How absolute EIT reflects the dependence of unilateral lung aeration on hyper-gravity and weightlessness?

作者：Hahn G^*; Just A; Hellige G; Dittmar J; Quintel M

来源：Physiological Measurement, 2013, 34(9): 1063-1074.

DOI：10.1088/0967-3334/34/9/1063

• weightlessness
• lung volume
• lung aeration
• lung function
• gravity
• parabolic flights
• electrical impedance tomography
• absolute EIT
• lung impedance
• lung resistivity
• electrical properties of lung tissue
• image reconstruction

We studied the influence of three gravity levels (0, 1 and 1.8 g) on unilateral lung aeration in a left lateral position by the application of absolute electrical impedance tomography. The electrical resistivity of the lung tissue was considered to be a meaningful indicator for lung aeration since changes in resistivity have already been validated in other studies to be proportional to changes in lung volume. Twenty-two healthy volunteers were studied during parabolic flights with three phases of different gravity, each lasting similar to 20-22 s. Spontaneous breathing at normal tidal volume V-T and at increased V-T was performed. During transition to hyper-gravity mean expiratory resistivities (+/- SD in Omega m) increased at normal V-T in the upper (right) lung from 7.6 +/- 1.5 to 8.0 +/- 1.7 and decreased from 5.8 +/- 1.2 to 5.7 +/- 1.2 in the lower ( left) lung. Inspiratory resistivity values are 8.3 +/- 1.6 to 8.8 +/- 1.8 (right) and 6.3 +/- 1.3 to 6.0 +/- 1.3 (left). At increased V-T, the changes in resistivities at end-expiration were 7.7 +/- 1.5 to 8.0 +/- 1.7 (right) and 5.8 +/- 1.2 to 5.7 +/- 1.2 (left). Corresponding end-inspiratory values are 9.9 +/- 1.9 to 10.0 +/- 2.0 (right) and 8.6 +/- 2.1 to 7.9 +/- 2.0 (left). During weightlessness, the distortion in the lungs disappeared and both lungs showed a nearly identical aeration, which was between the levels displayed at normal gravity. The small increase in resistivity for the upper lung during transition to hyper-gravity from 1 to 1.8 g at increased V-T suggests that the degressive part of the pressure-volume curve has already been reached at end-inspiration. The results for a left lateral position are in agreement with West%26apos;s lung model which has been introduced for cranio-caudal gravity dependence in the lungs.

• 出版日期2013-9