Assessment of mechanically ventilated patients intoxicated with organophosphates by a novel surface electromyographic index

Abstract Purpose We present a new electromyographic index, named Engagement of Respiratory Muscle (ERM), for assessing the level of participation of respiratory muscles during spontaneous breathing test in patients poisoned with organophosphorus compound. Methods Diaphragm and sternocleidomastoid muscles activity was recorded by surface electromyography during spontaneous breathing test. A population of 23 patients poisoned with organophosphates and mechanically ventilated, and a control group of 28 healthy subjects were analyzed. Results All patients developed respiratory failure and 48% were diagnosed with intermediate syndrome by medical staff. The ERM index classified the patients in three clusters ( p -value < 0.005): Cluster I presented more engagement of the sternocleidomastoid compared to diaphragm, Cluster II had low muscle engagement of both muscles and also muscle weakness, Cluster III were characterized for the diaphragm recovery associated with higher engagement. The control group showed a similar muscle engagement to Cluster III . The capacity of ERM index for classifying patients with ( sensitivity ) and without ( specificity ) muscle weakness were 90.91% and 100% respectively. Conclusions The ERM is a promising index to assess the level of participation of respiratory muscle on spontaneous breathing test in patients poisoned with organophosphorus compounds, which could improve the extubation prognosis for these patients.