不同频率辅助通气对机械通气患者血流动力学的影响

The influence of different respiratory frequencies on hemodynamics in patients on artificial ventilation

目的探讨不同频率辅助通气对机械通气患者血流动力学的影响。方法选择重症加强治疗病房（ICU）尝试撤机阶段的12例危重病患者,机械通气模式均为双水平气道正压（BiPAP）通气,仅调整通气频率,保持吸气压力及呼气末正压（PEEP）不变,按随机原则将呼吸频率先后设置为5、10、15和20次/min,记录各设置调整20min后的呼吸力学、氧合及血流动力学指标变化。结果1随着设定呼吸频率的增加,平均气道压（Pmean）、控制通气分钟通气量（VEcontrol）逐渐增加,而自主呼吸分钟通气量（VEspont）则逐渐减少（P均〈0.01）,患者各呼吸频率间总的呼吸频率、分钟通气量（VE）均无明显变化,动脉血二氧化碳分压（PaCO2）、氧合指数（PaO2/FiO2）差异也无显著性（P均〉0.05）;2随着设定呼吸频率的降低,每搏量指数（SI）、心排血指数（CI）、全心舒张末期容积指数（GEDVI）、胸腔内血容积指数（ITBVI）显著增加（P均〈0.01）,但患者各呼吸频率间心率（HR）、中心静脉压（CVP）、平均动脉压（MAP）、体循环阻力指数（SVRI）及血管外肺水指数（EVLWI）相对恒定（P均〉0.05）;3CI与GEDVI呈显著正相关（r=0.569,P〈0.01）。结论对于机械通气的患者,随着自主呼吸与控制通气比例的增加,心脏前负荷增加,心排血量增加。

Objective To discuss the influence of different mechanical respiratory frequencies on hemodynamics in patients on mechanical ventilator. Methods Twelve critical patients during weaning from mechanical ventilation with bi -level positive airway pressure （BiPAP） were studied. The ventilatory support was modified by changing the mechanical respiratory frequency only, with inspiratory airway pressure and positive end - expiratory pressure （PEEP） kept constant. Mechanical respiratory frequency was set as follows： 5, 10, 15 and 20 breaths per minute in randomized order. Respiratory mechanics, oxygenation and hemodynamics were determined and recorded 20 minutes after the change in ventilatory parameters. Results （1）With the increase in mechanical respiratory rate, the mean pressure （Pmean） increased, minute ventilatory volume in control ventilation （VE control） were also significantly increased, but minute ventilatory volume in spontaneous breaths （VEspont） were decreased （all P〈0.01）. There were no change in the total respiratory frequencies, minute ventilatory volume （VE）, partial pressure of carbon dioxide in artery （PaCO2） and oxygenation index （PaO2/FiO2, all P〉0. 05）. （2）With the decrease in mechanical respiratory frequencies, stroke volume index （SI）, cardiac output index （CI）, global end - diastolic volume index （GEDVI） and intrathoracic blood volume index （ITBVI）were also increased （all P〈0. 01）, but heart rate （HR）, central venous pressure （CVP）, mean artery pressure （MAP）, systemic vascular resistance index （SVRI） and extravascular lung water index （EVLWI） were relatively stable （all P〉0. 05）.（3）There was significant positive correlation between CI and GEDVI （r=0. 569, P〈0. 01）. Conclusion With an increase in the ratio of spontaneous breaths to control ventilation in patients on mechanical ventilator, cardiac preload is increased, so cardiac output is also increased.