传统通气模式与小潮气量或低频通气模式用于正常肺功能患者的比较

Comparison between traditional mechanical ventilation and low tidal volume or respiratory rate ventilation in the patients with normal pulmonary function

目的探讨正常肺功能患者术中单纯降低潮气量(VT)或呼吸频率(RR)是否可以避免过度通气。方法择期行冠状动脉旁路移植术的患者90例,随机均分为三组,全麻诱导后分别采用不同通气模式,传统组:VT8ml/kg,RR12次/分;低频组:VT8ml/kg,调整RR使PETCO2维持在39～41mmHg;小潮气量组:RR12次/分,调整VT使PETCO2维持在39～41mmHg,PETCO2稳定后30min后抽取动脉血行血气分析。结果与传统组比较,低频组和小潮气量组的分钟通气量(MV)、气道峰压(Ppeak)、pH、PaO2均明显降低,但三组PaO2均高于300mmHg。与低频组和小潮气量组比较,传统组发生明显的过度通气和低碳酸血症,PaCO2由基础值(38.7±3.1)mmHg降至(27.3±4.6)mmHg。结论传统通气模式将呼吸参数设定为VT8～10ml/kg,RR10～16次/分,有发生低碳酸血症的可能。根据PETCO2,降低VT到5～7ml/kg或降低RR至7～10次/分避免过度通气可行。

Objective To investigate whether reducing tidal volume or respiratory rate could avoid hyperventilation caused by traditional mechanical ventilation in patients with normal lung function . Methods A single-center randomized controlled trial was undertaken in 90 patients undergoing elective coronary artery bypass graft surgery. Ventilator settings were applied immediately after anesthesia induction. Ninety patients were randomized into 3 groups. Traditional ventilation group received fixed tidal volume （ 8 ml/kg, actual body weight, ABW） and respiratory rate （ 12 breaths/min, bpm）. Low respiratory rate group received fixed tidal volume （ 8 ml/kg） and low tidal volume group received fixed respiratory rate （ 12 bpm）, and whose PETCO2 were maintained at 39-41mmHg by adjusting respiratory rate or tidal volume respectively. Mechanical ventilation parameters and arterial blood gas were assessed at 30min after PETCO2 were stable. Results Compared with those in traditional group, minute volume, Ppeak, PH and PaO2 were lower in next 2 groups, but oxygenation were similar in three groups in terms of the PaO2 were more than 300 mmHg in all patients. In contrast to low respiratory rate group and low tidal volume group, traditional ventilation group has resulted in significant hyperventilation and hypocapnia, accompanied with a decreasing of PaCO2 from （ 38.7±3.1） mmHg to （ 27.3±4.6） mmHg. Conclusion Hypocapnia as a result of hyperventilation could occur in traditional mechanical ventilation （VT： 8-10 ml/kg, RR： 10-16 bpm）. According to the value of PETCO2, it’s feasible to decrease tidal volume to 5-7 ml/kg or reduce respiratory rate to 7-10 bpm to avoid hyperventilation.