Comparison of monitoring performance of Bioreactance vs. pulse contour during lung recruitment maneuvers.

INTRODUCTION: This study was designed to test the hypothesis of equivalence in cardiac output (CO) and stroke volume (SV) monitoring capabilities of two devices: non invasive transthoracic bioreactance (NICOM), and a pulse contour analysis (PICCO PC) coupled to transpulmonary thermodilution (PICCO TD).

METHODS: We included consecutive patients of a single ICU following cardiac surgery. Continuous minute-by-minute hemodynamic variables obtained from NICOM and PICCO PC were recorded and compared in 20 patients at baseline, during a lung recruitment maneuver (20 cmH2O of PEEP) and following withdrawal of PEEP. PICCO TD measurements were also determined. We evaluated the accuracy of these two technologies at baseline using PICCO TD as reference and we estimated the precision by the fluctuation around the mean value (2SD/mean). Then, we assessed time response, amplitude response and reliability for detecting expected decreases when PEEP was applied. Type I and type II errors were analyzed.

RESULTS: CO values (PICCO TD) ranged from 1.6 to 8.0 L.min-1. At baseline, CO values were comparable for NICOM, PICCO PC and PICCO TD: 5.0 +/- 1.2, 4.7 +/- 1.4 and 4.6 +/- 1.3 L.min.-1, respectively (NS). Limits of agreements with PICCO TD were 1.52 L.min.-1 for NICOM and 1.77 L.min.-1 for PICCO PC, NS. The 95% statistical power gives an equivalence with a threshold of 0.52 L.min.-1 for NICOM vs. PICCO PC. The CO precision was 6 +/- 3% and 6 +/- 5% for NICOM and PICCO PC, respectively, NS. When PEEP was applied, CO was reduced by 33 +/- 12%, 31 +/- 14% and 32 +/- 13%, for NICOM, PICCO PC and PICCO TD, respectively (NS). Time response was 3.2 +/- 0.7 minute for NICOM vs. 2 +/- 0.5 minute for PICCO PC (NS). SV results were comparable to those for CO.

CONCLUSIONS: Although limited to 20 patients, this study has enough power to show comparable CO and SV monitoring capabilities of Bioreactance and pulse contour analysis calibrated by transpulmonary thermodilution.