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ORIGINAL ARTICLE
Year : 2022  |  Volume : 35  |  Issue : 2  |  Page : 672-677

Integrative weaning index as a predictor of weaning success


Department of Anesthesia, Intensive Care and Pain Management, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Date of Submission28-Nov-2021
Date of Decision25-Jan-2022
Date of Acceptance30-Jan-2022
Date of Web Publication27-Jul-2022

Correspondence Address:
Eman A Abdelsatar Abohegazy
Shebein Elkom
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_273_21

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  Abstract 


Objective
This study aimed to evaluate the power of integrative weaning index (IWI) in predicting the success rate of spontaneous breathing trial (SBT) in the mechanically ventilated patients.
Background
The use of weaning predictive indicators can avoid early extubation and wrongful prolonged mechanical ventilation. This study aimed to evaluate the effectiveness of IWI in predicting the success rate of SBT in patients under mechanical ventilation.
Patients and methods
In this prospective study, 120 patients undergoing mechanical ventilation for more than 48 h were enrolled. Before weaning initiation, the IWI was calculated and based on the defined cutoff point (≥44), the success rate of SBT was predicted. If they were in the normal range besides the patient's tolerance, the test was considered a success. The result was then compared with the IWI and further analyzed.
Results
The SBT was successful in 96 (80%) and unsuccessful in 24 (20%) cases. The difference between the true patient outcome after SBT, and the IWI prediction was 0.833 according to the Kappa agreement coefficient (P < 0.001). Moreover, regarding the predictive power, IWI had high sensitivity (96.87%), specificity (95.83%), positive and negative predictive values (98.8 and 88.5%), and accuracy (96.7%).
Conclusion
The IWI as a more objective indicator has acceptable accuracy and power for predicting the SBT result.

Keywords: index, integrative, predictor, success, ventilation, weaning


How to cite this article:
Doha NM, Attalla HA, Abohegazy EA, Alsakka AA. Integrative weaning index as a predictor of weaning success. Menoufia Med J 2022;35:672-7

How to cite this URL:
Doha NM, Attalla HA, Abohegazy EA, Alsakka AA. Integrative weaning index as a predictor of weaning success. Menoufia Med J [serial online] 2022 [cited 2024 Mar 28];35:672-7. Available from: http://www.mmj.eg.net/text.asp?2022/35/2/672/352189




  Introduction Top


Both delayed and early weaning from the mechanical ventilation device both impose serious complications to the patient and the health system. Therefore, it is recommended that weaning is done after accurate and objective assessment and when the patient is truly ready for separation from the ventilator[1]. Many predictors of weaning were reviewed and analyzed. Only eight, including the rapid shallow breathing index (RSBI), tidal volume (TV), tracheal airway occlusion pressure 0.1 s (P = 0.1), the product of P = 0.1 and f/Vt (P = 0.1×f/Vt), respiratory rate (RR) (f), static compliance of the respiratory system (Cst, rs), ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2 ratio), and the new integrative weaning index (IWI) (Cst, rs×arterial oxygen saturation/f/Vt ratio) presented significant likelihood ratios to predict the weaning outcome[2],[3].

According to the Sixth International Consensus Conference on Intensive Care Medicine, patients who meet the following satisfactory readiness criteria should be considered ready for weaning: evidence of resolution or improvement of the underlying cause for mechanical ventilation, pH more than 7.25, intact respiratory drive, hemodynamic stability without or minimal cardiovascular support, frequency to tidal volume ratio (f/Vt) or RSBI less than 105 breaths/min/l, RR (f) of 35 breaths/min or less, maximal inspiratory pressure of −20 or less to −25 cmH2O, vital capacity of more than 10 ml/kg, and arterial oxygen saturation (SaO2) above 90% with a FiO2 of 0.4 or less [or partial pressure of arterial oxygen (PaO2)/FiO2 ratio of 150 mmHg or above][4].

IWI was developed in 2009 by Nermer et al.[5]. The IWI evaluates, in a single equation, the respiratory mechanics, oxygenation, and the respiratory pattern, through the static compliance of the respiratory system (Cst rs), SaO2 and f/Vt ratio, respectively. IWI = Cst rs×SaO2/(f/TV)[4].

Several reasons concurred to the choice of the above parameters: f/Vt is considered the best[5] or one of the best indexes to evaluate the weaning outcome[3]; Cst rs is associated with a shorter time to weaning when more than 20 ml/cmH2O; and SaO2 has proven to be useful to evaluate the readiness for weaning or to indicate the weaning failure in several studies and revisions[5].

This study aimed to evaluate the power of the IWI in predicting the success rate of the spontaneous breathing trial (SBT) in the mechanically ventilated patients.


  Patients and methods Top


This prospective study was conducted in the ICU, Faculty of Medicine, Menoufia University. The study included 120 mechanically ventilated patients. The sample size was calculated based on the results of Boniatti and Viviane. The SD of extubation failure after 30 min of the modified IWI was 49.7 to achieve a power of 80% and 0.5 alpha one error. The calculated sample should be 120.

The patients were weaned from mechanical ventilation using the traditional weaning indices as well as IWI. The study was approved by the local ethics committee on research involving human participants; informed consent was obtained from each individual or his first-degree relatives after proper explanation of the study procedure. Inclusion criteria: adult patients over 18 years old, who were mechanically ventilated for more than 48 h fulfilling the readiness criteria for weaning. Exclusion criteria: patients with chronic debilitating neuromuscular disease, advanced liver failure, decompensated heart failure, severe metabolic acidosis, severe electrolyte imbalance, and anatomical deformities of the vertebral column or the chest wall.

Methods

Based on the physician-in-charge's protocol, after the assessment of the above-mentioned indexes regarding readiness for weaning, a SBT for 60 min should follow as a diagnostic test to determine the likelihood of successful extubation. The patients were ventilated through Drager evita XLR. The patients were placed on the spontaneous mode with a pressure support (PS) of 8–10 cmH2O, a PEEP of 5 cmH2O, and FiO2 less than 40%. Afterward, the device's PS was changed to 0, and the RR/Vt, PaO2, Cst rs, the airway occlusion pressure (P = 0.1), and IWI were recorded. The patient's hemodynamic status and serial arterial blood gas were recorded at specific time intervals every 30 min. At the start of the SBT the patient was switched temporally to the volume control mode and a 30 s pause at the end of inspiration to measure the static compliance of the respiratory system. IWI was calculated from the given equation. At SBT, tidal volume (TV), RR, RSBI, minute ventilation, airway occlusion pressure (P = 0.1), SaO2, PO2, and PCO2 were evaluated at 0 min (t0), 30 min (t30), and 60 min (t60), as well as the IWI. In case of tolerance by the patient, the SBT result was considered as successful, and in case of any of the following results, an unsuccessful test result was recorded: Reduced SaO2 less than 90%, PaO2 less than 60 mmHg, PaCO2 more than 50 mmHg, pH less than 7.30 or more than 0.07 reduction in pH, RR more than 35/min or an increase more than 50% during 5 min, HR more than 140/min, or more than 0.20 reduction in MAP, agitation, perspiration, and reduced level of consciousness.

Statistical analysis

The statistical analysis was performed using the Standard SPSS software package, version 22 (SPSS Inc., Chicago, Illinois, USA). Normally distributed numerical data are presented as mean ± SD and differences between groups were compared using the independent Student's t test. Data not normally distributed were compared using the Mann–Whitney test and are presented as median (interquartile range), and categorical variables were analyzed using the χ2 test or Fisher's exact test and are presented as n (%). Odds ratio was used to assess the predictors for extubation. All P values are two-sided. P value less than 0.05 is considered statistically significant. Sensitivity, specificity, and cutoff values of predictors were evaluated by area under the receiver-operating characteristic (ROC) curve (area under the curve).


  Results Top


Given the SBT, among the 120 studied cases, 96 (80%) had a successful outcome whereas a failure was recorded in the other 24 (20%) patients. Among the successful cases, 53 (55.2%) were males and 43 (44.8%) females. The same figures were 11 (45.8%) and three (54.2%) in the failure group, indicating no meaningful difference between the two groups regarding sex (P = 0.410). Also, there was no statistical difference between the success and failure groups as regards age and BMI (P = 0.393 and 0.917, respectively; [Table 1]). Moreover, the findings showed a statistically meaningful difference between the two groups in terms of duration of mechanical ventilation, the simplified acute physiology score 3[6], RR, static compliance, the airway occlusion pressure (P = 0.1), RSBI, and the IWI score (P < 0.05) [Table 1],[Table 2],[Table 3].
Table 1: Demographic data and patients' characteristics (sex, age, BMI, simplified acute physiology score 3 and the duration of mechanical ventilation)

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Table 2: Statistical comparison between the two studied groups according to the conventional weaning parameters

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Table 3: Integrative weaning index at 0, 30, and 60 min of spontaneous breathing trial

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Similarly, the IWI prediction regarding the success or failure of the SBT result showed success in 100 (83.3%) and failure in 20 (16.7%) cases. The agreement between the true patients' outcome after weaning and the IWI prediction revealed a Kappa coefficient of 0.833 (P < 0.001). This means that in 83.3% of cases the IWI prediction regarding weaning was in agreement with the true SBT outcome [Table 3].

[Table 4] showed a correlation between the IWI and the conventional weaning parameters. The IWI predictive power showed a sensitivity of 96.87% for this index. It means that before weaning the IWI has correctly predicted the success of SBT in 96.87% of those with a true successful outcome. RSBI had a sensitivity of 98.96%, specificity of 100%, positive predictive value (PPV) of 100%, negative predictive value (NPV) of 96%, and a diagnostic accuracy of 99.2% with a P value less than 0.001. P value of 0.1 had a sensitivity of 93.75%, specificity of 100%, PPV of 100%, NPV of 80%, and a diagnostic accuracy of 95.0% with a P value less than 0.001. Static compliance had a sensitivity of 96.8%, specificity of 58.3%, PPV of 90.3%, NPV of 82.4%, and a diagnostic accuracy of 89.16% with a P value less than 0.001. Moreover, PO2 had a sensitivity of 67.71%, specificity of 50%, PPV of 84.4%, NPV of 20.7%, and a diagnostic accuracy of 64.17%. Minute ventilation had a sensitivity of 90.62%, specificity of 33.33%, PPV of 84.5%, NPV of 47.1%, and a diagnostic accuracy of 79.16% with a P value more than 0.05. According to the ROC curve, the value for 95% sensitivity and specificity of the weaning parameters were 44 ml/cmH2O breaths/min/l for IWI, 70 breaths/min/l for RSBI, 2.2 Mbar for P = 0.1, 7.1 for minute ventilation, 32 ml/cmH2O for static compliance, and 140 mmHg for PO2.
Table 4: Validity (area under the curve, sensitivity, and specificity) for integrative weaning index and other conventional weaning parameters

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  Discussion Top


Weaning patients from mechanical ventilation remains a debatable and cumbersome issue and may occupy up to 40% of the patient's total ventilation time. Thus, extubation and weaning periods continue to be one of the most challenging aspects for intensive care teams[7].

This study aimed to evaluate the power of the IWI in predicting the success rate of SBT in mechanically ventilated patients.

Among all patients, SBT succeeded in 96 (80%) and failed in 24 (20%) of cases. This is consistent with the study by Eskandar and Apostolakos[8]. They concluded that despite all the medical treatments and care offered to patients receiving mechanical ventilation for over 24 h, the first attempt to wean is often a failure in almost 22% of the cases.

The findings of the current study support a significant relationship between the simplified acute physiology score 3 score, the patients' respiratory parameters, and the SBT outcome of the ventilation device, meaning that the prevalence of prolonged time of ventilation, RR, RSB (RR-tidal volume ratio), morbidity scores, and the inappropriate pulmonary compliance was higher among patients with an unsuccessful outcome.

The current study also revealed statistical significant differences between the two groups as regards the airway occlusion pressure.

Moreover, we found that there was no statistical difference between the two groups as regards baseline PO2, PaCO2, and SPO2. However, by monitoring the patients at different time intervals 30 and 60 min during SBT, there were statistically significant differences between the two groups. Our study demonstrated significant positive correlation between the IWI and the weaning success. The difference between the true patient outcome after SBT, and the IWI prediction was 0.833 according to the Kappa agreement coefficient (P < 0.001). By analysis of ROC curves, IWI had a general sensitivity of 96.87% and specificity of 95.83% with a PPV of 98.9%, NPV of 88.5%, and a diagnostic accuracy of 96.7%. The value at which the index had a sensitivity and specificity of 95% was 44 ml/cmH2O breaths/min/l.

Our results agreed with the study of Madani et al.[9],, which resulted in that IWI had high sensitivity (95.6%), specificity (40%), PPV and NPV (90.5 and 60%), positive and negative likelihood ratios (1.59 and 0.11), and accuracy (86.7%).

Also Ebrahimabadi[10] assessed the validity of IWI for discontinuation from mechanical ventilation in Iranian ICUs. It was studied in six ICU patients with different characteristics, and a sensitivity of 94.59, specificity equal to 66.67, PPV of 97.22, NPV equal to 50, positive likelihood ratio of 2.84, negative likelihood ratio equal to 0.08, and an accuracy of 92.5 were obtained; and could prove persistence of successful weaning in a 48-h period with an accuracy of more than 90%.

Also, these results are in agreement with the study by Azeredo et al.[11]. They concluded the IWI was the only respiratory variable associated with mechanical ventilation weaning success with high statistical difference (P < 0.001).

Also, our study was supported by the study of Telias et al.[12], which recommended that P = 0.1 is a reliable bedside tool to assess respiratory drive and detect potentially injurious inspiratory effort.

This is in contrast to the study of Monaco et al.[13] whose study demonstrated that the different respiratory variables including the tidal volume, minute ventilation, RR, and RSBI predict early weaning from mechanical ventilation poorly. This may be due to the small sample size of the study. The study was carried out on 73 patients.

On the other hand, the study of Boniatti et al.[14] revealed that the three modified IWI values (the first and 30th minute of the SBT and the difference between them), as well as the other ventilator parameters and extubation predictors, displayed poor extubation outcome discrimination accuracy. All the weaning indexes presented small areas under the ROC curve. This may be due to that they did not use fixed weaning criteria before SBT. Moreover, no definitive cutoff point was identified.

By analysis of the ROC curve shown in [Figure 1], sensitivity was highest for RSBI (0.986), followed closely by the IWI (0.968) and the static compliance (96.87) and the lowest for PO2 (0.677). Specificity was the highest for the RSBI (1.0), the airway occlusion pressure (1.0), IWI (0.95) and lowest for the RR (0.33), and the minute ventilation (0.33). The area under the ROC curve for the RSBI ratio was 1.0 followed by the area under the curves for the IWI (0.996) (P < 0.05), P = 0.1 (0.953, P < 0.001), and static compliance (0.759, P < 0.001).
Figure 1: ROC curve for the different weaning parameters IWI, RSBI, P=0.1, RR, static compliance, and PO2 to evaluate their performance in the weaning process. IWI, integrative weaning index; ROC, receiver-operating characteristic; RR, respiratory rate; RSBI, rapid shallow breathing index.

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This is in agreement with the study by Nemer et al.[15]. The study was conducted on 216 patients and successful weaning was observed in 183 (84.7%) patients and weaning failure in 33 (15.27%). IWI presented the highest accuracy, along with the RSBI and area under the curve, which was 0.96 × 0.85, respectively (P = 0.003), and also larger than that under the curves for the other indexes. Also, the study of Ghada El-Baradey et al.[16] recommended IWI as a strong predictor of both successful and failed weaning.

Limitations of the current study include that IWI was evaluated taking into consideration the cutoff values of other indices, especially RSBI during the weaning process, preventing its evaluation as a sole index of weaning from mechanical ventilation, particularly in patients who may not meet some of the targets of the other indices, yet might be successfully weaned otherwise.

Limitations

Limitations of the current study include that the IWI was evaluated taking into consideration the cutoff values of other indices especially RSBI during the weaning process, preventing its evaluation as a sole index of weaning from mechanical ventilation, especially in patients who may not meet some of the targets of the other indices, yet might be successfully weaned otherwise.


  Conclusions Top


The IWI as a more objective indicator has acceptable accuracy and power for predicting the SBT result. Therefore, in addition to the reliable prediction of the final weaning outcome, it has favorable power to predict if the patient is ready to breathe spontaneously as the first step to weaning. Further studies are needed to validate its performance on children.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Soran A, Chelluri L, Lee KK, Tisherman SA. Outcome and quality of life of patients with acute pancreatitis requiring intensive care. J Surg Res 2000; 91:89–94.  Back to cited text no. 1
    
2.
Hess DR, MacIntyre NR. Ventilator discontinuation: why are we still weaning?. Am Thorac Soc 2011; 184:392–394.  Back to cited text no. 2
    
3.
MacIntyre NR. Evidence-based assessments in the ventilator discontinuation process. Respir Care 2012; 57:1611–1618.  Back to cited text no. 3
    
4.
Boles JM, Bion J, Connors A, Herridge M, Marsh B, Melot C, Welte T. Weaning from mechanical ventilation. Eur Respir J 2007; 29:1033–1056.  Back to cited text no. 4
    
5.
Nemer SN, Barbas CS, Caldeira JB, Cárias TC, Santos RG, Almeida LC. A new integrative weaning index of discontinuation from mechanical ventilation. Crit Care 2009; 13:1–9.  Back to cited text no. 5
    
6.
Tobin MJ, Jubran A. Variable performance of weaning-predictor tests: role of Bayes' theorem and spectrum and test-referral bias. Intensive Care Med 2006; 32:2002–2012.  Back to cited text no. 6
    
7.
Mantha S, Ramachandran G, Prasad V. Validation of simplified acute physiology score 3 (SAPS 3), for predicting mortality in the respiratory intensive care unit. Radiology 1982; 143:29–36.  Back to cited text no. 7
    
8.
Eskandar N, Apostolakos MJ. Weaning from mechanical ventilation. Crit Care Clin 2007; 23:263–274.  Back to cited text no. 8
    
9.
Madani SJ, Saghafinia M, Sedighi Nezhad H, Ebadi A, Ghochani A, Fazel Tavasoli A. Validity of integrative weaning index of discontinuation from mechanical ventilation in Iranian ICUs. Thrita 2013; 2:62–68.  Back to cited text no. 9
    
10.
Ebrahimabadi S, Moghadam AB, Vakili M, Modanloo M, Khoddam H. Studying the power of the integrative weaning index in predicting the success rate of the spontaneous breathing trial in patients under mechanical ventilation. Indian J Crit Care Med 2017; 21:488–493.  Back to cited text no. 10
    
11.
Azeredo LM, Nemer SN, Barbas CS, Caldeira JB, Noé R, Guimarães BL. The integrative weaning index in elderly ICU subjects. Respir Care 2017; 62:333–339.  Back to cited text no. 11
    
12.
Telias I, Junhasavasdikul D, Rittayamai N, Piquilloud L, Chen L, Ferguson ND. Airway occlusion pressure as an estimate of respiratory drive and inspiratory effort during assisted ventilation. Am J Respir Crit Care Med 2020; 201:1086–1098.  Back to cited text no. 12
    
13.
Monaco F, Drummond G, Ramsay P, Servillo G, Walsh T. Do simple ventilation and gas exchange measurements predict early successful weaning from respiratory support in unselected general intensive care patients? Br J Anaesth 2010; 105:326–333.  Back to cited text no. 13
    
14.
Boniatti VM, Boniatti MM, Andrade CF, Zigiotto CC, Kaminski P, Gomes SP. The modified integrative weaning index as a predictor of extubation failure. Respir Care 2014; 59:1042–1047.  Back to cited text no. 14
    
15.
Nemer SN, Barbas CSV. Predictive parameters for weaning from mechanical ventilation. J Brasil Pneumol 2011; 37:669–679.  Back to cited text no. 15
    
16.
El-Baradey GF, El-Shmaa NS, Ganna SA. Can integrative weaning index be a routine predictor for weaning success?. Indian J Crit Care Med 2015; 19:703.  Back to cited text no. 16
    


    Figures

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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