ORIGINAL ARTICLE


https://doi.org/10.5005/jp-journals-11010-1076
Indian Journal of Respiratory Care
Volume 12 | Issue 4 | Year 2023

Yang–Tobin Index and Integrative Weaning Index as Predictors of Successful Weaning from Mechanical Ventilation in Intensive Care Unit


Hemanth Mellahally Shivaraja1https://orcid.org/0009-0006-6893-8793, Jyothi Chakrabarty2, Sunil Ravindranath3https://orcid.org/0000-0003-4022-1492, Margiben T Bhatt4https://orcid.org/0000-0002-8966-1096, Aarohi H Mitra5

1Department of Critical Care, Manipal Hospitals, Bengaluru, Karnataka, India

2Department of Medical Surgical Nursing, Manipal College of Nursing, Manipal Academy of Higher Education (MAHE) (Deemed to be University), Manipal, Karnataka, India

3,4Department of Critical Care, Kasturba Medical College and Hospital, Manipal Academy of Higher Education, Manipal, Karnataka, India

5Department of Community Medicine, BJ Medical College, Ahmedabad, Gujarat, India

Corresponding Author: Margiben T Bhatt, Department of Critical Care, Kasturba Medical College and Hospital, Manipal Academy of Higher Education, Manipal, Karnataka, India, Phone: +91 8980025142, e-mail: drmargibhatt@hotmail.com

Received: 19 August 2023; Accepted: 26 November 2023; Published on: 18 January 2024

ABSTRACT

Background: Weaning is the process of liberating the patient from mechanical ventilation. It has been shown that no single weaning index can accurately predict a successful weaning process. Weaning by intensive care physicians’ bedside clinical discretion alone can sometimes lead to extubation failure. Yang–Tobin index, also known as the rapid shallow breathing index (RSBI) and integrative weaning index (IWI), are two of the most commonly used weaning indices in intensive care units (ICUs). We did a comparative study between the two indices for the prediction of successful weaning in mechanically ventilated patients.

Materials and methods: We studied 115 patients who were mechanically ventilated for >48 hours and were ready for extubation. We recorded RSBI and IWI at 60 and 120 minutes for all patients, along with other physiological parameters like sequential organ failure assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, age, and mechanical ventilator parameters. The receiver operating characteristic (ROC) curves were calculated to evaluate the predictive performance of both the indexes.

Results: We used two different indices (RSBI vs IWI) to predict successful extubation. An RSBI score of 25 was successfully extubated. Of 10 patients who experienced weaning failure and required reintubation within 48 hours, all patients had an IWI of <24. IWI was useful in detecting those patients who passed the spontaneous breathing trial (SBT) but needed reintubation afterward.

Conclusion: Results showed both the Yang–Tobin index and IWI can successfully predict the weaning outcomes from the mechanically ventilated patient. The area under the curve (AUC) for the ROC curve for both indices was almost similar, suggesting both are comparable. IWI was useful in detecting those patients who passed the SBT but needed reintubation afterward.

How to cite this article: Shivaraja HM, Chakrabarty J, Ravindranath S, et al. Yang–Tobin Index and Integrative Weaning Index as Predictors of Successful Weaning from Mechanical Ventilation in Intensive Care Unit. Indian J Respir Care 2023;12(4):315–319.

Source of support: Nil

Conflict of interest: None

Keywords: Extubation, Integrative weaning index, Mechanical ventilation, Rapid shallow breathing index, Weaning

INTRODUCTION

Mechanical ventilation, when timely initiated, can be lifesaving in intensive care units (ICU). Weaning from the mechanical ventilator is one of the most important factors that affect patient outcomes. The decision to wean from mechanical ventilation and extubation should be based on objective indices apart from bedside clinical judgment. There are a few criteria for assessing the readiness of weaning: total respiratory rate to tidal volume ratio of <105 breaths/minute/L, the total frequency of respiration <35 breaths/minute, maximal inspiratory pressure of <25 cm H2O, vital capacity >10 mL/kg, tidal volume achieved >5 mL/kg and arterial oxygen saturation (SaO2) above 90% with fraction of inspired oxygen (FiO2) of 0.4 or less. Once the readiness has been established, a spontaneous breathing trial (SBT) should be initiated to assess the likelihood of successful extubation.1,2 The reasons for reintubation and weaning failure other than primary lung conditions are many, such as untreated and severe progressive primary disease, fluid overload, congestive heart failure, poor neurological status, respiratory muscle weakness, etc. Prolonged weaning is associated with poor outcomes for patients, which results in complications exclusively associated with invasive mechanical ventilation like pneumonia, ventilator-induced lung injury, diaphragmatic dysfunction, etc. In a resource-limited setting, early weaning and extubation are helpful in reducing the cost as well as the incidence of ventilator-associated complications.3,5

No single weaning predictive index can be ideal in predicting the weaning failure6. However, we have plenty of predictors of weaning that are helpful in deciding whether the patient is ready for weaning or not.7 Systemic reviews by MacIntyre8 and Tobin and Jubran9 have analyzed 66 predictors, out of which only eight, including rapid shallow breathing index (RSBI), were significantly associated with successful weaning outcomes. Approximately, 22 studies have evaluated the predicting ability of RSBI and found that it was one of the most useful of all the predictors. Yang and Tobin proposed that the terms Yang–Tobin index and RSBI can be used interchangeably. RSBI <105 breaths/minute/L is associated with weaning success.10,11 Nemer et al.12 proposed a waning index called integrative weaning index (IWI), combining parameters like respiratory system compliance (Cst), respiratory system resistance (Rs), SaO2, and RSBI itself. IWI = Cst, Rs × SaO2 RSBI mL cm H2O breath/minute/L. We aimed to compare the Yang–Tobin index and IWI in predicting weaning success.

MATERIALS AND METHODS

This prospective observational study was conducted in a tertiary care teaching institute with 32-bed multidisciplinary ICUs over a period of 1 year. The inclusion criteria were patients above 18 years of age who required mechanical ventilation for >48 hours and were admitted to the ICU. The exclusion criteria were: (1) patients with advanced disease are less likely to survive in the same admission; (2) patients with tracheostomy tubes; and (3) patients with neuromuscular illness. In the study by Nemer et al.,12 from a total population of approximately 300 patients, weaning failure was observed in approximately 16% of patients. Considering a 95% confidence interval (CI), a 7% margin of error, and a 10% dropout rate, the sample size was calculated as 115 patients who were included in the study. Institutional Ethics Committee clearance was obtained (IEC: 876/2020, CTRI/2021/02/031137). Informed consent was obtained from patients’ next kin family members. All the procedures performed involving human subjects were in line with the Declaration of Helsinki.

Data Collection

A total of 115 patients were included in the study. Baseline data, such as the presenting complaint, age, sex, comorbidities, vital signs, main causes of respiratory failure, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, sequential organ failure assessment (SOFA) score, and days of mechanical ventilation, were documented. Mechanical ventilation-related settings like expiratory tidal volume (VT), positive end-expiratory pressure (PEEP), SaO2, and other indicators of arterial blood gas analysis were recorded for each patient. Patients ready for weaning were put on SBT for a total of 120 minutes, during which FiO2 was fixed at 35%, support pressure kept ≤10 cm H2O, and the PEEP was set at ≤5 cm H2O. Successful weaning was documented when the patient did not require reintubation or any other ventilatory support for the next 48 hours.

Weaning indices such as the Yang–Tobin index and IWI were calculated at 60 minutes and 120 minutes of SBT. RSBI was calculated as total respiratory frequency divided by tidal volume in liters, f/TV. IWI is a composite parameter of static compliance of the respiratory system (Cst, Rs), SaO2, and RSBI: IWI = Cst, Rs × SaO2/RSBI with unit mL/cm H2O breath/minute/L. An oxygen concentration of 0.35 was fixed before calculating indices as it will affect the calculation of the index as per the formula.

Statistical Analysis

We have used Statistical Package for the Social Sciences 13.0 software for general data analysis and Medcalc 11.4 software for receiver operating characteristic curve (ROC) curve analysis. Descriptive data were presented in the form of frequency and percentage tables. The area under the curve (AUC) was used for comparison of the two parameters in predicting the ability of successful weaning. A value of p < 0.05 was considered statistically significant.

RESULTS

General Data

The physiological data, as presented in Table 1, suggested that 68 (59.1%) participants were male and >50 years old. A total of 58 (50.4%) participants had primarily respiratory problems. Values of weaning indices, Yang–Tobin index, and IWI at the end of SBTs of 60 and 120 minutes were presented in Table 2. Out of 115 of the total patients, 105 (91.3%) patients had successful extubation, and 10 (8.7%) patients got reintubated within 48 hours of extubation (Fig. 1).

Table 1: General data
Frequency (n) Percentage (%)
Age
 <50 years 47 40.9
 >50 years 68 59.1
 Apache II score 21.1 40%
Gender
 Male 68 59.1
 Female 47 40.9
Reason for ICU admission
 Cardiovascular 17 14.8
 Gastrointestinal 9 7.9
 Intentional self-harm 8 7
 Respiratory 58 50.4
 Renal 10 8.7
 Polytrauma 13 11.3
Comorbid conditions
 Cardiovascular 14 12.2
 Respiratory 26 22.6
 Gastrointestinal 24 1.7
 Endocrine 54 47
 Others 19 16.5
Reintubation within 48 hours
 Yes 10 8.7
 No 105 91.3
Table 2: Comparison of RSBI and IWI in predicting successful extubation—no significant difference was found in RSBI score as well as in IWI score either at 60 or at 120 minutes
Successful extubation
No Yes
Mean SD Mean SD p-value
RSBI at 60 minutes 64 21 52 19 0.049
RSBI at 120 minutes 61 20 50 17 0.047
IWI at 60 minutes 31 12 42 19 0.07
IWI at 120 minutes 32 17 44 19 0.06

Fig. 1: Percentage of successful extubation

Comparison of RSBI and IWI

Yang–Tobin index and IWI were calculated at 60 and 120 minutes of SBT. RSBI values at 60 and 120 minutes were 64 ± 21.2 [mean ± standard deviation (SD)] and 61.4 ± 21.2 (mean ± SD), respectively, in those who had unsuccessful extubation. RSBI and IWI were compared at 60 minutes and 120 minutes to predict successful extubation, but no significant difference was found either at 60 or 120 minutes, as depicted in Table 2.

Sensitivity and specificity for RSBI and IWI for successful extubation prediction:

  • For RSBI at 60 and 120 minutes, the sensitivity for predicting the success of the weaning was 0.92 and 0.91, respectively, and the specificity was 0.5 and 0.0, respectively. The AUC of the ROC of RSBI was 0.686 (95% CI: 0.532–0.840) and 0.692 (95% CI: 0.525–0.858). Sensitivity for IWI in predicting successful weaning at 60 and 120 minutes was 0.87 and 0.91, respectively, and specificity was 0.5 at both 60 and 120 minutes. The AUC of the ROC of IWI at 60 and 120 minutes was 0.724 (0.556–0.937) and 0.748 (0.559–0.937), respectively (Table 3; Figs 2 and 3).

Table 3: Sensitivity and specificity of both the index as a predictor of successful weaning—no major difference in both the parameters
95% CI
Test result variable (s) AUC Lower bound Upper bound Sensitivity Specificity
RSBI at 60 minutes 0.686 0.532 0.840 0.92 0.5
RSBI at 120 minutes 0.692 0.525 0.858 0.91 0.0
IWI at 60 minutes 0.724 0.556 0.892 0.87 0.5
IWI at 120 minutes 0.748 0.559 0.937 0.91 0.5

Fig. 2: Receiver operating characteristic (ROC) curve for Yang–Tobin index or RSBI

Fig. 3: Receiver operating characteristic (ROC) curve for IWI

DISCUSSION

Successful weaning from mechanical ventilation requires good clinical judgment and a thorough examination of the patients. Clinical judgment alone for successful prediction of weaning is not always correct. These difficult weaning scenarios mandate the use of objective weaning indices. There are many weaning indices available to be used at the bedside. Not many indices are easy to measure and feasible in resource-limited settings. The quest for a better index that can predict successful weaning has been ever-evolving. SBT shows a positive weaning predictive value of 85%, but 15% of the patients who could finish SBT required reintubation in the next 48 hours.7,13,14 Frutos-Vivar et al.15 did a study in which 121 of the 900 patients (13.4%) who could complete SBT had an extubation failure.

Among the clinical parameters used commonly for weaning, the respiratory rate/VT ratio, that is, the Yang–Tobin index, positive fluid balance a day before extubation, and severe pneumonia from the beginning of mechanical ventilation were good predictors for weaning failure.15 This observation consolidates that along with clinical parameters, using weaning indices could be helpful while considering liberation from mechanical ventilation. RSBI of <105 was associated with weaning success. In the study by Nemer et al., while evaluating successful weaning from mechanical ventilation, 18% of the patients who completed the SBT were reintubated. IWI predicted extubation failure in nine out of 10 patients who had extubation failure. IWI was useful in detecting those who successfully cleared SBT initially but failed afterward. A higher IWI value is associated with successful prediction of extubation.

In our study, 8.7% of the patients who completed SBT were reintubated. RSBI was <105 in all patients, which means though RSBI had predicted successful extubation, they got reintubated within the next 48 hours. A total of 105 (91.3%) patients who had an IWI of >25 were successfully extubated. Interestingly, of the 10 patients who experienced weaning failure and required reintubation within 48 hours, all patients had an IWI of <24. Thus, IWI was useful for detecting those patients who passed the SBT but needed reintubation afterward. In our study, the cut-off for IWI was taken as >25 for successful prediction of weaning.

Analysis from our data suggested that the ROC curve of the RSBI was 0.682 and 0.692 at 60 and 120 minutes, respectively, which was slightly lower than most of the studies assessing the same, as the cutoff for RSBI was taken as 105 in our study. Those reported in earlier studies were between 0.77 and 0.89.16,17 The ROC curve of IWI was 0.724 and 0.748 at 60 and 120 minutes, respectively, which was marginally better than RSBI but did not yield any statistical significance when compared with the same. According to the Swets,18 AUC values suggested the following predictive ability: AUC 0.5–0.7 = low; AUC 0.7–0.9 = moderate; AUC >0.9 = high.

This study was conducted in a tertiary care academic multidisciplinary ICU with respiratory therapists and intensivists available around the clock. The doctor-to-patient ratio was 1:15. The nurse-to-patient ratio was 1:2. We had nurse practitioners in critical care available to monitor the patients. They recorded the data for the study, observing the patients postextubation for 48 hours and informing the treating physician and intensivists regarding the red flag signs of extubation failure. In India, the role of nurse practitioner critical care (NPCC) is still not well-defined. In a resource-limited setting like India, the presence of NPCC at the bedside can be of great help for treating physicians and intensivists for better monitoring of the patients. As we observed in our study, the reintubation rate was 8.7%, which was significantly lower than that of other similar studies. This can be attributed to the round-the-clock availability of nurse practitioners, critical care, respiratory therapists, and intensivists. In a resource-limited setting, even a single day, in addition to days on a mechanical ventilator and ICU length of stay, can have huge financial and clinical implications. In such cases, the routine use of such indices by nurse practitioners, critical care practitioners, or respiratory therapists for successful prediction of weaning and extubation can be extremely helpful.

Weaning is a process that has complexities when executed clinically. The weaning index should be objective and easy to calculate. There are multiple physiological and pathological factors involved in the mechanism leading to respiratory failure. Our study had a limitation in that our sample size was of a small number, and therefore, findings cannot be generalized to a mixed population of ICU patients. Weaning indices, along with point-of-care ultrasound monitoring, would have been more accurate if monitored, which was another limitation of our study. Multivariate regression analysis of the other factors associated with weaning failure in those 10 patients was not done, which is a limitation of our study.

In the current scenario, we don’t have enough evidence to use any single weaning index for the prediction of extubation failure. Multiple weaning indices should be used in combination instead of using a single parameter. In terms of future research, different ultrasound-based parameters should be analyzed along with conventional weaning indices, and multicenter large clinical trials should be conducted to assess the same. Patients’ overall prognosis, the total number of hospital lengths of stay, ICU lengths of stay, mortality, per-day costs, etc., can also be included for evaluation.

CONCLUSION

Weaning indices like the Yang–Tobin index and IWI can successfully predict the outcome of the mechanically ventilated patient. Both the indices are comparable. They should be routinely incorporated at the bedside along with other clinical parameters for successful weaning.

ORCID

Hemanth Mellahally Shivaraja https://orcid.org/0009-0006-6893-8793

Sunil Ravindranath https://orcid.org/0000-0003-4022-1492

Margiben T Bhatt https://orcid.org/0000-0002-8966-1096

REFERENCES

1. Boles JM, Bion J, Connors A, et al. Weaning from mechanical ventilation. Eur Respir J 2007;29(5):1033–1056. DOI: 10.1183/09031936.00010206

2. Girard TD, Ely EW. Protocol-driven ventilator weaning: reviewing the evidence. Clin Chest Med 2008;29(2):241–252. DOI: 10.1016/j.ccm.2008.02.004

3. Eskandar N, Apostolakos MJ. Weaning from mechanical ventilation. Crit Care Clin 2007;23(2):263–274. DOI: 10.1016/j.ccc.2006.12.002

4. Navalesi P, Bruni A, Garofalo E, et al. Weaning off mechanical ventilation: much less an art, but not yet a science. Ann Transl Med 2019;7(Suppl 8):S353. DOI: 10.21037/atm.2019.09.83

5. Schweickert WD, Gehlbach BK, Pohlman AS, et al. Daily interruption of sedative infusions and complications of critical illness in mechanically ventilated patients. Crit Care Med 2004;32(6):1272–1276. DOI: 10.1097/01.ccm.0000127263.54807.79

6. Meade M, Guyatt G, Cook D, et al. Predicting success in weaning from mechanical ventilation. Chest 2001;120(6 Suppl):400S–424S. DOI: 10.1378/chest.120.6_suppl.400s

7. MacIntyre NR, Cook DJ, Ely WE Jr, et al. Evidence-based guidelines for weaning and discontinuing ventilatory support: a collective task force facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine. Chest 2001;120(6 Suppl):375S–395S. DOI: 10.1378/chest.120.6_suppl.375s

8. MacIntyre N. Ventilator discontinuing process: evidence and guidelines. Crit Care Med 2008;36(1):329–330. DOI: 10.1097/01.CCM.0000297958.82589.E2

9. Tobin MJ, Jubran A. Meta-analysis under the spotlight: focused on a meta-analysis of ventilator weaning. Crit Care Med 2008;36(1):1–7. DOI: 10.1097/01.CCM.0000297883.04634.11

10. Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med 1991;324(21):1445–1450. DOI: 10.1056/NEJM199105233242101

11. Aboussouan LS, Lattin CD, Anne VV. Determinants of time-to-weaning in a specialized respiratory care unit. Chest 2005;128(5):3117–3126. DOI: 10.1378/chest.128.5.3117

12. Nemer SN, Barbas CS, Caldeira JB, et al. A new integrative weaning index of discontinuation from mechanical ventilation. Crit Care 2009;13(5):R152. DOI: 10.1186/cc8051

13. Ely EW, Baker AM, Dunagan DP, et al. Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med 1996;335(25):1864–1869. DOI: 10.1056/NEJM199612193352502

14. Stroetz RW, Hubmayr RD. Tidal volume maintenance during weaning with pressure support. Am J Respir Crit Care Med 1995;152(3):1034–1040. DOI: 10.1164/ajrccm.152.3.7663780

15. Frutos-Vivar F, Ferguson ND, Esteban A, et al. Risk factors for extubation failure in patients following a successful spontaneous breathing trial. Chest 2006;130(6):1664–1671. DOI: 10.1378/chest.130.6.1664

16. Delisle S, Francoeur M, Albert M, et al. Preliminary evaluation of a new index to predict the outcome of a spontaneous breathing trial. Respir Care 2011;56(10):1500–1505. DOI: 10.4187/respcare.00768

17. Epstein SK. Routine use of weaning predictors: not so fast. Crit Care 2009;13(5):197. DOI: 10.1186/cc8121

18. Swets JA. Measuring the accuracy of diagnostic systems. Science 1988;240(4857):1285–1293. DOI: 10.1126/science.3287615

________________________
© The Author(s). 2023 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and non-commercial reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.