Gravity effects on regional lung ventilation determined by functional EIT during parabolic flights

Abstract

Gravity-dependent changes of regional lung function were studied during normogravity, hypergravity, and microgravity induced by parabolic flights. Seven healthy subjects were followed in the right lateral and supine postures during tidal breathing, forced vital capacity, and slow expiratory vital capacity maneuvers. Regional 1) lung ventilation, 2) lung volumes, and 3) lung emptying behavior were studied in a transverse thoracic plane by functional electrical impedance tomography (EIT). The results showed gravity-dependent changes of regional lung ventilation parameters. A significant effect of gravity on regional functional residual capacity with a rapid lung volume redistribution during the gravity transition phases was established. The most homogeneous functional residual capacity distribution was found at microgravity. During vital capacity and forced vital capacity in the right lateral posture, the decrease in lung volume on expiration was larger in the right lung region at all gravity phases. During tidal breathing, the differences in ventilation magnitudes between the right and left lung regions were not significant in either posture or gravity phase. A significant nonlinearity of lung emptying was determined at normogravity and hypergravity. The pattern of lung emptying was homogeneous during microgravity.

Distribution of lung ventilation in spontaneously breathing neonates lying in different body positions

“…Thanks to the excellent time resolution EIT is able to determine not only the local magnitude of lung ventilation and local resting volume (e.g. [6,7]) but also the dynamics of local filling and emptying of lung units [8]. In view of these EIT features in monitoring local lung function, it is expected that EIT may be useful in the assessment of the efficacy of therapeutic interventions, including mechanical ventilation, and in the prediction of the progress of acute and chronic lung disease.…”

Developing Customized Evaluation Software for Clinical Trials: An Example with Obstructive Lung Diseases

“…EIT images showing time-difference impedance distribution within measuring layer are reconstructed based on the voltage measurement. Applications of EIT have been proposed to assess the ventilation distribution or guiding respiratory therapies in subjects without lung disease [5,6] and in patients with mild, moderate, and severe lung diseases [7][8][9]. However, evaluation of EIT measurement is not easy for doctors since 1) there is no established guideline for measurement; 2) commercially available software is device specific and rarely extensible for various clinical trials; 3) open source software is comprehensive but not disease specific.…”

Electrical Impedance Tomography in Acute Respiratory Distress Syndrome

“…A CT scan acquired in the same chest plane is shown for comparison. Using the described approach of quantifying the ventilation-related changes in electrical impedance, functional EIT imaging is capable of characterising the distribution of ventilation in the chest cross-section under a variety of conditions (spontaneous breathing, artificial ventilation, healthy lungs or lung pathology) [19,[23][24][25][26][27][28][29][30][31] (see also Fig. 3, the upper scans).…”

“…Pathological changes in lung electrical impedance resulting, e.g., from acute lung injury or lung collapse can also be visualised using this approach [25,35,36]. Further types of functional EIT scans aiming at the visualisation of the dynamics of regional lung emptying and filling have also been published [28,37,38].…”

“…It has also been shown that regional time courses of the EIT signal may characterise the nonlinearity of regional filling and emptying of lung regions [28] which in mechanically ventilated patients may be a sign of lung overdistension or collapse [37]. A downward curvilinearity of the regional EIT signal may result from lung overdistension whereas an upward curvilinearity may indicate recruitment.…”