Determination of Normal Values of Regional Pulmonary Strain Using a New Ultrasonographic Tool in Healthy Volunteers

Participants will have their functional residual capacity (FRC) measured by a nitrogen dilution technique. Subsequently, they will be instructed to breathe 8 different inspired volumes (5 to 15 ml/kg predicted body weight). Tidal volumes will be measured using a spirometer. For each inspired volume, 3 respiratory cycles will be recorded at 15 predetermined anatomic sites: 1st and 3rd left and right intercostal spaces at the mid-clavicular line, 5th right intercostal space at the mid-clavicular line, 2nd, 4th and 6th left and right intercostal spaces at the anterior axillary line, and 5th and 7th left intercostal spaces and right to the posterior axillary line. For each image, the probe will be oriented perpendicularly to the ribs. A research, non-commercially available, non-invasive vascular elastography platform will be used to calculate the various strain parameters for all of the recorded cineloops. For each recorded clip, an experienced lung ultrasonographer will segment the pleura on a single reference image. From this image, an algorithm will define a region of interest which will be tracked throughout the rest of the images of the video sequence. Finally, the algorithm will calculate the various components of pleural strain.