Ineffective Effort in Patients With Acute Brain Injury Undergoing Invasive Mechanical Ventilation

BACKGROUND: Ineffective effort (IE) is a frequent patient-ventilator asynchrony in invasive mechanical ventilation. This study aimed to investigate the incidence of IE and to explore its relationship with respiratory drive in subjects with acute brain injury undergoing invasive mechanical ventilation.

METHODS: We retrospectively analyzed a clinical database that assessed patient-ventilator asynchrony in subjects with acute brain injury. IE was identified based on airway pressure, flow, and esophageal pressure waveforms collected at 15-min intervals 4 times daily. At the end of each data set recording, airway-occlusion pressure (P_0.1) was determined by the airway occlusion test. IE index was calculated to indicate the severity of IE. The incidence of IE in different types of brain injuries as well as its relationship with P_0.1 was determined.

RESULTS: We analyzed 852 data sets of 71 subjects with P_0.1 measured and undergoing mechanical ventilation for at least 3 d after enrollment. IE was detected in 688 (80.8%) data sets, with a median index of 2.2% (interquartile range 0.4–13.1). Severe IE (IE index ≥ 10%) was detected in 246 (28.9%) data sets. The post craniotomy for brain tumor and the stroke groups had higher median IE index and lower P_0.1 compared with the traumatic brain injury group (2.6% [0.7–9.7] vs 2.7% [0.3–21] vs 1.2% [0.1–8.5], P = .002; 1.4 [1–2] cm H₂O vs 1.5 [1–2.2] cm H₂O vs 1.8 [1.1–2.8] cm H₂O, P = .001). Low respiratory drive (P_0.1 < 1.14 cm H₂O) was independently associated with severe IE in the expiratory phase (IEE) even after adjusting for confounding factors by logistic regression analysis (odds ratio 5.18 [95% CI 2.69–10], P < .001).

CONCLUSIONS: IE was very common in subjects with acute brain injury. Low respiratory drive was independently associated with severe IEE.