Wu Xiao-yan, Huang Ying-zi, Yang Yi, Liu Song-qiao, Liu Huo-gen, Qiu Hai-bo
Department of Critical Care Medicine, Zhongda Hospital and School of Clinical Medicine, Southeast University, Nanjing 210009, China.
Zhonghua Jie He He Hu Xi Za Zhi. 2009 Jul;32(7):508-12.
To observe the effect of neurally adjusted ventilatory assist (NAVA) on patient-ventilator synchrony in patients with acute respiratory distress syndrome (ARDS).
Eighteen patients with ARDS were enrolled in the study. Each patient underwent both an incremental pressure support ventilation (PSV) and NAVA run randomly in 4 steps. The PSV level was gradually increased 5 cm H2O (1 cm H2O = 0.098 kPa) every 5 min from 5 cm H2O until to 20 cm H2O. Incremental NAVA was individually set in steps of 0.2 - 1.0 cm H2O/microV every 5 min to determine the NAVA level predicted to give an airway pressure in each step equivalent to that of PSV. Parameters in patient-ventilator synchrony such as ventilation trigger, ventilation switching and ventilation maintenance were observed at the same time during PSV(PSV1-PSV4) and NAVA(NAVA1-NAVA4).
(1) Ventilation trigger:(1) trigger delay: with progressive increases in PSV, the trigger delays increased significantly (P < 0.05). With increasing NAVA, the trigger delay did not increase significantly (P > 0.05) and each of them was shorter than that of PSV in each corresponding step (P < 0.05). (2) Ineffective trigger: At PSV1, the ineffective triggers accounted for 2. 3% of the neural respiratory rate (NRR), but the ineffective triggers added up to 22% in PSV4 significantly (P < 0.05). All neural efforts were triggered and there were not ineffective triggers at all level in NAVA. (2) Off cycle delay: the off cycle delays in PSV2 - PSV4 increased significantly when compared with PSV1 (P < 0.05). With increasing NAVA, the off cycle delays did not increase significantly (P > 0.05) and each of them was shorter than that of PSV in each corresponding step (P < 0.05). (3) Magnitude of assist [tidal volume (VT)]: The VT [(361 +/- 69) ml] in NAVA1 was equivalent to the VT[(361 +/- 121) ml] in PSV1(P > 0.05). The VT [(417 +/- 71) ml, (427 +/- 80) ml, respectively] in NAVA3-NAVA4 was significantly lower than the VT[(604 +/- 141) ml, (675 +/- 108) ml, respectively] in PSV3-PSV4 (P < 0.05). (4)Respiratory muscle loading: Increasing NAVA and PSV level reduced the magnitude of diaphragm electrical activity (EAdi) and the pressure-time products of esophagus (PTPes) (P < 0.05), but there was no significant difference in each corresponding step of PSV and NAVA(P > 0.05).
Compared with PSV, the ventilation cycle and the magnitude of assist in NAVA matched the patient's breathing pattern. NAVA improved patient-ventilator synchrony in patients with ARDS.
观察神经调节通气辅助（NAVA）对急性呼吸窘迫综合征（ARDS）患者人机同步性的影响。
18例ARDS患者纳入本研究。每位患者均随机分4步依次接受递增压力支持通气（PSV）和NAVA。PSV水平从5 cm H₂O开始，每5分钟逐渐增加5 cm H₂O（1 cm H₂O = 0.098 kPa），直至20 cm H₂O。NAVA以每5分钟0.2 - 1.0 cm H₂O/微伏的步长递增设置，以确定每一步中预计能产生与PSV相同气道压力的NAVA水平。在PSV（PSV1 - PSV4）和NAVA（NAVA1 - NAVA4）过程中，同时观察人机同步性参数，如通气触发、通气切换和通气维持。
（1）通气触发：（1）触发延迟：随着PSV逐渐增加，触发延迟显著增加（P < 0.05）。随着NAVA增加，触发延迟无显著增加（P > 0.05），且在每个相应步骤中均短于PSV（P < 0.05）。（2）无效触发：在PSV1时，无效触发占神经呼吸频率（NRR）的2.3%，但在PSV4时无效触发总计显著增加至22%（P < 0.05）。在NAVA的所有水平上，所有神经驱动均被触发，无无效触发。（2）脱机延迟：与PSV1相比，PSV2 - PSV4的脱机延迟显著增加（P < 0.05）。随着NAVA增加，脱机延迟无显著增加（P > 0.05），且在每个相应步骤中均短于PSV（P < 0.05）。（3）辅助幅度[潮气量（VT）]：NAVA1中的VT[（361 ± 69）ml]与PSV1中的VT[（361 ± 121）ml]相当（P > 0.05）。NAVA3 - NAVA4中的VT[分别为（417 ± 71）ml、（427 ± 80）ml]显著低于PSV3 - PSV4中的VT[分别为（604 ± 141）ml、（675 ± 108）ml]（P < 0.05）。（4）呼吸肌负荷：增加NAVA和PSV水平可降低膈肌电活动（EAdi）幅度和食管压力 - 时间乘积（PTPes）（P < 0.05），但PSV和NAVA的每个相应步骤之间无显著差异（P > 0.05）。
与PSV相比，NAVA的通气周期和辅助幅度与患者呼吸模式相匹配。NAVA改善了ARDS患者的人机同步性。
