Automated full-range pressure-volume curves in mice and rats

Abstract

Pressure-volume (PV) curves constructed over the entire lung volume range can reliably detect functional changes in mouse models of lung diseases. In the present study, we constructed full-range PV curves in healthy and elastase-treated mice using either a classic manually operated technique or an automated approach using a computer-controlled piston ventilator [flexiVent FX; Scientific Respiratory Equipment (SCIREQ), Montreal, Quebec, Canada]. On the day of the experiment, subjects were anesthetized, tracheotomized, and mechanically ventilated. Following an initial respiratory mechanics scan and degassing of the lungs with 100% O, full-range PV curves were constructed using either the classic or the automated technique. In control mice, superimposable curves were obtained, and statistical equivalence was attained between the two methodologies. In the elastase-treated ones, where significant changes in respiratory mechanics and lung volumes were expected, very small differences were observed between the two techniques, and the criteria for statistical equivalence were met in two out of four parameters assessed. The automated technique was adapted to rats and used to estimate the functional residual capacity (FRC) by volume subtraction. This novel approach generated FRC estimates consistent with the literature, with added accuracy relative to the existing method in diseased subjects. In conclusion, the automated technique generated full-range PV curves that were equivalent or very close to those obtained with the classic method under physiological or severe pathological conditions. The automation facilitated some technical aspects of the procedure, eased its use across species, and helped derive a more accurate estimate of FRC in preclinical models of respiratory disease. Partial and full-range pressure-volume (PV) curves are frequently used to characterize lung disease models. Whereas automated techniques exist to construct partial PV curves, a manually operated approach is classically employed to build the full-range ones. In this study, the full-range PV curve technique was automated using a computer-controlled piston ventilator. The automation simplified the technique, facilitated its extension to other species, and inspired a novel way of estimating the functional residual capacity in laboratory rodents.

Assessment of Respiratory Function in Conscious Mice by Double-chamber Plethysmography

“…If the study involves repeated evaluations over time, repeat the whole measurement sequence at each chosen timepoint. Note: It is wisely recommended to complement the study with some precise measurements of respiratory mechanics and/or lung volumes 1 15 .…”

“…Under such conditions, where the animal's natural physiological state is unaltered, it is thus impossible to discern whether a change in sRaw stems from an alteration in airway resistance, from a change in TGV, or from a mix of the two. Hence, it is recommended to complement the DCP evaluation with more invasive measurements of respiratory mechanics and/or lung volumes, such as those provided by the FOT 1 15 .…”

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

“…COVID-19 has risen to be one of the biggest killers of 2020, which resulted in 5,817,385 confirmed cases and 362,705 deaths through May 30, 2020 (Stokes et al, 2020). Pulmonary diseases impact tissue structure (Eskandari et al, 2013;Burgstaller et al, 2017;Copot et al, 2017), which in turn modifies respiratory mechanics (Faffe and Zin, 2009;Eskandari et al, 2018) in terms of conducting lung volumes (Broussard et al, 2006;Brown et al, 2006;Limjunyawong et al, 2015a,b;Robichaud et al, 2017), mechanical and viscoelastic properties (Bates et al, 2007;Suki and Bates, 2011) and air flow distribution in the lung (Rouby et al, 2003;Grasso et al, 2008). Understanding each of these changes and how they differ in healthy and diseased patients is necessary to advance diagnosis and treatment strategies in lung disease (Sattari and Eskandari, 2020).…”

“…Changes in conducting lung volumes have been used as an indicator for detecting functional changes due to disease emergence, such as fibrosis and asthma (Broussard et al, 2006;Brown et al, 2006;Limjunyawong et al, 2015a,b;Robichaud et al, 2017). Increasingly, whole lung organ displacementloading tests, measured as volumes and pressures resulting from inflation and deflation, are used to assess lung behavior.…”

Modelling the Impact of Chronic Cigarette Smoke Exposure in Obese Mice: Metabolic, Pulmonary, Intestinal, and Cardiac Issues

“…Next, the mechanical properties of the mouse respiratory system were assessed at baseline, i.e., before the construction of a full-range pressure-volume (PV) curve. This was done using a sequence of measurements integrated by default in the flexiVent operating software and referred to as the mouse mechanics scan [25]. The area between the PV loop inflation and deflation limbs (Hysteresis) was then calculated.…”