开胸手术前后氧耗量和呼吸氧价的变化

The oxygen consumption and oxygen cost of breathing before and after thoracotomy

目的 研究麻醉手术前后病人的氧耗量和呼吸氧价（OCB）的变化以及常用各种辅助通气方式对OCB的影响。方法 选择20例胸科手术病人,术前没有慢性肺部疾病病人10例为非肺病组,有慢性肺部病史的病人10例为肺病组,于手术前和手术后12h用代谢监测仪分别对病人进行代谢测定,比较病人术前术后VO2变化和手术后两组病人在自主呼吸、CPAP、SIMV和PSV等通气方式下的OCB。结果 非肺病组和肺病组病人开胸手术前后VO2有明显的改变,术后EE明显高于术前,特别是肺病组;非肺病组病人手术后OCB为9.2％±3.5％,而肺病组病人手术后OCB为15.4％±7.7％。CPAP可使非肺病组和肺病组病人OCB分别下降 1.3％±1.2％（P<0.05）和3.4％±2.9％（P<0.05）,SIMV不能降低非肺病组和肺病组病人术后OCB（P>0.05）,PSV不能使非肺病组病人OCB降低（P>0.05）,但可使肺病组病人的OCB下降6.3％±4.6％（P<0.05）。结论 开胸手术术后病人VO2明显高于术前,肺病病人更明显;术后非肺病和肺病病人自主呼吸下OCB均增高,而PSV和CPAP可明显降低OB,SIMV不能降低手术后病人OCB。

Objective To study the changes in oxygen consumption ( VO2 ) and oxygen cost of breathing(OCB) in postoperative patients and the effects of various kinds of assisted ventilatory support on OCB.Methods Twenty patients (13 male, 7 female), aged 43-70 years, undergoing thoracic surgery were divided into two groups: (A) pulmonary disease(PD) group in which patients had chronic pulmonary disease and abnormal pulmonary function( n = 10); non-pulmonary disease (NPD) group in which patients had no chronic pulmonary disease and their pulmonary function was normal ( n = 10). Operation were performed under combined intravenous-inhalation anesthesia or general-epidural anesthesia. Metabolism of the patients was measured before anesthesia. After operation the patients were mechanically ventilated in ICU and PaCO2 was maintained between 4.6-6.0 kPa. Metabolism was measured 12h after operation when anesthesia had worn off, the patients were fully awake and breathing spontaneously. Their hemodynamics was stable. Body temperature was maintained at 37℃±0.5℃ . VO2 was measured using indirect colorimetry (Datex Deltatrac MBM-200). VO2, VCO2, energy expenditure(EE) and respiratory quotient (RQ) were recorded every minute for 30 min. OCB was calculated by deducting VO2 measured during controlled ventilation from VO2 measured during spontaneous breathing( OCB = VO2 spontaneous breathing - VO2 controlled ventilation) and expressed by OCB/VO2 spontaneous breathing ( % ) . During mechanical ventilation FiO2 was set <50%, PEEP at 5 cm H2O and pressure support was adjusted to maintained tidal volume(VT) at 8 ml/kg. Results VO2 increased after operation in both groups as compared with the baseline(measured before anesthesia)(P<0.05). The increase in VO2 was larger in PD group than that in NPD group. Postoperative OCB was 9.2% ** 3.5% in NPD group and 15.4% ±7.7% in PD group. CPAP could decrease OCB by 1.3 %±1.2 % in NPD group and 3.4 %±2.9 % in PD group. SIMV did not decrease OCB in either group. PSV did not decrease OCB in NPD group but decreased OCB by6.3% ±4.6% in PD group.Conclusions VO2 increases significantly after thoracotomy especially in patients with chronic pulmonary disease. OCB increases after thoracotomy in both patients with and without pulmonary disease. Both PSV and CPAP can decrease OCB in patients with chronic pulmonary disease after operation.