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Year : 2018  |  Volume : 62  |  Issue : 10  |  Page : 814-815  

Extubation success can be better predicted by diaphragmatic excursion using ultrasound compared to rapid shallow breathing index


Department of Anaesthesia, Khoo Teck Puat Hospital, Singapore

Date of Web Publication9-Oct-2018

Correspondence Address:
Dr. Shahla Siddiqui
Department of Anaesthesia, Khoo Teck Puat Hospital
Singapore
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ija.IJA_428_18

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How to cite this article:
Ramakrishnan P, Siddiqui S. Extubation success can be better predicted by diaphragmatic excursion using ultrasound compared to rapid shallow breathing index. Indian J Anaesth 2018;62:814-5

How to cite this URL:
Ramakrishnan P, Siddiqui S. Extubation success can be better predicted by diaphragmatic excursion using ultrasound compared to rapid shallow breathing index. Indian J Anaesth [serial online] 2018 [cited 2018 Oct 20];62:814-5. Available from: http://www.ijaweb.org/text.asp?2018/62/10/814/242892




   Introduction Top


Mechanical ventilation is one of the cornerstones of ICU care and can change the outcome of critically ill patients.[1] Old age, prolonged ICU stay as well as critical illness myopathy and neuropathy due to the aforementioned factors compounded by the use of steroids or muscle relaxants can contribute to chances of extubation failure.[2] A rapid shallow breathing index (RSBI) of >105 is indicative of a high respiratory frequency and shallow breaths, or reduced tidal volumes, and maybe a predictor of unsuccessful extubation.[3] In a previous study, a change in diaphragmatic thickness of >30% had a positive predictive value of 91% for predicting successful extubation.[3],[4],[5] Our aim was to do a pilot study to compare diaphragmatic excursion by use of a point-of-care ultrasound by an ICU clinician who is proficient in the use of ultrasound to RSBI in predicting extubation success.


   Methods Top


Our study was a prospective, observational, comparative cohort study. Institutional Review Board approval was obtained for this study (for the use and recording of the diaphragmatic ultrasound) and informed consent was obtained from the family members and the patient post-extubation. A small predetermined sample size of 20 was used as a pilot to find a positive trend for use in a larger study thereafter. All patients received spontaneous breathing trials before extubation and were assessed for extubation by the ICU team prior to the study. An RSBI of >105 was predictive of poor chances of extubation success, and these patients were automatically excluded as they were not chosen for extubation by the ICU team at that point. Patients who had spinal, neurological, or diaphragmatic injury were excluded as this could hamper their diaphragmatic excursions. All patients could follow breathing commands on nil or minimal sedation in a semi-recumbent position. Extubation success was deemed to be as a lack of need for invasive or noninvasive ventilator support at 48 h. The zone of diaphragmatic apposition to the rib cage at the anterior axillary line in the right 8th intercostal space was used for identifying the diaphragm in all cases. It is technically difficult to visualise the left side due to the presence of the spleen. The patient was encouraged to take three or four vital capacity breaths. Since we were not timing the excursion to the breathing cycle in order for the clinician to complete the study successfully and easily, an average excursion of >1.5 cm at any point in the vital capacity breath was chosen as indicative of predictive of successful extubation.


   Results Top


Twenty observations on 20 patients were made. The ICU clinician practiced on three patients prior to the start of the study to achieve the learning curve of this strategy of identifying the diaphragm. The average age of the patients was 52 years and ranged from 21 to 89 years. 14 males and 6 female patients were recruited. The average length of stay was 5.5 days ranging from 1 to 14 days. The average RSBI was 40 (SD 17.0170), whilst the average excursion of the diaphragm was 1.98 cm (SD 0.47958). Univariate logistic regressions were performed to examine the effect of diaphragmatic excursion and RSBI on the likelihood of extubation failure. The odds of extubation success increased by 249.8 times (95% CI = {1.33, 46801}, P value = 0.039), and for an increase by 1 in RSBI, the odds of extubation failure increased by 1.008 times (95% CI = [0.94, 1.08], P value = 0.82).

As shown in [Figure 1] and [Figure 2], the modelled predictions of diaphragmatic excursion and RSBI are also compared using the area under the curve (AUC) from the ROC curves. A larger AUC indicates a higher predictive power of model. The diaphragmatic excursion model yields a larger AUC 0.92 (95% CI = [0.77, 1.0]) than the RSBI model with AUC 0.58 (95% CI = [0.27, 0.89]).
Figure 1: ROC curve for diaphragmatic excursion

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Figure 2: ROC curve for RSBI

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   Discussion Top


Evaluating diaphragmatic thickness and change with respiration is operator dependent and can lead to inaccurate results. Such studies have been done by experts in the field of ICU ultrasonography and require a fair deal of expertise. The odds ratio ranges for confidence intervals are wide probably due to the small sample size. From the results of this small pilot study, it seems that diaphragmatic excursion as evaluated by a point-of-care ultrasound is probably better in predicting extubation success than RSBI; however, bigger sample sizes are needed for verifying this result.

Acknowledgement

We acknowledge the contributions of Ms. Jiexun Wang and Mr Robin Choo for helping us with the statistics.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Wunsch H, Wagner J, Herlim M, Chong DH, Kramer AA, Halpern SD, et al. ICU occupancy and mechanical ventilator use in the United States. Crit Care Med 2013;41:2712-9.  Back to cited text no. 1
    
2.
Perren A, Previsdomini M, Llamas M, Cerutti B, Györik S, Merlani G, et al. Patients' prediction of extubation success. Intensive Care Med 2010;36:2045-52.  Back to cited text no. 2
    
3.
Fadaii A, Amini SS, Bagheri B, Taherkhanchi B. Assessment of rapid shallow breathing index as a predictor for weaning in respiratory care unit. Tanaffos 2012;11:28-31.  Back to cited text no. 3
    
4.
DiNino E, Gartman EJ, Sethi JM, McCool FD. Diaphragm ultrasound as a predictor of successful extubation from mechanical ventilation. Thorax 2014;69:423-7.  Back to cited text no. 4
    
5.
Farghaly S, Hasan AA. Diaphragm ultrasound as a new method to predict extubation outcome in mechanically ventilated patients. Aust Crit Care 2017;30:37-43.  Back to cited text no. 5
    


    Figures

  [Figure 1], [Figure 2]



 

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