Application Note | ElastoSens™ Bio
Measuring mechanical properties of lung tissue using ElastoSens™ Bio
Introduction
The lungs are highly specialized organs whose mechanical behavior underlies their ability to sustain gas exchange. Properties such as elasticity, stiffness, and compliance determine how easily the lungs expand and recoil during breathing, while viscoelasticity reflects their capacity to store and dissipate energy with each cycle. These characteristics are not static; they vary with developmental stage, environmental exposures, and disease progression. By studying them, scientists and clinicians can better understand how healthy lungs function, detect early signs of pulmonary disorders, and design therapies that restore or preserve performance.
Key mechanical properties of lung tissue
Elasticity
Elasticity describes the ability of lung tissue to return to its original shape after being stretched during inhalation. It is fundamental for efficient ventilation, as it allows the lungs to recoil and support exhalation without excessive muscular effort.
Compliance
Compliance refers to how easily the lungs can expand when subjected to pressure changes. It reflects the balance between tissue elasticity and surface tension within the alveoli. Healthy lungs maintain high compliance, ensuring low work of breathing.
Stiffness
Stiffness is the resistance of lung tissue to deformation. An increase in stiffness alters the mechanical load on the respiratory muscles and impairs lung expansion, often signaling tissue remodeling or fibrosis.
Viscoelasticity
Viscoelasticity combines elastic recoil with time-dependent energy dissipation. This property helps buffer the lungs against mechanical stresses from repetitive cycles of breathing, ensuring resilience under physiological and pathological conditions.
Relationship between diseases and mechanical properties of lung tissue
Pulmonary Fibrosis
Pulmonary fibrosis leads to excessive deposition of extracellular matrix proteins, which markedly increase tissue stiffness. This change reduces compliance and contributes to impaired ventilation and gas exchange.
Chronic Obstructive Pulmonary Disease (COPD)
In COPD, progressive tissue degradation and remodeling reduce elasticity and alter compliance. These changes compromise the ability of the lungs to recoil during exhalation, leading to air trapping and reduced respiratory efficiency.
Pulmonary Hypertension
Pulmonary hypertension affects the mechanics of both vascular and parenchymal compartments. Increased vascular stiffness and altered tissue viscoelasticity place additional load on the right ventricle and compromise gas exchange efficiency.
How lung tissue mechanics are assessed
In Vivo techniques (Clinics)
In the clinic, lung mechanical properties are often assessed through spirometry and body plethysmography, which provide information on lung volumes and airway resistance. To probe deeper, the Forced Oscillation Technique (FOT) applies oscillatory pressure waves during normal breathing to measure respiratory system impedance, separating airway resistance from tissue elastance. These tests are non-invasive and increasingly used to detect subtle changes in lung mechanics. Imaging-based approaches, such as computed tomography (CT) and magnetic resonance imaging (MRI), are also emerging as powerful methods to couple structural and functional measurements of the lungs.
Ex Vivo techniques (Research)
In research, ex vivo measurements allow controlled studies of lung biomechanics outside the body. Pressure–volume (P–V) curve analysis is a classical method to determine compliance and elastance by inflating and deflating isolated lungs. The Forced Oscillation Technique (FOT) can also be applied to excised lungs to quantify resistance and reactance independent of chest wall effects. At the tissue level, strip tests, indentation, and microscopy-based methods provide insight into local stiffness and viscoelasticity of parenchymal samples. These ex vivo approaches yield precise data but necessarily remove the lungs from their physiological environment, which can limit translation to in vivo function.
Case study: Lung tissue mechanical characterization with ElastoSens™ Bio
ElastoSens™ Bio: a contactless tool for Ex Vivo tissue testing
In the field of lung biomechanics, the ElastoSens™ Bio offers an innovative solution for ex vivo testing. This instrument enables continuous and non-destructive measurement of viscoelastic properties, ensuring that lung tissue samples remain intact throughout the experiments. Its technology allows for precise characterization of soft biological tissues and supports repeated testing over time under different environmental conditions, thereby complementing and extending the insights provided by conventional mechanical assays.
To demonstrate the capabilities of the ElastoSens™ Bio, we performed an ex vivo study using lung tissue specimens. The following section describes the materials and methods applied in this experiment, followed by the results, highlighting a practical example of the instrument’s application.
Material and methods
Lungs from pork and sheep were obtained from a local farm. Specimens with an approximate cylindrical form (23 mm internal diameter, variable height) were cut using a biopsy-like punch. Each was carefully positioned in the macro holder of the ElastoSens™ Bio instrument and measured at room temperature for one minute.
Real-time viscoelastic data were acquired, including the shear storage modulus (G′) and damping ratio (Tan𝛿). For each experimental condition, values correspond to the average of five distinct specimens, sampled from the same anatomical location in five separate lungs (n=5).
Figure 1. Lung tissue sample.
Results and discussion
The viscoelastic properties of lung tissue were evaluated using the ElastoSens™ Bio testing system (Figure 2). Pig lung tissue showed a shear storage modulus (G′ = 2.78 ± 0.43 kPa) compared to 2.28 ± 0.69 kPa for sheep lung tissue. Sheep lung, however, exhibited a slightly higher damping ratio (Tan δ = 0.38 ± 0.08 vs. 0.30 ± 0.04), reflecting a greater contribution of viscous energy dissipation. These results suggest that pig lung tissue tends to be mechanically stiffer, while sheep lung tissue demonstrates a more dissipative response.
For comparison, small-amplitude oscillatory shear testing of porcine lungs reported G′ ≈ 3.3 ± 0.5 kPa (Polio et al., 2018), which is in close agreement with the ElastoSens™ Bio measurement. The ElastoSens™ Bio captures physiologically representative lung stiffness while enabling non-destructive and repeatable testing.
Figure 2: Viscoelastic properties of lung tissue for sheep and pig: shear storage modulus (G′) (left) and damping ratio (Tan𝛿) (right) obtained with the ElastoSens™ Bio non-destructive testing system (mean ± SD, n=5).
Conclusions and perspectives
Elasticity, stiffness, viscoelasticity, and anisotropy are defining properties of lung tissue, central to both normal respiratory mechanics and disease-related remodeling. This study demonstrates that non-destructive testing with the ElastoSens™ Bio allows accurate characterization of lung mechanics, with continuous monitoring of shear storage modulus (G′) and damping ratio (Tan𝛿). The technique ensures precise, reproducible outcomes, providing a solid foundation for comparative research across conditions and species.
In addition, the ElastoSens™ Bio provides unique advantages for pulmonary and biomaterials research:
- Simple preparation and setup minimize handling and preserve lung tissue hydration and delicate alveolar architecture.
- High sensitivity and repeatability allow consistent measurements across different lung regions (upper, middle, and lower lobes), capturing intra-organ variability.
- Cross-species benchmarking facilitates translational research by directly comparing lung mechanics in animal models and humans.
- Platform versatility supports testing of diverse soft tissues and biomaterials under identical conditions, useful for developing pulmonary implants, scaffolds, or adhesives.
- Engineered tissue applications benefit from non-destructive, repeated measurements that reflect the dynamic evolution of bioengineered lung constructs.
- Controlled incubation and repeated testing make it possible to monitor changes in viscoelastic properties over time, whether due to ventilation, pharmacological intervention, or disease progression.
Altogether, these strengths position the ElastoSens™ Bio as a valuable resource for lung tissue research, translational physiology, and biomaterial development.
References
Ahookhosh, K., Vanoirbeek, J., & Vande Velde, G. (2023). Lung function measurements in preclinical research: What has been done and where is it headed?. Frontiers in Physiology, 14, 1130096.
Neelakantan, S., Xin, Y., Gaver, D. P., Cereda, M., Rizi, R., Smith, B. J., & Avazmohammadi, R. (2022). Computational lung modelling in respiratory medicine. Journal of The Royal Society Interface, 19(191), 20220062.
Polio, S. R., Kundu, A. N., Dougan, C. E., Birch, N. P., Aurian-Blajeni, D. E., Schiffman, J. D., & Peyton, S. R. (2018). Cross-platform mechanical characterization of lung tissue. Journal of Biomechanics, 79, 97–103.
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