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Lung volume and ventilation distribution changes by positioning and application of positive airway pressure in healthy subjects

Angela Freydag1, Jan Karsten2, Torsten Meier3, Hermann Heinze1
1 Department of Anaesthesiology and Intensive Care, University of Luebeck, Luebeck, Germany
2 Department of Anaesthesiology and Intensive Care, Hannover Medical School, Hannover, Germany
3 Department of Anaesthesiology and Intensive Care,  Brüderkrankenhaus St. Josef, Paderborn, Germany
[Applied Cardiopulmonary Pathophysiology 17: 267-274, 2013]


Background: Noninvasive continuous positive airway pressure (CPAP) is used to improve functional residual capacity (FRC) and ventilation distribution. The aim of this study was to evaluate whether a reduced FRC would be restored by noninvasive CPAP and if this resulted in ventilation distribution changes.
Methods: We investigated 22 subjects. Measurements were made sitting and supine without CPAP and supine with a CPAP of 7cmH2O. FRC was measured with the oxygen washin-washout method. Ventilation distribution was recorded with electrical impedance tomography.
Results: FRC was reduced by 16% from the sitting to the supine position. Ventilation distribution showed a trend to ventral lung regions. In the supine position, application of CPAP increased the FRC but did not change the ventilation distribution.
Conclusion: Noninvasive CPAP restores a reduced FRC in healthy subjects, but does not change ventilation distribution. This may have an impact on the optimization of noninvasive ventilation in patients.

Key words: Alveolar Recruitment, Electrical Impedance Tomography, Functional Residual Capacity, Lung Volume Measurement, Noninvasive Ventilation, Ventilation Monitoring

Correspondence address:
Dr. Angela Freydag
Department of Anaesthesiology
University of Luebeck
Ratzeburger Allee 160
23538 Luebeck
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