Newly Published
Critical Care Medicine  |   May 2019
Short-term Physiologic Consequences of Regional Pulmonary Vascular Occlusion in Pigs
Author Notes
  • From the Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy (T.L., V.C., S.B., T.M., A.Z., A.P.); and the Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy (T.L., A.S., T.M., A.Z., A.P.)
  • Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).
    Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).×
  • Submitted for publication August 27, 2018. Accepted for publication March 13, 2019.
    Submitted for publication August 27, 2018. Accepted for publication March 13, 2019.×
  • Acknowledgments: The authors are indebted to Lawrence R. Goodman, M.D., F.A.C.R., Cardiothoracic Imaging Section, Department of Radiology and Department of Pulmonary Medicine and Critical Care, Medical College of Wisconsin, Milwaukee, Wisconsin, for his useful suggestions; to Eleonora Carlesso, M.Sc., Department of Pathophysiology and Transplantation of the University of Milan, Milan, Italy, for her valuable statistical support and support with imaging processing; and to Stefano Gatti, M.D., and Daniele Dondossola, M.D., from the Center for Preclinical Research, Fondazione IRCCS Ca’ Granda-Ospedale Maggiore Policlinico of Milan, for their valuable support regarding surgical preparation.
    Acknowledgments: The authors are indebted to Lawrence R. Goodman, M.D., F.A.C.R., Cardiothoracic Imaging Section, Department of Radiology and Department of Pulmonary Medicine and Critical Care, Medical College of Wisconsin, Milwaukee, Wisconsin, for his useful suggestions; to Eleonora Carlesso, M.Sc., Department of Pathophysiology and Transplantation of the University of Milan, Milan, Italy, for her valuable statistical support and support with imaging processing; and to Stefano Gatti, M.D., and Daniele Dondossola, M.D., from the Center for Preclinical Research, Fondazione IRCCS Ca’ Granda-Ospedale Maggiore Policlinico of Milan, for their valuable support regarding surgical preparation.×
  • Correspondence: Address correspondence to Dr. Langer: Università degli Studi di Milano, 20122 Milan, Italy. Thomas.Langer@unimi.it. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Critical Care Medicine / Critical Care / Respiratory System / Technology / Equipment / Monitoring
Critical Care Medicine   |   May 2019
Short-term Physiologic Consequences of Regional Pulmonary Vascular Occlusion in Pigs
Anesthesiology Newly Published on May 7, 2019. doi:10.1097/ALN.0000000000002735
Anesthesiology Newly Published on May 7, 2019. doi:10.1097/ALN.0000000000002735
Abstract

Editor’s Perspective:

What We Already Know about This Topic:

  • After pulmonary artery occlusion (mimicking a pulmonary embolism), perfusion is redistributed to the rest of the lung tissue, but the distribution of ventilation is uncertain.

What This Article Tells Us That Is New:

  • Data from anesthetized pigs (uninjured lungs) indicates that the perfusion is redistributed as suspected. Similarly, ventilation is redistributed from nonperfused to perfused lung tissue. This limits the increase in dead space and is accompanied by less density in the occluded lung.

Background: Acute unilateral pulmonary arterial occlusion causes ventilation–perfusion mismatch of the affected lung area. A diversion of ventilation from nonperfused to perfused lung areas, limiting the increase in dead space, has been described. The hypothesis was that the occlusion of a distal branch of the pulmonary artery would cause local redistribution of ventilation and changes in regional lung densitometry as assessed with quantitative computed tomography.

Methods: In eight healthy, anesthetized pigs (18.5 ± 3.8 kg) ventilated with constant ventilatory settings, respiratory mechanics, arterial blood gases, and quantitative computed tomography scans were recorded at baseline and 30 min after the inflation of the balloon of a pulmonary artery catheter. Regional (left vs. right lung and perfused vs. nonperfused area) quantitative computed tomography was performed.

Results: The balloon always occluded a branch of the left pulmonary artery perfusing approximately 30% of lung tissue. Physiologic dead space increased (0.37 ± 0.17 vs. 0.43 ± 0.17, P = 0.005), causing an increase in Paco2 (39.8 [35.2 to 43.0] vs. 41.8 [37.5 to 47.1] mmHg, P = 0.008) and reduction in pH (7.46 [7.42 to 7.50] vs. 7.42 [7.38 to 7.47], P = 0.008). Respiratory system compliance was reduced (24.4 ± 4.2 vs. 22.8 ± 4.8 ml · cm H2O−1, P = 0.028), and the reduction was more pronounced in the left hemithorax. Quantitative analysis of the nonperfused lung area revealed a significant reduction in lung density (−436 [−490 to −401] vs. −478 [−543 to −474] Hounsfield units, P = 0.016), due to a reduction in lung tissue (90 ± 23 vs. 81 ± 22 g, P < 0.001) and an increase in air volume (70 ± 22 vs. 82 ± 26 ml, P = 0.022).

Conclusions: Regional pulmonary vascular occlusion is associated with a diversion of ventilation from nonperfused to perfused lung areas. This compensatory mechanism effectively limits ventilation perfusion mismatch. Quantitative computed tomography documented acute changes in lung densitometry after pulmonary vascular occlusion. In particular, the nonperfused lung area showed an increase in air volume and reduction in tissue mass, resulting in a decreased lung density.