Acta anaesthesiologica Scandinavica, 2011-02, Vol.55 (2), p.157-164
Background: Continuous positive airway pressure (CPAP) has been shown to improve oxygenation and a number of different CPAP systems are available. The aim of this study was to assess lung volume and ventilation distribution using three different CPAP techniques.
Methods: A high‐flow CPAP system (HF‐CPAP), an ejector‐driven system (E‐CPAP) and CPAP using a Servo 300 ventilator (V‐CPAP) were randomly applied at 0, 5 and 10 cmH2O in 14 volunteers. End‐expiratory lung volume (EELV) was measured by N2 dilution at baseline; changes in EELV and tidal volume distribution were assessed by electric impedance tomography.
Results: Higher end‐expiratory and mean airway pressures were found using the E‐CPAP vs. the HF‐CPAP and the V‐CPAP system (P〈0.01). EELV increased markedly from baseline, 0 cmH2O, with increased CPAP levels: 1110±380, 1620±520 and 1130±350 ml for HF‐, E‐ and V‐CPAP, respectively, at 10 cmH2O. A larger fraction of the increase in EELV occurred for all systems in ventral compared with dorsal regions (P〈0.01). In contrast, tidal ventilation was increasingly directed toward dorsal regions with increasing CPAP levels (P〈0.01). The increase in EELV as well as the tidal volume redistribution were more pronounced with the E‐CPAP system as compared with both the HF‐CPAP and the V‐CPAP systems (P〈0.05) at 10 cmH2O.
Conclusion: EELV increased more in ventral regions with increasing CPAP levels, independent of systems, leading to a redistribution of tidal ventilation toward dorsal regions. Different CPAP systems resulted in different airway pressure profiles, which may result in different lung volume expansion and tidal volume distribution.
Biological and medical sciences ; Anesthesia ; Medical sciences ; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy ; Expiratory Reserve Volume - physiology ; Humans ; Middle Aged ; Air Pressure ; Male ; Electric Impedance ; Tidal Volume ; Nitrogen ; Continuous Positive Airway Pressure - instrumentation ; Adult ; Female ; Supine Position - physiology ; Respiratory Mechanics - physiology ; Continuous positive airway pressure ; Index Medicus ; Continuous Positive Airway Pressure ; Expiratory Reserve Volume ; physiology ; Anestesi och intensivvård ; Anesthesiology and Intensive Care ; diagnostic use ; instrumentation ; Respiratory Mechanics ; Supine Position
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