Kheir Fayez, Myers Leann, Desai Neeraj R, Simeone Francesco
Section of Pulmonary Diseases, Critical Care and Environmental Medicine, Tulane University Health Sciences Center, New Orleans, LA, USA
Department of Biostatistics, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA.
J Intensive Care Med. 2015 Feb;30(2):103-6. doi: 10.1177/0885066613504538. Epub 2013 Sep 24.
The rapid shallow breathing index (RSBI) has the best predictive value to assess readiness for weaning from mechanical ventilation. At many institutions, this index is conveniently measured without disconnecting the patient from the ventilator, but this method may be inaccurate. Because modern ventilators have a base flow in the flow trigger mode that may provide a substantial help to the patient, we hypothesized that the RSBI is significantly decreased when measured through the ventilator with flow trigger even without continuous positive airway pressure (CPAP) and pressure support (PS).
The RSBI was calculated using the values of minute ventilation and respiratory rate obtained either through the digital display of the ventilator or from a digital ventilometer. The RSBI was measured using 3 different methods: method 1, CPAP and PS both 0 cm H2O with flow trigger; method 2, CPAP and PS both 0 cm H2O without flow trigger; and method 3, using digital ventilometer.
A total of 165 measurements per method were obtained in 80 adult patients in the medical intensive care unit (MICU). The RSBI (breaths/min/L) values were 70.2 ± 26.5 with method 1, 85.4 ± 30.3 with method 2, and 80.1 ± 30.3 with method 3. The RSBI was significantly decreased using mechanical ventilation with flow trigger as compared with mechanical ventilation without flow trigger (P < .0001) or digital ventilometer (P < .0001). When method 1 was compared with methods 2 and 3, the RSBI decreased by 17% and 12%, respectively.
The RSBI measurement is significantly decreased by the base flow delivered through modern ventilators in the flow trigger mode. If RSBI is measured through the ventilator in the flow trigger mode, the difference should be considered when using RSBI to assess readiness for weaning from mechanical ventilation.
快速浅呼吸指数（RSBI）对评估机械通气撤机准备情况具有最佳预测价值。在许多机构中，该指数可在不将患者与呼吸机断开连接的情况下方便地测量，但这种方法可能不准确。由于现代呼吸机在流量触发模式下有基础流量，这可能会为患者提供很大帮助，我们推测即使在没有持续气道正压通气（CPAP）和压力支持（PS）的情况下，通过带有流量触发的呼吸机测量时，RSBI也会显著降低。
RSBI通过呼吸机数字显示屏或数字通气量计获得的分钟通气量和呼吸频率值来计算。RSBI采用3种不同方法测量：方法1，CPAP和PS均为0 cm H₂O且带有流量触发；方法2，CPAP和PS均为0 cm H₂O且无流量触发；方法3，使用数字通气量计。
在医疗重症监护病房（MICU）的80例成年患者中，每种方法共获得165次测量值。方法1的RSBI（次/分钟/升）值为70.2±26.5，方法2为85.4±30.3，方法3为80.1±30.3。与无流量触发的机械通气（P<.0001）或数字通气量计（P<.0001）相比，使用带有流量触发的机械通气时RSBI显著降低。当方法1与方法2和3比较时，RSBI分别降低了17%和12%。
现代呼吸机在流量触发模式下输送的基础流量会使RSBI测量值显著降低。如果通过流量触发模式的呼吸机测量RSBI，在使用RSBI评估机械通气撤机准备情况时应考虑这种差异。
