Section of Pulmonary Diseases, Critical Care and Environmental Medicine, Tulane University Health Sciences Center, New Orleans, LA 70112, USA.
J Crit Care. 2012 Aug;27(4):418.e1-6. doi: 10.1016/j.jcrc.2011.07.070. Epub 2011 Sep 29.
Rapid shallow breathing index (RSBI) is conveniently measured through the ventilator. If continuous positive airway pressure (CPAP) is used, it may change the RSBI value. We measured the RSBI with a handheld spirometer and through the ventilator, with and without CPAP, to assess differences.
Rapid shallow breathing index was measured in 3 ways: (1) CPAP 0 cm H(2)O and fraction of inspired oxygen (Fio(2)) 0.4, (2) CPAP 5 cm H(2)O and Fio(2) 0.4, and (3) ventilator disconnected and Fio(2) 0.21. Tidal volume and respiratory frequency were recorded from ventilator monitor values in methods 1 and 2, and from a handheld spirometer and observed respiratory frequency, in method 3.
A total of 170 measurements, each using all 3 methods, were obtained from 80 patients admitted to a medical intensive care unit. The mean RSBI values for methods 1, 2, and 3 were 98.1 ± 58.7, 87.6 ± 51.2, and 108.3 ± 65.3, respectively (P < .001). The RSBI decreased by 9.4% when using CPAP 0 cm H(2)O and by 19.1% when using CPAP 5 cm H(2)O.
The RSBI values measured through the ventilator with CPAP 5 cm H(2)O are much lower than the values measured with a handheld spirometer. Even the RSBI values measured with CPAP 0 cm H(2)O are significantly lower. This is attributable to the base flow delivered by some ventilators. The difference must be taken into account during weaning assessment.
快速浅呼吸指数（RSBI）可通过呼吸机方便地测量。如果使用持续气道正压通气（CPAP），可能会改变 RSBI 值。我们使用手持式肺活量计和呼吸机分别在 CPAP 为 0cmH2O 和 CPAP 为 5cmH2O 且吸入氧分数（Fio2）为 0.4 以及呼吸机脱开且 Fio2 为 0.21 时测量 RSBI，以评估差异。
RSBI 通过 3 种方法测量：（1）CPAP 为 0cmH2O，Fio2 为 0.4；（2）CPAP 为 5cmH2O，Fio2 为 0.4；（3）呼吸机脱开，Fio2 为 0.21。方法 1 和 2 中通过呼吸机监测值记录潮气量和呼吸频率，方法 3 中通过手持式肺活量计和观察呼吸频率记录潮气量和呼吸频率。
从重症监护病房的 80 名患者中获得了总共 170 次测量，每种方法各测量 3 次。方法 1、2 和 3 的平均 RSBI 值分别为 98.1 ± 58.7、87.6 ± 51.2 和 108.3 ± 65.3（P<0.001）。使用 CPAP 0cmH2O 时，RSBI 下降 9.4%，使用 CPAP 5cmH2O 时，RSBI 下降 19.1%。
使用 CPAP 5cmH2O 的呼吸机测量的 RSBI 值明显低于使用手持式肺活量计测量的 RSBI 值。即使使用 CPAP 0cmH2O 测量的 RSBI 值也显著降低。这归因于一些呼吸机提供的基础气流。在脱机评估时必须考虑到这一差异。
