Offline, on high-resolution paper tracings, including airway and blood pressure waveforms and after their numerical enlargement, ��RESPPP was calculated by an observer blinded to other hemodynamic data as follows and averaged over three consecutive respiratory cycles:within one respiratory cycle [1]. Other indices derived www.selleckchem.com/products/MG132.html from respiratory changes in arterial pressure were calculated over three consecutive respiratory cycles: the expiratory decrease in systolic pressure (dDown) and the respiratory changes in systolic pressure (SPV) [15].Echocardiography was performed within 6 hours of measurements to quantify valvular regurgitations and to detect intracardiac shunts or acute cor pulmonale (right-to-left ventricular end-diastolic area ratio above 0.6 with paradoxical septal wall motion).

Statistical analysisPatients were classified as responders if volume expansion induced an increase in CO ��10% and as nonresponders otherwise. Indeed, a measured increase of CO above 9% (which we rounded to 10%) reliably reflects that a real change has taken place [22]. To validate this choice of cutoff in our patients (assessment of intermeasurement variability within each set of measurements), we calculated the least significant change (LSC) for each set of CO measurements in each patient at each phase ((1.96��2)CV/��number of measurements within one set) with CV being the coefficient of variation (SD/mean). Thus, we ascertained that each individual patient classified as a responder had a CO increase above LSC [23]. Calculations were also performed using a 15% relative [1,4] or an absolute 300 ml/min/m2 [24] cutoff to define fluid responsiveness.

Variables (expressed as means �� SD or n (%)) were compared using Student’s t-test and Fisher’s exact test (between responders and nonresponders), paired Student’s t-test (for each patient), Cilengitide analysis of variance and the ��2 test (between centers). For each index (��RESPPP, SPV and dDown), we calculated the area under the receiver-operating characteristic curve (AUC), determined positive and negative likelihood ratios (LR+ and LR-) for the best cutoff (Youden method) and for the widely used cutoff of 12% for ��RESPPP [2]. The values of 5 and 10 for LR+ (or 0.2 and 0.1 for LR-) helped to divide the continuous scale of likelihood ratios into three categories: weak, good and strong evidence of discriminative power [25]. AUC values in subgroups of patients were compared [26]. P < 0.05 was considered statistically significant. All statistical tests were two-tailed and performed using MedCalc software (Mariakerke, Belgium) and Statview software (SAS Institute, Cary, NC, USA).ResultsSixty-five patients were included (Table (Table1).1). The mean LSCs of CO measurements were 6.7% and 6.