Comparison of the rapid shallow breathing index (RSBI) calculated under direct and indirect form on the postoperative period of cardiac surgery.

Objectives: To compare and to analyze whether the values of rapid shallow breathing index (RSBI) determined by a ventilator display and a digital ventilometer were correlated.

Methods: Twenty-two adult patients (17 males and 5 females) in the postoperative period of cardiac surgery and in mechanical ventilation were studied. Prior to the data collection, each patient was evaluated, received physical therapy, in order to promote bronchial hygiene and pulmonary reexpansion, and was positioned in elevated dorsal recumbent at 45º. After these procedures, minute ventilation (MV) and respiratory rate (RR) obtained from mechanical ventilator display and digital ventilometer were recorded. The RSBI was calculated by the ratio of RR and tidal volume (VT). Paired t-test was used to compare related variables. The intra-class correlation coefficients (ICCs) were used to measure the reproducibility of the scores.

Results: A significant difference was found between the RSBI obtained from the ventilator and by the digital ventilometer (p=0.011). A high agreement for the RSBI (ICC=0.86), for the RR (ICC=0.80) for the VT (ICC=0.79) and a moderate agreement for the MV (ICC=0.74) were observed. The p-value was <0.05 for all variables.

Conclusions: There were a significant agreement between the RSBI obtained from the ventilator display and the digital ventilometer. Article registered on the Australian New Zealand Clinical Trials Registry (ANZCTR) under the number ACTRN12610000756022.