Determination of the Utility of Parasternal Intercostal Muscle Activity in Critically Ill Patients as a Predictor of Weaning Failure and its Association with Weaning-induced Pulmonary Edema

Introduction: Of the extradiaphragmatic muscles, the parasternal intercostal muscles are major muscles that aid in breathing when the diaphragmatic muscles are fatigued. This study was conducted to determine the activity of the parasternal intercostal muscle activity during weaning and its association with weaning-induced pulmonary edema (WIPO). The objectives were to determine the parasternal muscle thickening fraction (PTF%) in patients undergoing spontaneous breathing trials (SBTs), its association with WIPO, and to assess the risk factors associated with increased PTF%. Methods: A prospective observational study was conducted on critically ill patients admitted to a tertiary care hospital and ready to undergo weaning from mechanical ventilation (MV). The ultrasound examination for evaluation of WIPO was done along with echocardiography before and after 30 min of SBT, and the parasternal and diaphragmatic muscle evaluation was performed after 30 min of SBT. The primary outcome was weaning failure, and secondary outcomes were the presence of WIPO. Results: One hundred and thirty patients underwent a weaning trial, and 90 (69%) patients had weaning success, and 40 (31%) patients had failure. (PTF%) >10% had good discriminating capacity to predict weaning failure (area under the curve = 0.798, 95% confidence interval [CI] [0.715–0.881], P < 0.001, sensitivity 60%, and specificity 84%). PTF% ≥10%, diaphragm thickening fraction (DTF%) <21%, and diastolic dysfunction were independent predictors of WIPO ( P < 0.001). The risk factors associated with increased PTF% >10% are MV days ≥5 days before SBT and DTF% <27%. Conclusions: The PTF% is simple and accessible during ultrasound examination and has good predictive capacity to determine weaning failure and presence of WIPO in patients receiving MV.