Cyclic energy: the transcendental relevance of respiratory rate. A retrospective observational study with Bayesian analysis

Introduction The calculation of energy transfer in patients with acute respiratory distress syndrome (ARDS), has multiple interpretations and proposals. The parameters described as safe to minimize mechanical ventilator-associated lung injury (VALI) include only static values in their conception, and dynamic variables have been relegated to a secondary role. Subjects and Methods Analytical, observational, retrospective study of patients hospitalized in a respiratory intensive care unit, with a diagnosis of severe ARDS due to SARS-CoV-2 in whom mechanical ventilator management was guided by the use of esophageal catheter for the calculation of ventilatory variables. Thirty-four patients were included in this study, 23.5 % were women and the mean body mass index was 34.9 kg/m2. The primary objective was to quantify the amount of energy (Mechanical Power MP) transmitted by using multiple known equations and the secondary objective was to find the variables best associated with such energy transfer and with the severity of ARDS using Bayesian analysis. Results A mean of 22.2 days on invasive mechanical ventilation was recorded. Baseline MPGattinoni averaged 21.4 J/min, which did not change significantly at 30 minutes (7.5%) or 24 hours (- 0.4%) from baseline, despite esophageal catheter-guided management. The Bayesian analyses used to calculate the a posteriori inclusion probability showed that respiratory rate was the only variable consistently related to energy transfer, regardless of the equation used for its calculation and the chronological time at which these equations were measured [baseline MPGattinoni: (mean, 0.89; 95% Cred Interval: 0.75 to 1.02), at 30 minutes: (mean, 1.09; 95% Cred Interval: 0.68 to 1.49), at 24 hours: (mean, 0.65; 95% Cred Interval: 0.01 to 1.03)] or [baseline MPModesto: (mean, 0.1; 95% Cred Interval: 0.09 to 0.1), at 30 minutes: (mean, 0.1; 95% Cred Interval: 0.09 to 0.1), at 24 hours: (mean, 0.1; 95% Cred Interval: 0.09 to 0.1)]. Conclusions In severe ARDS, it is essential to minimize VALI. The calculation of energy transfer, regardless of the equation used, should always be a dynamic objective to be measured. Respiratory rate is probably the most relevant dynamic variable in the genesis of VALI. Keywords: mechanical power, elastic power, respiratory rate, ARDS, COVID-19