Reverse triggering in patients with acute brain injury undergoing controlled ventilation

Reverse triggering (RT) is a ventilatory asynchrony characterized by the activation of respiratory muscles in response to passive mechanical insufflation. Although RT can potentially exacerbate lung injury, its characteristics in patients with acute brain injury remain under-explored. This study aims to elucidate the incidence and factors associated with RT in this patient population.

A retrospective analysis was conducted using a clinical database dedicated to investigating patient-ventilator asynchrony among individuals with acute brain injury. Only patients under controlled mechanical ventilation were included. RT was identified through an analysis of airway pressure, flow, and esophageal pressure waveforms collected at 15-minute intervals. The incidence of RT was determined by calculating the ratio of the number of RT breaths to the total number of breaths.

A total of 334 waveform datasets from 53 patients were analyzed. RT was observed in 8.4% of mechanical insufflations across 59 datasets (17.7%). Sixteen patients (30.2%) experienced at least one RT event. The most prevalent phenotype was mid-cycle RT (61.1%), followed by breath stacking (BD) (16.6%). Independent predictors of RT, after adjusting for confounding factors, included the combined use of opioids and sedatives, lower Sedation-Agitation Scale (SAS) scores, reduced airway delta pressure, and minimal discrepancies between the set respiratory rate and the actual respiratory rate. The pressure of occlusion at 0.1 seconds (P_0.1) demonstrated substantial predictive ability for BD, with an area under the receiver operating characteristics curve of 0.72 (95% confidence interval: 0.64-0.80, P<0.001); the optimal cutoff was determined to be 1.69 cmH₂O, achieving 83.3% sensitivity and 67.1% specificity.

Factors such as deep sedation, lower airway delta pressure, and close alignment of ventilator and patient respiratory rates were associated with RT in patients with acute brain injury. Additionally, P_0.1 served as a reliable predictor for the occurrence of BD.