. In the current study, the authors characterized the effects of hemodilution on gas exchange in a distinct model of diffuse lung injury: venous gas embolization. Methods Twelve anesthetized rabbits were mechanically ventilated at a fixed rate and volume. Gas embolization was induced by continuous infusion of nitrogen via an internal jugular venous catheter. Serial hemodilution was performed in six rabbits by simultaneous withdrawal of blood and infusion of an equal volume of 6% hetastarch; six rabbits were followed as controls over time. Measurements included hemodynamic parameters and blood gases, ventilation-perfusion (V(A)/Q) distribution (multiple inert gas elimination technique), pulmonary blood flow distribution (fluorescent microspheres), and expired nitric oxide (NO; chemoluminescence). Results Venous gas embolization resulted in a decrease in partial pressure of arterial oxygen (PaO2) and an increase in partial pressure of arterial carbon dioxide (PaCO2), with markedly abnormal overall V(A)/Q distribution and a predominance of high V(A)/Q areas. Pulmonary blood flow distribution was markedly left-skewed, with low-flow areas predominating. Hematocrit decreased from 30+/-1% to 11+/-1% (mean +/- SE) with hemodilution. The alveolar-arterial PO2 (A-aPO2) difference decreased from 375+/-61 mmHg at 30% hematocrit to 218+/-12.8 mmHg at 15% hematocrit, but increased again (301+/-33 mmHg) at 11% hematocrit. In contrast, the A-aPO2 difference increased over time in the control group (P < 0.05 between groups over time). Changes in PaO2 in both groups could be explained in large part by variations in intrapulmonary shunt and mixed venous oxygen saturation (SvO2); however, the improvement in gas exchange with hemodilution was not fully explained by significant changes in V(A)/Q or pulmonary blood flow distributions, as quantitated by the coefficient of variation (CV), fractal dimension, and spatial correlation of blood flow. Expired NO increased with with gas embolization but did not change significantly with time or hemodilution. Conclusions Isovolemic hemodilution results in improved oxygen exchange in rabbits with lung injury induced by gas embolization. The mechanism for this improvement is not clear.

Download Full-text

Regional puimonary blood flow, extravascular lung water and pulmonary vascular permeability measurements made with positron emission tomography before and after acute lung injury

Journal of Critical Care ◽

10.1016/s0883-9441(86)80064-8 ◽

1986 ◽

Vol 1 (2) ◽

pp. 110

Keyword(s):

Positron Emission Tomography ◽

Blood Flow ◽

Acute Lung Injury ◽

Lung Injury ◽

Extravascular Lung Water ◽

Emission Tomography ◽

Lung Water ◽

Pulmonary Vascular Permeability ◽

Positron Emission ◽

Before And After

Download Full-text

Effect of activated protein C on pulmonary blood flow and cytokine production in experimental acute lung injury

Intensive Care Medicine ◽

10.1007/s00134-007-0782-0 ◽

2007 ◽

Vol 33 (12) ◽

pp. 2199-2206 ◽

Cited By ~ 11

Author(s):

Jean-Christophe Richard ◽

Fabienne Bregeon ◽

Véronique Leray ◽

Didier Le Bars ◽

Nicolas Costes ◽

...

Keyword(s):

Blood Flow ◽

Acute Lung Injury ◽

Lung Injury ◽

Pulmonary Blood Flow ◽

Protein C ◽

Cytokine Production ◽

Activated Protein C

Download Full-text

Effect of acute lung injury on the spatial correlation of regional pulmonary blood flow

10.1117/12.174411 ◽

1994 ◽

Author(s):

Daniel P. Schuster ◽

Joanne Markham

Keyword(s):

Blood Flow ◽

Acute Lung Injury ◽

Lung Injury ◽

Spatial Correlation ◽

Pulmonary Blood Flow

Download Full-text

Changes in Pulmonary Blood Flow during Gaseous and Partial Liquid Ventilation in Experimental Acute Lung Injury

Anesthesiology ◽

10.1097/00000542-200012000-00016 ◽

2000 ◽

Vol 93 (6) ◽

pp. 1437-1445 ◽

Cited By ~ 6

Author(s):

Martin Max ◽

Bernd Nowak ◽

Rolf Dembinski ◽

Gernot Schulz ◽

Ralf Kuhlen ◽

...

Keyword(s):

Blood Flow ◽

Acute Lung Injury ◽

Lung Injury ◽

Pulmonary Blood Flow ◽

Arterial Oxygen ◽

Pulmonary Vasculature ◽

Emission Computed Tomography ◽

Partial Liquid Ventilation ◽

Arterial Oxygenation ◽

Liquid Ventilation

Background It has been proposed that partial liquid ventilation (PLV) causes a compression of the pulmonary vasculature by the dense perfluorocarbons and a subsequent redistribution of pulmonary blood flow from dorsal to better-ventilated middle and ventral lung regions, thereby improving arterial oxygenation in situations of acute lung injury. Methods After induction of acute lung injury by repeated lung lavage with saline, 20 pigs were randomly assigned to partial liquid ventilation with two sequential doses of 15 ml/kg perfluorocarbon (PLV group, n = 10) or to continued gaseous ventilation (GV group, n = 10). Single-photon emission computed tomography was used to study regional pulmonary blood flow. Gas exchange, hemodynamics, and pulmonary blood flow were determined in both groups before and after the induction of acute lung injury and at corresponding time points 1 and 2 h after each instillation of perfluorocarbon in the PLV group. Results During partial liquid ventilation, there were no changes in pulmonary blood flow distribution when compared with values obtained after induction of acute lung injury in the PLV group or to the animals submitted to gaseous ventilation. Arterial oxygenation improved significantly in the PLV group after instillation of the second dose of perfluorocarbon. Conclusions In the surfactant washout animal model of acute lung injury, redistribution of pulmonary blood flow does not seem to be a major factor for the observed increase of arterial oxygen tension during partial liquid ventilation.

Download Full-text