The distribution of lung ventilation of healthy subjects placed in various positions, by the method of impedance tomography

Abstract

Impedance tomography is a modern method for real time monitoring of the air distribution during lung ventilation, as it can record the changes of lung impedance during breathing and via a mathematical processing creates a visual image representing the changes of lung ventilation. The aim of this study is to record the percentage distribution of lung ventilation in healthy subjects, in several positions. The results of this study can be used for explaining the fluctuations of oxygenation in cases such as bronchial drainage or for the interpretation of pulmonary ventilation in pathological cases such as scoliosis. Eight young, non-smoking, healthy volunteers, without a previous respiratory disease, were monitored by impedance tomography. They were placed in the following positions: Sitting, Supine, Trendelenburg, Right Side Lying, Left Side Lying, Prone, Semi-Fowler's position 30°, Semi-Fowler's position 45°, Right Trunk Rotation and Left Trunk Rotation. The recorded data were used to compare the percentage of the air distribution between the anterior and posterior thoracic segment and between same lung (right or left) of each object in each position. The anterior-posterior percentage of the air distribution during lung ventilation did not show any remarkable changes in any position and in any angle of head elevation of the bed, while statistically significant differences were detected comparing the percentage of the air distribution in each lung on the lateral decubitus positions and on the trunk rotations (mean ± SD: 9 ± 3.85 P ≤ 0.001, 9.25 ± 4.73 P = 0.001, respectively). In normal healthy young individuals, head elevation of the bed does not have any impact on the regional lung ventilation. On the contrary the side lying positions seems to favor the dependent lung and the trunk rotation appears to compress the same to the rotation side lung, with a significant impact on its ventilation.