Introducing a Custom-Designed Volume-Pressure Machine for Novel Measurements of Whole Lung Organ Viscoelasticity and Direct Comparisons Between Positive- and Negative-Pressure Ventilation

Samaneh Sattari; Crystal A Mariano; Swathi Vittalbabu; Jalene V Velazquez; Jessica Postma; Caleb Horst; Eric Teh; Tara M Nordgren; Mona Eskandari

doi:10.3389/fbioe.2020.578762

Introducing a Custom-Designed Volume-Pressure Machine for Novel Measurements of Whole Lung Organ Viscoelasticity and Direct Comparisons Between Positive- and Negative-Pressure Ventilation

Front Bioeng Biotechnol. 2020 Oct 21:8:578762. doi: 10.3389/fbioe.2020.578762. eCollection 2020.

Authors

Samaneh Sattari¹, Crystal A Mariano¹, Swathi Vittalbabu¹, Jalene V Velazquez^{2

3}, Jessica Postma⁴, Caleb Horst⁴, Eric Teh⁴, Tara M Nordgren^{2

3}, Mona Eskandari^{1

2

5}

Affiliations

¹ Department of Mechanical Engineering, University of California, Riverside, Riverside, CA, United States.
² BREATHE Center at the School of Medicine, University of California, Riverside, Riverside, CA, United States.
³ Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States.
⁴ CellScale Biomaterials Testing, Waterloo, ON, Canada.
⁵ Department of Bioengineering, University of California, Riverside, Riverside, CA, United States.

Abstract

Asthma, emphysema, COVID-19 and other lung-impacting diseases cause the remodeling of tissue structural properties and can lead to changes in conducting pulmonary volume, viscoelasticity, and air flow distribution. Whole organ experimental inflation tests are commonly used to understand the impact of these modifications on lung mechanics. Here we introduce a novel, automated, custom-designed device for measuring the volume and pressure response of lungs, surpassing the capabilities of traditional machines and built to range size-scales to accommodate both murine and porcine tests. The software-controlled system is capable of constructing standardized continuous volume-pressure curves, while accounting for air compressibility, yielding consistent and reproducible measures while eliminating the need for pulmonary degassing. This device uses volume-control to enable viscoelastic whole lung macromechanical insights from rate dependencies and pressure-time curves. Moreover, the conceptual design of this device facilitates studies relating the phenomenon of diaphragm breathing and artificial ventilation induced by pushing air inside the lungs. System capabilities are demonstrated and validated via a comparative study between ex vivo murine lungs and elastic balloons, using various testing protocols. Volume-pressure curve comparisons with previous pressure-controlled systems yield good agreement, confirming accuracy. This work expands the capabilities of current lung experiments, improving scientific investigations of healthy and diseased pulmonary biomechanics. Ultimately, the methodologies demonstrated in the manufacturing of this system enable future studies centered on investigating viscoelasticity as a potential biomarker and improvements to patient ventilators based on direct assessment and comparisons of positive- and negative-pressure mechanics.

Keywords: COVID-19; lung and respiratory mechanics; positive and negative pressure ventilation; pressure-volume curve; pulmonary biomechanics; viscoelasticity.

Grants and funding

R00 ES025819/ES/NIEHS NIH HHS/United States