E-Mail karger@karger.com Interventional Pulmonology Respiration 2014;88:458–468 DOI: 10.1159/000368086 Lung Ultrasonography May Provide an Indirect Estimation of Lung Porosity and Airspace Geometry Gino Soldati a Andrea Smargiassi b Riccardo Inchingolo b Sara Sher c Rosanna Nenna d Salvatore Valente b Cosimo Damiano Inchingolo d Giuseppe Maria Corbo b a Emergency Medicine Unit, Castelnuovo Garfagnana General Hospital, Lucca, b Pulmonary Medicine Department, University Hospital ‘A. Gemelli’, Rome, c Anesthesia and Intensive Care Unit, Niguarda Cà Granda Hospital, Milan, and d Surgical Pathology Department, ‘L. Bonomo’ General Hospital, Andria, Italy lin solution. Results: Mean volumes of naturally collapsed lungs and fixed expanded lungs were 11.2 ± 0.36 and 44.83 ± 3.03 ml, respectively. Mean densities were 0.622 ± 0.016 and 0.155 ± 0.007 g/ml, respectively. Ultrasound evaluation of collapsed lungs showed dense vertical artifacts and a ‘white lung’ pattern, while the evaluation of expanded lungs showed hyperechoic line and horizontal artifacts of reflec- tion. Histological evaluation showed a different PAS geom- etry in collapsed lungs caused by alveolar size reduction and shape changes with unfolded and closed units modifying the peripheral porosity of the frothy nature of the lung. Con- clusions: Airspace geometry, frothy nature and porosity are the determinants of the different behavior of ultrasound in- teracting with the subpleural lung parenchyma. Chest ultra- sound may thus be interpreted as an indirect ‘estimator’ of lung porosity. © 2014 S. Karger AG, Basel Key Words Chest ultrasound · Lung density · Lung porosity · Sonographic interstitial syndrome · B-lines Abstract Background: Echographic vertical artifacts (B-lines) in chest ultrasonography have often been associated with patho- logical patterns. A scientifically sound explanation of these artifacts has not yet been proposed. Objectives: The ‘spongy’ nature of the lung in its liquid and solid compo- nents and the changes that take place in peripheral airspace (PAS) geometry might be the key point to understanding these phenomena. Methods: Six excised right rabbit lungs were obtained. Each lung underwent direct ultrasound evaluation in two different conditions: at complete tissue elastic recoil volume and at pulmonary expansion volume achieved by applying a constant positive pressure of 12 cm H 2 O. Lung volumes and densities were reported in both conditions. Histological examination was performed on three naturally collapsed lungs and on three lungs under positive pressure inflation after having been fixed in forma- Received: April 27, 2014 Accepted after revision: August 23, 2014 Published online: November 5, 2014 Andrea Smargiassi, MD Pulmonary Medicine Department Università Cattolica del Sacro Cuore Largo Gemelli 8, IT–00168 Rome (Italy) E-Mail smargiassi.a  @  gmail.com © 2014 S. Karger AG, Basel 0025–7931/14/0886–0458$39.50/0 www.karger.com/res G.S., A.S. and R.I. contributed equally to this work. This work was accepted as an abstract at the ERS Congress 2014 in Munich, Germany.