Sasaki Makoto, Yamaguchi Yoshikazu, Miyashita Tetsuya, Matsuda Yuko, Ohtsuka Masahide, Yamaguchi Osamu, Goto Takahisa
Department of Anesthesiology and Critical Care Medicine, Yokohama City University, 3-9 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa, 236-004, Japan.
Department of Critical Care Medicine, Yokohama City University Medical Center, Yokohama, Japan.
Intensive Care Med Exp. 2019 Feb 8;7(1):10. doi: 10.1186/s40635-019-0223-8.
Endotracheal tubes used for neonates are not as resistant to breathing as originally anticipated; therefore, spontaneous breathing trials (SBTs) with continuous positive airway pressure (CPAP), without pressure support (PS), are recommended. However, PS extubation criteria have predetermined pressure values for each endotracheal tube diameter (PS 10 cmHO with 3.0- and 3.5-mm tubes or PS 8 cmHO with 4.0-mm tubes). This study aimed to assess the validity of these SBT criteria for neonates, using an artificial lung simulator, ASL 5000™ lung simulator, and a SERVO-i Universal™ ventilator (minute volume, 240-360 mL/kg/min; tidal volume, 30 mL; respiratory rate, 24-36/min; lung compliance, 0.5 mL/cmHO/kg; resistance, 40 cmHO/L/s) in an intensive care unit. We simulated a spontaneous breathing test in a 3-kg neonate after cardiac surgery with 3.0-3.5-mm endotracheal tubes. We measured the work of breathing (WOB), trigger work, and parameters of pressure support ventilation (PSV), T-piece breathing, or ASL 5000™ alone.
WOB displayed respiratory rate dependency under intubation. PS compensating tube resistance fluctuated with respiratory rate. At a respiratory rate of 24/min, the endotracheal tube did not greatly influence WOB under PSV and the regression line of WOB converged with the WOB of ASL 5000™ alone under PS 1 cmHO; however, at 36/min, endotracheal tube was resistant to breathing under PSV because trigger work increased exponentially with PS ≤ 9 cmHO. The regression line of WOB under PSV converged with the WOB of T-piece breathing under PS 1 cmHO. Furthermore, PS compensating endotracheal tube resistance was 6 cmHO. The WOB of ASL 5000™ alone approached that of respiratory distress syndrome (RDS); however, the pressure of patient effort was normal physiological range at PS 10 cmHO. PS equalizing WOB under PSV with that after extubation depended on the respiratory rate and upper airway resistance. If WOB after extubation equaled that of T-piece breathing, the PS was 0 cmHO regardless of the respiratory rates. If WOB after extubation approximated to that of ASL 5000™ alone, the PS depended on the respiratory rate.
SBT strategies should be selected per neonatal respiratory rates and upper airway resistance.
用于新生儿的气管内导管对呼吸的阻力不如最初预期的那样；因此，建议在没有压力支持（PS）的情况下进行持续气道正压通气（CPAP）的自主呼吸试验（SBT）。然而，PS拔管标准为每个气管内导管直径预先设定了压力值（3.0和3.5毫米导管的PS为10厘米水柱，4.0毫米导管的PS为8厘米水柱）。本研究旨在使用人工肺模拟器ASL 5000™肺模拟器和SERVO-i Universal™呼吸机（分钟通气量，240 - 360毫升/千克/分钟；潮气量，30毫升；呼吸频率，24 - 36次/分钟；肺顺应性，0.5毫升/厘米水柱/千克；阻力，40厘米水柱/升/秒）在重症监护病房评估这些SBT标准对新生儿的有效性。我们使用3.0 - 3.5毫米气管内导管模拟了一名3千克新生儿心脏手术后的自主呼吸测试。我们测量了呼吸功（WOB）、触发功以及压力支持通气（PSV）、T形管呼吸或单独使用ASL 5000™时的参数。
插管状态下WOB显示出呼吸频率依赖性。补偿气管导管阻力的PS随呼吸频率波动。在呼吸频率为24次/分钟时，气管内导管在PSV下对WOB影响不大，且在PS为1厘米水柱时WOB的回归线与单独使用ASL 5000™时的WOB收敛；然而，在36次/分钟时，气管内导管在PSV下对呼吸有阻力，因为当PS≤9厘米水柱时触发功呈指数增加。PSV下WOB的回归线在PS为1厘米水柱时与T形管呼吸的WOB收敛。此外，补偿气管导管阻力的PS为6厘米水柱单独使用ASL 5000™时的WOB接近呼吸窘迫综合征（RDS）的情况；然而，在PS为10厘米水柱时患者用力的压力处于正常生理范围。使PSV下的WOB与拔管后的WOB相等取决于呼吸频率和上气道阻力。如果拔管后的WOB等于T形管呼吸的WOB，则无论呼吸频率如何，PS均为0厘米水柱。如果拔管后的WOB接近单独使用ASL 5000™时的WOB，则PS取决于呼吸频率。
应根据新生儿呼吸频率和上气道阻力选择SBT策略。
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