Background and Goal of Study: The integrated pulmonary index (IPI) merges four vital parameters including end-tidal CO2, respiratory rate, pulse rate, and SpO2, as measured by capnography and pulse oximetry, into a single index value . The aim of this study was to explore the role of IPI during the weaning from mechanical ventilation after off-pump coronary artery bypass grafting (OPCAB).
Materials and Methods: Seventy-two adult patients after elective OPCAB were enrolled into a prospective study and randomized to four groups. Three groups received the postoperative recruitment maneuver (RM): 1) CPAP 40 cm H2O for 40 sec, 2) PEEP of 15 cm H2O for 5 minutes, 3) increased tidal volume for 40 sec to provide peak pressure of 40 cm H2O during inspiration. In addition, we had the control group without RM. During the RM and throughout 12 hrs of the postoperative period, all the patients were closely monitored with ECG, invasive arterial pressure and blood gases while all the components of IPI were registered with portable oximeter/capnograph (Capnostream 20, Oridion, Israel). The postoperative respiratory support was discontinued according to the weaning protocol. Data are presented as median (25th-75th percentiles) and analyzed using non-parametric statistical methods. A p value below 0.05 was regarded as statistically significant.
Results and Discussion: We found no baseline differences in the studied parameters between the groups. The IPI values did not differ significantly between the RM groups throughout the study period. The baseline IPI correlated with the duration of the postoperative respiratory support (rho=-0.27, p=0.03, n=64). As compared to the control group, the duration of mechanical ventilation after OPCAB was shorter in the PEEP 15 RM group: 160 (123-225) min vs. 218 (167-308) min, respectively (p=0.017). The IPI values at 12 hrs after extubation correlated negatively with the body mass index (rho=-0.37, p=0.008, n=52).
Conclusion(s): The integrated pulmonary index (IPI) may predict the duration of postoperative mechanical ventilation and may be a valuable adjunct to the bundle of postoperative monitoring after OPCAB. The RM after ICU admission using PEEP 15 cm H2O for 5 minutes reduces the time of respiratory support. The obese patients may demonstrate a delayed deterioration of respiratory function.