Abstract
Background: Our understanding of regional filling of the lung and regional ventilation distribution (VD) is based on studies using radio labelled tracer gases. We aimed to investigate whether these results can be reprduced and differences in regional filling and spatial VD can be detected with electrical impedance tomography (EIT) in adults at different end-expiratory levels (EEL) and tidal volumes (VT).
Methods: EIT measurements were performed in 10 healthy adults in right lateral position. Five different EEL with four different VT at each EEL were tested in random order, resulting in 19 combinations. There were no measurements for the combination of the highest EEL/highest VT as it was not possible to achieve this breathing pattern. EEL and VT were controlled by visual feedback. The fraction of ventilation directed to the right lung (Vright) and the rate of regional filling (right lung vs. total lung) were analysed.
Results: Visual feedback resulted in distinct differences in EEL and VT. Vright increased with increasing EEL and was <0.5 (more air directed to the left lung) only at the lowest EEL (p<0.05). With low EEL the filling of the right lung during the initial phase of the inspiration was slower (p<0.05) and the filling the lungs became more even with increasing EEL. With increasing VT Vright increased significantly (p<0.05) and the filling characteristics changed towards more uneven ventilation.
Conclusion: The effect of different EEL and VT on spatial and temporal VD during spontaneous tidal breathing in right lateral position can be assessed by EIT. Our results are in line with previous studies and suggest that the effect of EEL on ventilation distribution is greater than the effect of VT.
- © 2011 ERS
