0
Technical Brief

Ultrasound Assessment of Ex Vivo Lung Tissue Properties Using a Fluid-Filled Negative Pressure Bath

[+] Author and Article Information
Sarah Duenwald-Kuehl

Department of Orthopedics and Rehabilitation,
University of Wisconsin-Madison,
Madison, WI 53705;
Department of Biomedical Engineering,
University of Wisconsin-Madison,
Madison, WI 53706

Melissa L. Bates

Department of Pediatrics and the John Rankin
Laboratory of Pulmonary Medicine,
University of Wisconsin-Madison,
Madison, WI 53705

Sonia Y. Cortes

Department of Orthopedics and Rehabilitation,
University of Wisconsin-Madison,
Madison, WI 53705;
Department of Biomedical Engineering,
University of Wisconsin-Madison,
Madison, WI 53706

Marlowe W. Eldridge

Department of Pediatrics and the John Rankin
Laboratory of Pulmonary Medicine,
University of Wisconsin-Madison,
Madison, WI 53705;
Departments of Biomedical Engineering and Kinesiology,
University of Wisconsin-Madison,
Madison, WI 53706

Ray Vanderby

Department of Orthopedics and Rehabilitation,
University of Wisconsin-Madison,
Madison, WI 53705;
Department of Biomedical Engineering,
University of Wisconsin-Madison,
Madison, WI 53706;
Materials Science Program,
University of Wisconsin-Madison,
Madison, WI 53706
e-mail: vanderby@ortho.wisc.edu

1Present address: Room 5059, 1111 Highland Ave, Madison, WI 53705.

2Corresponding author.

Manuscript received October 28, 2013; final manuscript received April 9, 2014; accepted manuscript posted May 8, 2014; published online May 29, 2014. Assoc. Editor: Jeffrey Ruberti.

J Biomech Eng 136(7), 074504 (May 29, 2014) (5 pages) Paper No: BIO-13-1509; doi: 10.1115/1.4027611 History: Received October 28, 2013; Revised April 09, 2014; Accepted May 04, 2014

A relationship between tendon stress and strain and ultrasonic echo intensity has previously been defined in tendons, demonstrating a correlation between tissue stiffness and echo intensity. An analogous relationship between volume-dependent pressure changes and echo intensity changes in inflating lungs would indicate a correlation between lung compliance and echo intensity. Lung compliance is an important metric to diagnose pathologies which affect lung tissue mechanics, such as emphysema and cystic fibrosis. The goal of this study is to demonstrate a correlation between ultrasound echo intensity and lung tissue mechanics in an ex vivo model using a fluid-filled negative pressure bath design which provides a controlled environment for ultrasonic and mechanical measurements. Lungs from 4 male Sprague-Dawley rats were removed and mechanically tested via inflation and deflation in a negative pressure chamber filled with hetastarch. Specific volumes (1, 2, 3, and 4 mL) were removed from the chamber using a syringe to create negative pressure, which resulted in lung inflation. A pressure transducer recorded the pressure around the lungs. From these data, lung compliance was calculated. Ultrasound images were captured through the chamber wall to determine echo intensity (grayscale brightness in the ultrasound image), which was then related to mechanical parameters. Ultrasound images of the lung were successfully captured through the chamber wall with sufficient resolution to deduce echo intensity changes in the lung tissue. Echo intensity (0–255 scale) increased with volumetric changes (18.4 ± 5.5, 22.6 ± 5.1, 26.1 ± 7.5, and 42.9 ± 19.5 for volumetric changes of 1, 2, 3, and 4 mL) in a pattern similar to pressure (−6.8 ± 1.7, −6.8 ± 1.4, −9.4 ± 0.7, and −16.9 ± 6.8 cm H2O for 1, 2, 3, and 4 mL), reflecting changes in lung compliance. Measured rat lung tissue compliance was comparable to reported values from ex vivo lungs (0.178 ± 0.067, 0.378 ± 0.051, 0.427 ± 0.062, and 0.350 ± 0.160 mL/cm H20 for 1, 2, 3, and 4 mL), supporting proof of concept for the experimental method. Changes in echo intensity reflected changes in lung compliance in this ex vivo model, thus, supporting our hypothesis that the stiffness-related changes in echo intensity originally seen in tendon can be similarly detected in lung tissue. The presented ultrasound-based methods allowed measurement of local lung tissue compliance in a controlled environment, however, the methods could be expanded to facilitate both ex vivo and in vivo studies.

FIGURES IN THIS ARTICLE
<>
Copyright © 2014 by ASME
Your Session has timed out. Please sign back in to continue.

References

West, J. B., 2008, Respiratory Physiology: The Essentials, Lippincott Williams & Wilkins, Baltimore/Philadelphia.
Suki, B., and Bates, J. H. T., 2011, “Lung Tissue Mechanics as an Emergent Phenomenon,” J. Appl. Physiol., 110(4), pp. 1111–1118. [CrossRef]
Bates, J. H. T., 2009, Lung Mechanics: An Inverse Modeling Approach, Vol. 67, Cambridge University, Cambridge, UK.
Chiron, C., Gaultier, C., Boule, M., Grimfeld, A., and Girard, F., 1984, “Lung Function in Children With Hypersensitivity Pneumonitis,” Eur. J. Respir. Dis., 65(2), pp. 79–91.
Geirsson, A. J., Wollheim, F. A., and Akesson, A., 2001, “Disease Severity of 100 Patients With Systemic Sclerosis Over a Period of 14 Years: Using a Modified Medsger Scale,” Ann. Rheum. Dis., 60(12), pp. 1117–1122. [CrossRef]
Simbruner, G., Coradello, H., Lubec, G., Pollak, A., and Salzer, H., 1982, “Respiratory Compliance of Newborns After Birth and Its Prognostic Value for the Course and Outcome of Respiratory Disease,” Respiration, 43(6), pp. 414–423. [CrossRef]
Duenwald, S., Kobayashi, H., Frisch, K., Lakes, R., and Vanderby, Jr., R., 2011, “Ultrasound Echo is Related to Stress and Strain in Tendon,” J. Biomech., 44(3), pp. 424–429. [CrossRef]
Duenwald-Kuehl, S., Kobayashi, H., Lakes, R., and Vanderby, R., 2012, “Time-Dependent Ultrasound Echo Changes Occur in Tendon During Viscoelastic Testing,” ASME J. Biomech. Eng., 134(11), p. 111006. [CrossRef]
Duenwald-Kuehl, S., Lakes, R., and Vanderby, Jr., R., 2012, “Strain-Induced Damage Reduces Echo Intensity Changes in Tendon During Loading,” J. Biomech., 45(9), pp. 1607–1611. [CrossRef]
Chamberlain, C. S., Duenwald-Kuehl, S. E., Okotie, G., Brounts, S. H., Baer, G. S., and Vanderby, R., 2013, “Temporal Healing in Rat Achilles Tendon: Ultrasound Correlations,” Ann. Biomed. Eng., 41(3), pp. 477–487. [CrossRef]
Reissig, A., Copetti, R., and Kroegel, C., 2011, “Current Role of Emergency Ultrasound of the Chest*,” Crit. Care Med., 39(4), pp. 839–845. [CrossRef]
AVMA, 2007, “AVMA Guidelines on Euthanasia (Formerly Report of the AVMA Panel on Euthanasia),” June 2007.
Bates, M. L., Fulmer, B. R., Farrell, E. T., Drezdon, A., Pegelow, D. F., Conhaim, R. L., and Eldridge, M. W., 2012, “Hypoxia Recruits Intrapulmonary Arteriovenous Pathways in Intact Rats But Not Isolated Rat Lungs,” J. Appl. Physiol., 112(11), pp. 1915–1920. [CrossRef]
Conhaim, R. L., and Harms, B. A., 1993, “Perfusion of Alveolar Septa in Isolated Rat Lungs in Zone 1,” J. Appl. Physiol., 75(2), pp. 704–711.
Hulse, J. D., and Yacobi, A., 1983, “Hetastarch: An Overview of the Colloid and Its Metabolism,” Ann. Pharmacother., 17(5), pp. 334–341.
Palecek, F., 1969, “Measurement of Ventilatory Mechanics in the Rat,” J. Appl. Physiol., 27(1), pp. 149–156.
Chaudhary, N. I., Schnapp, A., and Park, J. E., 2006, “Pharmacologic Differentiation of Inflammation and Fibrosis in the Rat Bleomycin Model,” Am. J. Respir. Crit. Care Med., 173(7), pp. 769–776. [CrossRef]
Bellofiore, S., Eidelman, D. H., Macklem, P. T., and Martin, J. G., 1989, “Effects of Elastase-Induced Emphysema on Airway Responsiveness to Methacholine in Rats,” J. Appl. Physiol., 66(2), pp. 606–612.
Kobayashi, H., and Vanderby, R., 2007, “Acoustoelastic Analysis of Reflected Waves in Nearly Incompressible, Hyper-Elastic Materials: Forward and Inverse Problems,” J. Acoust. Soc. Am., 121(2), pp. 879–887. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

Mechanical testing apparatus. The fluid-filled, plastic-walled chamber is conducive for ultrasound. The sealed bath had three outlets to connect the lung, the pressure transducer and a syringe. Specific volumes (1, 2, 3, and 4 mL) were removed from the box using a 10 mL syringe to create a negative pressure and inflate the lung. The same volume was returned to the box in order to deflate the lung. The pressure was measured using a pressure transducer. The lung was connected to the bath using a catheter which was open to the atmosphere. The ultrasound transducer (top right) was positioned longitudinally along the bath to record ultrasound videos simultaneously with mechanical data. The dotted box outlines the region of ultrasound analysis.

Grahic Jump Location
Fig. 2

Ultrasound image collected simultaneously with pressure measurements. The base of the lungs is shown in this image. A sample ROI is outlined on the left lung.

Grahic Jump Location
Fig. 3

Representative (a) pressure change and (b) ultrasound echo intensity data during inflation and deflation, collected for three trials on one lung. Echo intensity changes were taken near the base of the left lung. The pressure waveform and echo intensity waveforms are essentially the same shape in time.

Grahic Jump Location
Fig. 4

Average changes in pressure and echo intensity from all samples at all volume changes. Both parameters demonstrate increased changes with increased volume demonstrating similar trends. Error bars represent standard error (n = 4).

Grahic Jump Location
Fig. 5

Relationship between overall compliance and echo intensity

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In