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Assessing the Airway Contribution to Total Respiratory Compliance

Being distensible, the airways contribute to the total compliance of the respiratory system and, over the last 50 years or so, researchers have had an interest in establishing their specific contribution ([1]).  Indeed, the airway diameter as well as the volume of air available for ventilation following inspiration can both be affected by a change in the distensibility of the airways. As a result, stiff airways could mean more effort to inhale, while compliant airways could lead to expiratory flow limitation from a susceptibility to collapse.

In mice, a species frequently used in preclinical models of respiratory diseases, the development of a direct and accessible measurement technique for the determination airway compliance (Caw) has been hampered by the ability to record pressure and volume signals pertaining only to the airways in small size subjects.

In a recent scientific article ([1]), consideration was given to the inflation limb of a full-range pressure-volume (PV) curve (Figure 1), a maneuver readily available in the flexiVent system ([2]).  Full-range PV curves are typically used to assess the static compliance of the respiratory system as well as lung volumes such as the total lung capacity (TLC) or the residual volume (RV).  However, as the maneuver starts following a degassing of the lungs, its initial portion contains a segment, prior to the opening of the collapsed lung parenchymal tissue, where only the airway tree is inflated.

The study evaluated the feasibility of using that initial PV inflation segment for the determination of Caw. The approach was applied to full-range PV curves from three mouse models of respiratory diseases and the results highlighted its ability to detect disease-related changes (2).

The introduction of an accessible methodology to quantitate airway compliance in mice contributes to expand the information available from disease models, which could provide a new insight on the physiological or pathophysiological underlying mechanisms.

The airways supply the lung air spaces, or alveoli, and variations in their compliance can influence lung function. For more information on airway compliance measurements or on comprehensive and detailed assessments of the respiratory function using the flexiVent, please contact us.

References

[1] Mead J. Contribution of compliance of airways to frequency-dependent behavior of lungs. J Appl Physiol 26: 670-673, 1969.  https://doi.org/10.1152/jappl.1969.26.5.670.

[2] Robichaud A. et al. Airway Compliance Measurements in Mouse Models of Respiratory Diseases. Am J Physiol -Lung Cell Mol Physiol 321: L204-L212, 2021.  https://doi.org/10.1152/ajplung.00470.2020.

[3] Robichaud A. et al. Automated full-range pressure-volume curves in mice and rats. J Appl Physiol 123: 746-756, 2017.  https://doi.org/10.1152/japplphysiol.00856.2016.

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