Objective:To investigate the prevalence and influence factors of over-assistance in brain-injured patients undergoing pressure support ventilation (PSV).Methods:Brain-injured patients with mechanical ventilation under PSV were retrospectively analyzed from June 2017 to July 2019 in the Intensive Care Unit of Beijing Tiantan Hospital. The data such as the flow, airway pressure, and esophageal pressure-time wave form were collected using the software (ICU-Lab 2.5 software package, KleisTek, Bari, Italy). The respiratory parameters such as WOB, PTP were calculated to determine whether the patient had over-assistance. Prevalence of over-assistance was counted, the relationship between over-assistance and patients’ conditions and ventilator settings. The clinical criteria for over-assistance were: PTPes<50 cmH2O·s/min (definition 1) or ineffective trigger ≥10%; or WOB<0.3 J/L or ineffective trigger ≥10% (definition 2).Results:A total of 173 data sets were collected from 71 patients receiving mechanical ventilation in PSV. According to the two definitions, the incidence of over-assistance was 53.5%(38/71) and 76.1%(54/71), respectively. There was no significant difference in the incidence of over-assistance among patients with different types of brain injury (P>0.05). According to the definition 1, over-assistance was correlated with pressure support (PS) (P<0.05). According to the definition 2, over-assistance was associated with PS, the use of analgesic and sedative drugs (all P<0.05). There were no significant difference in ICU stay, mechanical ventilation time and tracheotomy rate between over-assistance and without over-assistance patients (P>0.05).Conclusion:Brain-injured patients receiving PSV have a high incidence of over-assistance. The level of pressure support and analgesic and sedative strategies are associated with insufficient inspiratory effort indicating targeted monitoring and treatment for this specific population.
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