Evaluation of predictive methods for response to positive end-expiratory pressure (PEEP) in individuals with acute respiratory distress syndrome (ARDS).

Abstract

Introduction: Acute respiratory distress syndrome (ARDS) is characterized by clinical events that trigger sudden onset lung injury associated with severe refractory hypoxemia, reduced compliance and inflammatory pulmonary edema that may benefit from the use of positive end-expiratory pressure (PEEP). Lung heterogeneity associated with a reduced functional lung area (“baby lung”) requires individualized ventilatory support strategies, including occasional rescue strategies such as alveolar recruitment maneuvers(rm) in order to minimize secondary damage to the injury. ventilator-induced lung disease (VILI). The different responses to PEEP in these patients still lack consensus and therefore, understanding how to assess which patient(s) respond to PEEP variations becomes imperative in this population. Objectives: To analyze the accuracy and compare four methods for evaluating the response to PEEP described in the literature, correlating them with the clinical and mechanical characteristics of patients with ARDS. Methods: Secondary analysis study of a cohort of patients with ARDS due to. All patients with severe ARDS, ventilated in the prone position and with a PaO2/FiO2 ≤ 100 sustained for more than 120 min, were evaluated in relation to the profile of recruitability by four different methods before performing the maximal alveolar recruitment maneuver: measurement of the stress index, evaluation of the shape of the PxV curve, evaluation with the hysteresis approach and calculation of the RI-ratio. From then on, the patients were classified as “recruitable” or “non-recruitable”, following the criteria described for each of the indices, and then they were submitted to the maximum alveolar recruitment maneuver. At the end of the maneuver, the patients were evaluated regarding their response to the recruitment maneuver. Results: A total of 86 individuals of both sexes were evaluated, with a mean age of 60.92 years ± 12.18. The mean length of hospital stay was 17.43 ± 12.07 days, and the mean time of mechanical ventilation was 13.48 ± 7.8 days, with a mortality rate of 44.2% (n=38). The results confirmed previous studies and revealed that the shape of the PxV curve (AUC = 0.827 [95% CI 0.73 – 0.92]; p= 0.047), Hysteresis (AUC = 0.896 [95% CI 0.83 – 0.96; p = 0.035), and IR Ratio (AUC 0.878 [95% CI 0.80 – 0.95]; p=0.037) are accurate for evaluating the response to PEEP. However, the Stress Index presented an AUC of 0.64 with a p = 0.061 and therefore does not seem accurate in predicting the response to PEEP. Hysteresis (VCe – VCi = 378ml; GINI index = 0.792) as well as RI-ratio = 0.335; GINI index 0.756. Conclusion: The indication of the appropriate alveolar recruitment maneuver is essential to improve clinical stages and lung protection. The choice of the protection method to evaluate the response to PEEP can contribute to the reduction of morbidity and mortality and improved clinical outcomes.