2006 OPEN FORUM Abstracts
COMPARSIONS OF RAPID SHALLOW BREATHING INDEX, ADVERSE REACTIONS, AND PREDICTIVE ACCURACY IN THE SAME PATIENT GROUP WITH AND WITHOUT VENTILATORY SUPPORT
Mauo-Ying Bien PhD RPT RRT, Yu Ru Kou PhD, Huei-Guan Shie MPH RRT, You-Lan Yang
MS, Chung-Hung Shih, MD PhD, Jia-Horng Wang MD, Kuo-Chen Cheng MD. School of
Respiratory Therapy, Taipei Medical University, Taipei, Taiwan, R. O. C.
Background: The rapid shallow breathing index (RSBI) measured during
spontaneous breathing has been widely used as a predictor for weaning outcome. RSBI can be measured when patients are disconnected from the ventilator (RA-no
ventilator) or are still connecting to the
ventilator. So far, there is no study comparing the RSBI values, the incidence of
adverse reaction, and the predictive accuracy measured by these two methods. This study was conducted to compare these
clinical endpoints under the conditions
of RA-no ventilator and 4 different settings of ventilatory support before weaning
trials in the same patient group.
Methods: 98 mechanically
ventilated medical patients ready for weaning were included. They were divided
into success (n=71) and failure (n=27) groups based upon their
weaning outcome. Before weaning, spontaneous minute ventilation and respiratory
frequency were measured for 1 minute, and average tidal volume and RSBI were
calculated under 5 conditions: RA-no ventilator; FiO2: 21%,
CPAP: 0 or 5 cmH2O; and FiO2: 40%, CPAP: 0 or 5 cmH2O. The
sequences of the conditions were randomized and at least 5 minutes were elapsed
between any 2 conditions. After the patients successfully completely the
weaning trials, they were extubated. Successful weaning was defined as patients
free from the ventilator for over 48 hours. Friedman repeated measures analysis
of variance on ranks and Dunn's method were used to compare the RSBI values.
The predictive performances of the RSBI measured in 5 conditions, their pair
wise comparisons, and the most appropriate cut-off values were assessed by
analysis of the receiver operating characteristic (ROC) curve. Data are
presented as mean ± SD. P < 0.05
was considered significant.
Results: The RSBI values measured under 4 conditions
of ventilator settings were higher than that of RA-no ventilator. The changes in pulse rate and blood pressure
post-measurement were within the clinically acceptable ranges, but the
incidence of occurring respiratory rate ³ 35/min or oxygen
saturation £ 89% (adverse reaction) was highest under
the conditions of 21%-0 cmH2O and 21%-5 cmH2O and lowest under
the condition of 40%-5 cmH2O. The areas under ROC curve measured
under these 5 conditions were within the range of 0.51-0.62 indicating their
predicative accuracy; no significant difference was detected between any 2 conditions.
The RSBI values of 91 and 105 breaths/min/L under the conditions of RA-no ventilator and 40%-5 cmH2O,
respectively, were the optimal cut-off values in this patient group.
| RR, b/min | VE, LPM | VT, L | RSBI, b/min/L | Adverse Reaction | |
| RA-no ventilator | 23.29 ± 6.24 | 7.93 ± 2.61 | 0.352 ± 0.112 | 74.54 ± 33.53 | 16 |
| 21%-0 cmH2O | 24.88 ± 6.26 | 7.26 ± 2.41 | 0.307 ± 0.126a | 97.51 ± 50.25a | 20 |
| 21%-5 cmH2O | 24.06 ± 5.80 | 7.15 ± 2.24a | 0.310 ± 0.112a | 90.28 ± 43.64a | 20 |
| 40%-0 cmH2O | 24.12 ± 5.86 | 7.14 ± 2.25a | 0.309 ± 0.110a | 92.01 ± 51.19a | 4 |
| 40%-5 cmH2O | 23.27 ± 5.88b,c | 6.85 ± 2.36a,b,c | 0.308 ± 0.120a | 91.53 ± 53.74a | 2 |
avs.
RA-no ventilator, bvs.
21%-0 cmH2O, and cvs. 40%-0 cmH2O
in the same parameters, P <
0.05
Conclusions: While no difference in predicting weaning outcome can be
found among 5 conditions studied, the
RSBI value measured under the condition of RA-no ventilator is the lowest. Changes in FiO2 and CPAP
settings have no effect on RSBI measured by the ventilator methods. Ventilator methods
with FiO2 21% have high incidence of adverse
reaction.