Abstract
Background: Interaction of ultrasounds with aerated peripheral lung parenchyma can determine echographic artifactual vertical phenomena, often associated to pathological patterns. A fine scientific explanation of these artefacts hasn't been yet proposed. The “spongy” nature of the lung in its liquid and dry components might be the key point to understand these phenomena in case of changing of superficial density and porosity.
Methods: Six excised right lungs were obtained from 6 white rabbits. Each lung underwent directly ultrasound (US) evaluation in two different condition: at complete tissue elastic recoil and at pulmonary expansion achieved by applying a constant positive pressure(12 cmH2O) through the bronchial lumen. Lung volumes and densities were reported in both conditions. Histological examination was performed after fixing in formalin solution 3 lungs while applying positive pressure and 3 lungs naturally collapsed.
Results: Mean volumes of collapsed and expanded lungs were 10.6±0.4 and 47±5mL respectively (p<0.001). Mean densities were 0.64±0.05 and 0.15±0.02g/mL respectively (p<0.001). US evaluation of collapsed lungs showed dense vertical artefacts and “white lung”. US evaluation of expanded lungs showed hyperechoic line and horizontal artefacts of reflection. Histological evaluation showed different peripheral airspaces geometry in collapsed ones caused by alveolar size reduction and shape changes with unfolded and closed units modifying peripheral porosity of the frothy nature of lung.
Conclusions:Airspace geometry, frothy nature and porosity are determinants of the different behaviour of US interacting with the peripheral lung parenchyma. Lung US may be interpreted as indirect “estimator” of lung porosity.
- © 2014 ERS