The Correlational Study Of Pulse Pressure Variation In Various Tidal Volume In Mechanically Ventilated Patients Under General Anaesthesia

Backgroud: Recently, pulse pressure variation (PPV) was recommended as aneffective predictor of fluid responsiveness as well as stroke volume variation (SVV) inpatients with mechanical ventilation. Previous studies demonstrated that the excellentpredictive power was under the tidal volume (VT) higher than8ml/kg, and theaccuracy of PPV under low volume tidal is debating. As known, the setting of VTisnot unchangeable and the protective mechanical ventilation strategy with low tidalvolume and high respiratory rate have been accepted and used widely in clinicalanesthesia. Recently a study reported a significan linear correlation between PPVsunder VT6ml/kg and8ml/kg. So we hypothesized that there were significan linearcorrelations between various PPVs under different tidal volume settings.Objective: To elucidate the relationship between various pulse pressure variationunder different tidal volume.Methods: One hundred adults aged from18-60years scheduled for abdominalsurgeries were selected. The patients were treated with fast induction with midazolam0.05mg/kg, propofol1-2mg/kg, fentanyl3μg/kg and rocuronium0.6mg/kg andventilated with VT of6ml/kg,8ml/kg and10ml/kg in the randomly order at8-14breaths/min respiratory rate after intubation and maintain end-tidal carbon dioxidepartial pressure at30-40mmHg. After tracheal intubation, a artery catheter wasinserted into left radial artery and connected to the bed-side monitor (Philips IntelliVueMP50) and invasive arterial blood pressure, pulse pressure variation (PPV), heart rate(HR), oxygen saturation (SpO2), end-tidal carbon dioxide partial pressure (PetCO2)could been showed real-timely with this equipment. PPV, systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), HR, peakairway pressure (Paw), mean airway pressure (Pmean), respiratory rate (RR) andPetCO2were recorded down. Those parameters were rerecorded down after300mlHydroxyethyl Starch130/0.4and Sodium Chloride Injection infusing in15minutes ifPPV under VT8ml/kg was larger than13%in the initial investigation. Anlysis ofvariance was used for the comparison of normal distribution measurement databetween different tidal volume groups. The Wilcoxon rank sum test was used for thecomparison of non-normal distrbution measurement data between different tidalvolume groups. Pearson correlation analysis was used for the PPVs under differenttidal volume. All differences were considered significant at P <0.05.Results: The PPV was larger than13%under the initial VTsetting of8ml/kg in33patients, who got a rapid infusion of300ml Hydroxyethyl Starch130/0.4and SodiumChloride Injection after the initial observation and then ventilated with another randomVTsettings. Arterial blood pressure, heart rate and HR/RR ratio were similar undervarious ventilation setting (P>0.05). PPV、Paw、Pmean and PetCO2were significantdifferent between these three groups. There was a significant linear correlationbetween PPVs under tidal volume6ml/kg and8ml/kg (r=0.96, P <0.0001), and couldset up the linear regression equation as Y=1.081+1.2462X. There was also a significantlinear correlation between PPV under tidal volume6ml/kg and10ml/kg (r=0.94, P<0.0001) and the linear regression equation could be set up as Y=1.7115+1.5834X. Aswell, it showed a significant linear correlation between PPV under tidal volume8ml/kg and10ml/kg (r=0.98, P <0.0001), the linear regression equationY=0.2428+1.2793X could be set up.Conclusion: The PPVs were different under different settings of VTin patients withthe sanme volume status. The larger of VT, the larger of PPV. Pulse pressure variationunder any one ventilator setting of tidal volume6ml/kg,8ml/kg or10ml/kg couldpredict the pulse pressure variation under the other settings.