Objective To evaluate the accuracy of an expiratory resistance device assisting pulse pressure variation (PPV) in predicting volume responsiveness in the spontaneously breathing patients.Methods Forty spontaneously breathing patients of both sexes,aged 22-61 yr,weighing 51-73 kg,of American Society of Anesthesiologists physical status Ⅰ or Ⅱ,undergoing elective operation,were enrolled.Before induction of anesthesia,mean arterial pressure (MAP),heart rate (HR),central venous pressure (CVP),cardiac index (CI) and pulse pressure variation (PPVB) were recorded after haemodynamics were stable.Then the expiratory resistance device was used,and MAP,HR,CVP,CI,and PPVA were recorded.The device was then removed.Volume expansion was carried out.6％ hydroxyethyl starch 130/0.4 6 ml/kg was infused over 10 min.MAP,HR,CVP,CI and PPVB were recorded within 3 min after volume expansion.The device was used again,and 1 min later MAP,HR,CVP,CI and PPVA were recorded.The device was then removed.The patients were divided into 2 groups according the percentage of increase in CI after volume expansion (△ CI):△ CI≥ 15％ considered to be a positive response group (group P),and ACI＜15％ considered to be a negative response group (group N).A receiver-operating characteristic (ROC) curve for PPV was plotted.According to the ROC curve,the diagnostic threshold,sensitivity,specificity,area under the curve,and 95％ confidence interval of the expiratory resistance device assisting PPV in predicting volume responsiveness were determined.Results The area under the curve (95％ confidence interval) of PPVA was 0.880 (0.70-0.98),the diagnostic threshold was 13.5％,and the sensitivity and specificity in determining volume responsiveness were 87％ and 88％,respectively.Compared with the value before administration of the loading dose,the CVP and CI were significantly increased,and PPVB and PPVA were decreased after volume expansion in group P,and the CVP and CI were significantly increased after volume expansion in group N (P＜0.05).Compared with group P,the PPVA was significantly decreased before volume expansion,and the CI was increased after volume expansion in group N (P＜0.05).Conclusion The expiratory resistance device can assist PPV in predicting volume responsiveness in the spontaneously breathing patients.