【摘要】 目的探讨应用强迫振荡电抗(Xrs)评估COPD患者的呼气流速受限(EFL)的程度和持续气道正压(CPAP)水平的合理性。方法纳入8例稳定期COPD并Ⅱ型呼吸衰竭患者,取坐位经鼻罩CPAP通气,压力水平分别设为4、8和12 cm H2O。通过振荡发生器向呼吸管道内施加频率为5 Hz、振幅为2 cm H2O的强迫振荡,测量鼻腔压力和流量,采用频谱分析技术计算各呼吸周期的呼气与吸气相电抗之差(ΔXrs)并求各压力水平下的均值;经鼻放置食管测压囊管同步检测食管压力,计算跨气道压,分析各呼吸周期的跨气道压与流量的关系,将呼吸周期划分为EFL呼吸周期和非EFL呼吸周期。试验前8例患者各采集一套自然呼吸时(CPAP=0 cm H2O)的食管压力和流量信号,分析各呼吸周期的EFL情况作为基线水平。比较各CPAP水平下ΔXrs值与EFL呼吸周期数的相互关系,计算检测EFL呼吸周期敏感性和特异性均最高的ΔXrs阈值,计算可消除绝大部分呼吸周期气流受限的CPAP水平。结果①CPAP水平增高,ΔXrs值降低,与CPAP为4、8和12 cm H2O对应的ΔXrs的均值分别为2.67、1.62和1.31 cm H2O.s-1.L-1(CPAP为0 cm H2O时未计算ΔXrs值),其中CPAP从4 cm H2O提高至8 cm H2O时,ΔXrs下降的幅度有统计学意义(Z=-2.68,P=0.01)。②CPAP通气使显示为EFL的呼吸周期数显著减少,CPAP从0 cm H2O提高至4、8和12 cm H2O时,EFL呼吸周期数占全部呼吸周期数的百分比从29.8%分别减少至9.9%、8.1%和4.4%(2=15.6,P=0.01)。③EFL呼吸周期的ΔXrs值显著大于非EFL呼吸周期,分别为(5.95±2.53)和(-0.05±0.62)cm H2O.s-1.L-1(t=11.5,P<0.01)。ΔXrs为1.83 cm H2O.s-1.L-1是区分呼吸周期有或无EFL的阈值,敏感性和特异性分别为94%和97%。结论5 Hz强迫振荡测定的ΔXrs反映了气流受限的程度,在COPD患者无创通气时,逐步调节CPAP水平使ΔXrs值等于或低于1.83 cmH2O.s-1.L-1能消除绝大部分呼吸周期的EFL。更多还原

【Abstract】 Objective To assess the effect of continuous positive airway pressure(CPAP) on expiratory flow limitation in severe chronic obstructive pulmonary disease(COPD) patients during noninvasive ventilation by oscillatory reactance(Xrs).Methods Eight patients with stable COPD and chronic hypercapnic respiratory failure(type II) received noninvasive ventilation with a traditional CPAP ventilator through a nasal mask were enrolled.The CPAP were successively set as 4,8 and 12 cm H2O respectively.The forecd oscillation(5 Hz,2 cm H2O) was imposed into the mask and the flow and nasal pressure were measured at the airway opening.The difference between inspiratory and expiratory Xrs(ΔXrs) were calculated for each breathing cycle and average ΔXrs was calculated at different pressure levels according to the established algorithm.Meanwhile,the oesophageal pressure was also measured by a balloontipped catheter and transpulmonary pressure was calculated.The breathing cycles above were analyzed subsequently and classified as expiratory flow-limited(EFL) and non-EFL breath.In addition,flow and nasal pressure when breathing naturally(CPAP=0 cm H2O) was also collected for each patient and the EFL breath cycles was identified as baseline.Then,the percentage of EFL breathing cycles and ΔXrs were calculated for each CPAP level and their relationship was analyzed.The threshold value of ΔXrs with maximum sensitivity and specificity to detect EFL and the optimal CPAP to suppress the development of EFL were computed.Results ①CPAP increased from 4 to 8 and 12 cm H2O resulted in fall of mean values of ΔXrs from 2.67 to 1.62 and 1.31 cm H2O·s-1·L-1,respectively(ΔXrs at CPAP 0 cm H2O was not detected),and the decrease of ΔXrs when CPAP up to 8 cm H2O from 4 cm H2O was significant(Z=-2.68,P=0.01).②CPAP significantly suppressed the development of EFL,when CPAP increased from 0 cm H2O to 4,8 and 12 cm H2O resulted in decrease in the percentage of breathing cycle from 29.8% to 9.9%,8.1% and 4.4%,respectively(2=15.6,P=0.01).③ΔXrs was related to the degree of EFL and the mean value of ΔXrs in EFL breathing cycles was significantly higher than that in non-EFL’s.When ΔXrs decreased to 1.83 cm H2O·s-1·L-1,the majority of breath showed non-EFL,with a sensitivity of 94% and specificity of 97% for detecting EFL,respectively.Conclusions ΔXrs is an indicator of the occurrence of EFL.Appropriate CPAP to render the value of ΔXrs equal to or slightly less than 1.83 cm H2O·s-1·L-1 may effectively suppress the development of EFL in severe COPD patients during noninvasive ventilation.更多还原