Feasibility of using corrected body weight to set tide volume for mechanical ventilation during general anesthesia in obese patients / 中国医师进修杂志

ABSTRACT

Objective To evaluate the feasibility of using corrected body weight to set the tide volume for mechanical ventilation during general anesthesia in obese patients.Methods Ninety-six ASA physical status Ⅰ or Ⅱ obese patients,with a body mass index of 28-44 kg/m2,scheduled for elective extremity surgery under general anesthesia,were divided into 3 groups (32 cases of each group) by random digits table method:tide volume based on actual body weight group (group A),tide volume based on ideal body weight group(group B),and tide volume based on corrected body weight group(group C).The pulmonary function of all patients was normal.The patients were endotracheally intubated and mechanically ventilated after induction of anesthesia.According to the corresponding body weight,the initial tide volume was set based on 8 ml/kg in each group(respiratory rate15 bpm).At 10 min after start of mechanical ventilation,peak airway pressure (Ppeak),airway plateau pressure (Pplat),airwayresistance (Raw) were recorded.Arterial blood samples were collected at 30 min of mechanical ventilation for blood gas analysis and arterial blood oxygen partial pressure (PaO2),arterial blood carbon dioxide partial pressure (PaCO2) and the patients requiring readjustment of tide volume were also recorded.Results The level of Ppeak,Pplat,Raw in group B and group C were significantly lower than those in group A[(15.3 ± 1.8),(18.5 ± 2.6) cmH2O (1 cmH2O =0.098 kPa) vs.(23.2 ±3.3) cmH2O; (11.5 ± 1.6),(14.3 ± 1.4) cmH2O vs.(17.6 ±2.7) cmH2O; (10.8 ± 1.7),(12.5 ± 2.6) cmH2O/ (L·s) vs.(16.8 ± 3.0) cmH2O/ (L·s)],and the level of PaCO2 in group B and group C was significantly higher than that in group A [(48.8 ± 3.1),(40.2 ± 2.3) mmHg (1 mmHg =0.133 kPa) vs.(28.6 ± 3.8) mmHg],there was significant difference(P ＜ 0.01).The level of PaO2 and oxygenation index in three groups had no significant difference (P ＞ 0.05).There were no patients requiring readjustment of tide volume in group C,however,93.8％ (30/32) patients required readjustment of tide volume in group A and 81.2 ％ (26/32) in group B,there was significant difference (P ＜ 0.01).Conclusion Corrected body weight based on 8 ml/kg can be used to set the tide volume for mechanical ventilation during general anesthesia in obese patients with normal pulmonary function.