无创正压通气回路中测压管内冷凝液对志愿者人机同步的影响

The influence of condensate in the piezometric tube on patient ventilator interaction during noninvasive positive pressure ventilation

目的 探讨无创机械通气回路测压管内冷凝液对人机同步的影响.方法 在11名健康人无创正压通气期间,向通气回路测压管中段内逐渐注入不同容量的生理盐水直至实验者不能触发呼吸机送气或注水总量达到1.5 ml,观察面罩内压力(Pmask)、测压管近面罩端压力(Ppro)、测压管近呼吸机端压力(Pdis)和呼吸流量(Flow)的动态变化.结果 (1)经Pmask测得的触发时间、触发压力和触发做功分别从注水前0.09(0.07～0.11)s、0.26(0.15 ～0.33) cmH2O和0.02(0.01～0.03)cmH2O·s增加到最大时的0.31 (0.22 ～0.39)s、2.29(1.76 ～ 3.09) cmH2O和0.55(0.41～0.68)cmH2O·s;无效触发从0次/min最多增多到9次/min;误触发从0次/min最多增多到33次/min.(2)注水后经Pmask和Ppro测得的平台压高于预设值,分别从注水前(9.74 ±0.34)和(9.80±0.31)cmH2O增高到最大时(15.79±3.10)和(15.44±3.47) cmH2O,经Pdis测得的平台压注水前为(9.85±0.29)cmH2O,注水后最高为(12.58-±2.64) cmH2O.(3)注水后经Pmask和Ppro测得的基线压分别从(3.67±0.36)和(3.71 ±0.32) cmH2O增高到最大时(8.40±3.22)和(8.13±3.55)cmH2O,经Pdis测得的基线压从(3.77 ±0.32) cmH2O增高至(5.36±1.25)cmH2O.(4)注水后送气压力波动明显,经Pmask测得的平台压波动幅度从注水前0.60(0.48～0.71)cmH2O增大到最大时7.94(7.11～ 8.63)cmH2O,单个呼吸周期平台压波动频率从0次增加到最多时7次.(5)注水后,吸气触发呼吸机送气后,Pdis到达平台压的时间较Pmask、Ppro延迟,延迟最长为0.11(0.08～0.12)s.结论 无创通气期间,测压管内冷凝水会影响人机同步,应避免测压管内出现冷凝水.

Objective To study the effects of condensate in the piezometric tube on patient ventilator interaction during noninvasive positive pressure ventilation.Methods Eleven healthy adults volunteered to receive noninvasive positive pressure ventilation.Different capacity of physiological saline was injected gradually into the piezometric tube until the volunteers could not trigger the ventilator or the total volume of the water reached 1.5 ml.The dynamic changes of the pressure of mask (Pmask),piezometric tube near mask (Ppro),piezometric tube near breathing machine (Pdis),and the flow were observed.Results With increasing volume of saline injected,the trigger time Thri (Pmask) increased from 0.09 (0.07-0.11) to 0.31 (0.22-0.39) s,the trigger pressure TPtri (Pmask) increased from 0.26 (0.15-0.33) to 2.29(1.76-3.09) cmH2O,and the pressure-time product PTP (Pmask) increased from 0.02 (0.01-0.03) to 0.55 (0.41-0.68) cmH2O · s.Ineffective triggering rate increased from 0 up to 9 times/min,and spurious triggering rate increased from 0 up to 33 times/min.The plateau pressure of Pmask and Ppro exceeded the preset parameters,increased significantly as compared with 0 ml,from (9.74 ± 0.34)to (15.79±3.10) cmH2O and from(9.80±0.31) to(15.44 ±3.47) cmH2O.The change of plateau pressure of Pdis was not significant [from (9.85 ± 0.29) to (12.58 ± 2.64) cmH2O].The baseline pressure of Pmask,Ppro and Pdis changed from (3.67 ±0.36) to (8.40 ±3.22) cmH2O,from (3.71 ± 0.32) to (8.13 ±3.55) cmH2O and from(3.77 ±0.32) to (5.36 ± 1.25) cmH2O,respectively.The pressure fluctuation of platform of Pmask increased significantly compare with 0 ml,from 0.60 (0.48-0.71) to 7.94(7.11-8.63)cmH2O.The frequency of fluctuation of platform increased as many as 7 times during a single respiratory period.The time when the pressure of the Pdis began to change was delayed to Pmask and Ppro,0.11 (0.08-0.12) s compared with 0 ml.Conclusion Condensate in the piezometric tube during noninvasive positive pressure ventilation could influence patient-ventilator synchrony.To improve patient ventilator interaction in noninvasive positive pressure ventilation,condensate in the piezometric tube should be avoided.