Lung disease changes more than airflow. It can also change how the whole organ inflates, relaxes, and distributes pressure during breathing. That is part of what makes lung volume pressure testing so useful in research. It gives investigators a way to look at whole-lung mechanical behaviour rather than relying only on airflow-based readouts.

In this project, Prof. Mona Eskandari’s group at UC Riverside partnered with CellScale to build a custom system for measuring whole-lung volume and pressure during inflation and deflation. You can read the resulting peer-reviewed publication in Frontiers in Bioengineering & Biotechnology.

The result was a software-controlled device designed to capture continuous volume-pressure curves, support studies of lung viscoelasticity, and allow direct comparisons between positive- and negative-pressure ventilation.

Why airflow is not the same as lung volume

One of the key ideas behind this lung volume pressure testing system is that air pushed into the lung is not always the same as the true change in lung volume. In a heterogeneous organ, pressure distribution is not uniform, and some of the applied air volume is affected by compressibility rather than becoming actual tissue expansion. That makes direct flow measurements incomplete if the goal is to understand whole-lung mechanics.

To get around that problem, the lungs were placed inside a sealed chamber. As the lung expanded, it displaced volume inside the chamber, and the displaced volume needed to maintain atmospheric pressure in the tank became the true measure of lung volume change. That was a major advantage of the design, because it allowed the system to account for air compressibility in real time instead of relying on a manual correction step.

This is what makes the setup more than a simple inflation device. It is a whole-organ pressure-volume mechanical testing system built to measure how lungs actually deform under controlled loading.

Measuring whole-lung viscoelasticity

The device is a custom-designed lung volume pressure testing machine for measuring whole lung organ viscoelasticity and comparing positive- and negative-pressure ventilation. The system was built to construct standardized continuous volume-pressure curves, record pressure-time behaviour, and evaluate rate-dependent and time-dependent responses at the organ scale.

That matters because lungs are not purely elastic. They show hysteresis, preconditioning effects, and stress relaxation. In the study, those features were demonstrated by comparing mouse lungs with an elastic balloon. The balloon behaved as expected for a more elastic material, while the mouse lungs showed pressure relaxation, volume dependence, rate dependence, and preconditioning sensitivity. The figures on pages 5 through 8 show those differences clearly, including the greater hysteresis and pressure relaxation seen in the lung specimens.

If you want more background on time-dependent mechanical behaviour in soft tissues, see our page on Viscoelastic & Time-Dependent Testing.

A custom system for mice and pigs

Another challenge in this project was scale. Mouse lungs operate in the millilitre range, while pig lungs inflate by litres. The team therefore built two separate systems: a smaller platform for murine and rat lungs and a larger one for porcine and human-scale testing. The paper states that the maximum inflation capacities were 3 mL for the mouse system and 3 L for the pig system, with much higher inflation-deflation rates required for the larger device.

This scaling work is one of the most practical parts of the project. It shows that the custom solution was not just a lab prototype for one specimen size. It was designed as a family of tools for whole-lung research across very different experimental models.

For a broader look at related application areas, see our page on Lung & Pleural Tissue Biomechanics.

Why volume-control improves lung research

Traditional lung inflation tests often use pressure-controlled methods. The paper explains why that can be limiting. Previous systems typically required either a known starting lung volume or degassing of the lung before testing. Degassing can collapse alveoli and make reopening pressures artificially high, while variation in starting conditions makes comparisons between studies harder.

The custom CellScale lung volume pressure testing system instead used volume control with measured pressure and a defined preload state. That allowed the authors to generate standardized volume-pressure curves without the need for pulmonary degassing. According to the study, this improved reproducibility and reduced experimental challenges while also opening the door to new whole-organ viscoelastic measurements.

The value of the system is not just inflation and deflation. It is controlled volume input paired with continuous pressure measurement and real-time correction for compressibility.

Positive- and negative-pressure ventilation in one platform

One of the more distinctive features of the system was its ability to compare artificial positive-pressure ventilation with physiologic negative-pressure ventilation. The machine did this by reversing the software control roles of the two pistons. In one mode, air was pushed into the specimen. In the other, the tank volume changed to create a pressure drop that pulled the specimen open.

The paper shows that for the same applied volume, the absolute pressure changes were not drastically different between positive- and negative-pressure modes, but the resulting compressed air volume of the specimen could differ by more than 1 L in the bladder demonstration. That suggests meaningful differences in local tissue strains even when the nominal applied volume is the same. The pressure-time plots on page 9 illustrate this comparison directly.

That is especially relevant for pulmonary research, because the authors note that heterogeneous airflow distribution and altered effective lung volume are important in diseased lungs and may behave differently under positive- and negative-pressure ventilation.

Why this matters for pulmonary biomechanics

This project sits at the intersection of pulmonary biomechanics, custom instrumentation, and translational research. Diseases such as asthma, emphysema, fibrosis, and COVID-related lung injury can change conducting lung volumes, tissue viscoelasticity, and airflow distribution. A system that measures whole-lung pressure-volume response under controlled conditions helps researchers study those changes more directly.

It also creates a path toward better ventilator research. The paper explicitly notes that these methods can support future studies of viscoelasticity as a biomarker and improvements to patient ventilators through direct comparisons of positive- and negative-pressure mechanics.

If you want to explore the testing side of pressure-driven protocols more broadly, visit our page on Hydrostatic Pressure Testing.

Custom solutions for your research

This is a good example of the kind of problem that standard equipment does not always solve well. The team needed a system that could:

measure true lung volume change rather than just applied air volume
maintain a controlled pressure state in a sealed chamber
support both small and large specimen scales
capture pressure-time and volume-pressure behaviour continuously
compare positive- and negative-pressure mechanics in the same overall framework

That combination is exactly why a custom solution made sense here.

To learn more about how CellScale supports specialized biomechanical system design, visit our Custom Solutions page.

Read the full case study

This blog is really the short version of a much deeper custom build story. For the full project background, device concept, and application details, readers should continue to the Active Pressure/Volume Control for Lung Research case study.

The full publication describing this project is: Introducing a Custom-Designed Volume-Pressure Machine for Novel Measurements of Whole Lung Organ Viscoelasticity and Direct Comparisons Between Positive- and Negative-Pressure Ventilation.