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H. Heinze, B. Sedemund-Adib, U. W. Gosch, W. Eichler
Department of Anaesthesiology, University of Luebeck, Luebeck, Germany
[Applied Cardiopulmonary Pathophysiology 12: 27-32, 2008]
Abstract
Background: Monitoring of functional residual capacity (FRC) may help detecting alveolar derecruitment and guiding countermeasures like recruitment maneuvers. The aim of this study was to detect the possible decrease of FRC after a suctioning procedure - indicating alveolar derecruitment - and the effect of a successful alveolar recruitment maneuver on pulmonary function.
Methods: We studied 20 postoperative mechanically ventilated cardiac surgery patients. FRC was assessed by oxygen washout using a sidestream O2-analyser (LUFU system (Dräger Medical AG, Luebeck, Germany)). FRC, respiratory compliance, paO2/FiO2 (PF-ratio) and paCO2 were recorded at baseline, after a standard suctioning procedure with disconnection of the ventilator (20 sec, 14 F catheter, 200 mmHg negative pressure) (post ETS), and after a standard recruitment manoeuvre (PEEP 15 mbar, PIP 35–40 mbar for 30 sec) (post RM).
Results: Mean FRC decreased post ETS (3.2 L ± 1.2) compared to baseline (3.4 L ± 1.1, p = 0.046) and increased post RM compared to post ETS (3.5 L ± 1.0, p=0.039). Mean respiratory compliance showed no significant changes. paCO2 decreased and PF-ratio increased post RM compared to post ETS (p = 0.005, p = 0.026, respectively). Relative FRC changes post ETS correlated to changes of PF-ratio post RM (Pearson: -0.896, p<0.001).
Conclusion: In post cardiac surgery patients changes of FRC after alveolar de- and recruitment can be detected at bedside using the oxygen washout technique. There was a strong association of a FRC-decrease after open ETS with an improvement of oxygenation from a consecutive RM. A FRC decrease may help to identify those patients who profited from a RM in terms of increased oxygenation, even in absence of blood gas data.
Key words: functional residual capacity, lung volume measurement, mechanical ventilation, alveolar derecruitment, lung recruitment, acute lung injury, critical care
Address for corresponding: Hermann Heinze, M.D., Department of Anaesthesiology, University of Luebeck, Ratzeburger Allee 160, D-23538 Luebeck, Germany, E-Mail:  Hermannheinze@bitte-keinen-spamngi.de
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