Comparing the predicted accuracy of PO2\FIO2 ratio with rapid shallow breathing index for successful spontaneous breathing trial in Intensive Care Unit: Successful spontaneous breathing trial in ICU

Objective: To compare the predicted accuracy of PFR with RSBI for successful spontaneous breathing trial before extubation in intensive care unit.

Methods: This cross sectional study was conducted at the ICU of Ch. Pervaiz Ellahi Institute of Cardiology, Multan Medical and Nishtar Medical University Hospital from July, 2017 to January, 2019. PO2/FIO2 and RSBI was measured by a different investigator, before and 20 minutes after the start of SBT. Heart rate, blood pressure and oxygen saturation were continuously measured throughout the trial. Trial outcome was labeled as unsuccessful or successful by the investigator who was blinded to the rapid shallow breathing index and PO2/FiO2 measurements. Patients with SpO2>85%, stable hemodynamics (HR and BP change <20%), stable respiration (RR change <50%), and the absence of (i) signs of labored breathing, (ii) emergence or worsened discomfort, (iii) change in mental status, were labeled as successful in bearing the SBT. Patients were divided into two groups i.e. successful and unsuccessful, gender, Age, GOLD stage, APACHE II score, pCO2, pO2, FiO2 and RSBI score were compared between the two groups after putting all the data in SPSS version 23. Chi square tests and Student’s t-test were used on the continuous data and nominal data, accordingly. The specificity, sensitivity, diagnostic accuracy, negative predictive value and positive predictive value of two threshold values of RSBI and PO2/FiO2 ratio were calculated from the 2X2 contingency tables.

Results: RSBI threshold of 130 had 40.4% sensitivity, 51.1% specificity, 55.2% positive predictive value, 36.4% negative predictive value and 44.7% diagnostic accuracy while RSBI threshold of 105 had 94.1% sensitivity, 43.6% specificity, 71.4% positive predictive value, 83.2% negative predictive value and 73.8% diagnostic accuracy. pO2/FiO2>250 had 76.9% sensitivity, 24.5% specificity, 60.4% positive predictive value, 41.5% negative predictive value and 55.9% diagnostic accuracy.

Conclusion: Even though neither rapid shallow breathing nor the PFR was enough accurate in prediction of successful extubation but rapid shallow breathing index 105 threshold had higher sensitivity and specificity as compared to RSBI threshold 130PFR. Therefore, RSBI105 is more accurate in predicting the outcome of extubation of ICU patients.