应用COPD模型观察比例辅助通气时不同参数设置对人机同步及呼吸做功的影响

Effects on synchronization and work of breathing with different assistance levels during proportional assist ventilation： a bench study

目的 观察比例辅助通气 （PAV）时不同通气参数设置对慢性阻塞性肺疾病 （COPD）力学模型的呼吸做功和人机同步性影响。方法 使用ASL5000肺模拟器模拟COPD患者,设置系统顺应性为60ml/cm H2O [即弹性阻力 （Ers）为16 7cmH2O/L]、气道阻力为20cmH2O·L ·s^-1。吸气时间为1 6s,呼吸频率为15次/min。RespironicsV60呼吸机以PAV模式运行,流量辅助 （FA）为20cmH -1 -12O·L ·s^-1,容量辅助 （VA）分别为10cmH2O/L、20cmH2O/L和30cmH2O/L,辅助比例分别为20%、40%、60%和80%。呼气末正压为5cmH2O,后备通气频率为10次/min。收集在系统泄漏量为25-28L/min时的通气参数变化。结果 无论 VA预设值的变化,低水平 （≤40%）FA＋VA辅助均无法提供有效通气;当VA预设值为30cmH2O/L时,较高水平 （〉60%）FA＋VA辅助极易出现脱逸。随着FA辅助比例的增高,吸气峰流速和气道峰压逐渐增高,吸气时间和吸气触发做功却显著降低,FA 辅助比例为80%时出现严重的过早切换 [（-439.70±15.95）ms比（-284.10±11 67）ms,P 〈0.05]。随着VA预设值和辅助比例的增高,潮气量也逐渐增大;当VA辅助水平为约90%Ers并联合50%FA辅助时,过早切换现象明显减轻,仅为 （-241.10±26 96）ms。结论 PAV通过采用正反馈调节机制,成比例地提供同步通气辅助。通过最优化设置通气参数可有助于改善人机同步性,减轻呼吸做功。

Objective To evaluate the effects on patient-ventilator synchrony and work of breathing in obstructive model during proportional assist ventilation （PAV） with different assistance levels. Methods The respironics V60 ventilator was connected to a ASL5000 lung simulator, which simulate lung mechanics in patients with chronic obstructive pulmonary disease （COPD） [compliance/elastance= 60 ml/emH20/16.7 cmH20/L, airway resistance= 20 cmH20·L ·s^-1, inspiratory time= 1.6 s, breathing rate= 15 bpm]. PAV was applied with different levels of assistance [flow assist （FA）= 20 cmH20·L ·s^-1 , volume assist （VA） = 10/20/30 cmH2 O/L） and proportion= 20 %-80 %]. PEEP was 5 cmH2O, back-up rate was 10 bpm. Measurements were conducted at system leaks with 25-28 L/rain. The performance characteristics and patient-ventilator asynchrony were assessed, including flow, airway pressure, time and workload. Results Hypoventilation was existed during PAV with lower assist level （-40%） of FA and VA. Run-away might be prone to occured if the FA VA proportion was exceed 60 -, which VA preset value was 30 emil20/L. As the level of FA rised, peak inspiratory flow and peakinspiratory pressure were increased gradually, while inspiratory time and breathing effort were reduced, and severe premature was observed at 80M FA support [-（-439.70±15.95） ms vs （--284.10±11.67） ms, P〈0. 053. Better cycling synchrony （-241.10± 26.96） ms was found during PAV with moderate level of FA （50% Raw） and higher level of VA （about 90M Ers）. Conclusions As a positive feedback system, PAV with appropriate proportion level seems more efficacious in decreasing the work of breathing during the inspiratory phase, resulting in fewer patient-ventilator asynchronies. An optimal setting with FA and VA may be beneficial for breathing support.