• Paulo Henrique Xavier, FonsecaAna Carolina FernandesACFLaboratory of Pulmonary Investigation, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil., Leonardo Alves Gonçalves, Giselle Cavalho de Sousa, SilvaMariana Coelho daMCDLaboratory of Pulmonary Investigation, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil., SacramentoRaquel Ferreira de MagalhãesRFMLaboratory of Pulmonary Investigation, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil., SamaryCynthia Dos SantosCDSLaboratory of Pulmonary Investigation, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil; Department of Cardiorespiratory and Musculoskeletal Physiotherapy, Faculty of Phy, Mayck Medeiros, Fernanda Ferreira Cruz, Vera Luiza Capelozzi, Nathane Satanna Felix, Paolo Pelosi, John J Marini, Patrícia Rieken Macêdo Rocco, and Pedro Leme Silva.
• Laboratory of Pulmonary Investigation, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
• Anesthesiology. 2023 Apr 1; 138 (4): 420435420-435.

BackgroundGradually changing respiratory rate (RR) during time to reduce ventilation-induced lung injury has not been investigated. The authors hypothesized that gradual, compared with abrupt, increments in RR would mitigate ventilation-induced lung injury and that recruitment maneuver before abruptly increasing RR may prevent injurious biologic impact.MethodsTwenty-four hours after intratracheal administration of Escherichia coli lipopolysaccharide, 49 male Wistar rats were anesthetized and mechanically ventilated (tidal volume, 6 ml/kg; positive end-expiratory pressure, 3 cm H2O) with RR increase patterns as follows (n = 7 per group): (1) control 1, RR = 70 breaths/min for 2 h; (2) and (3) abrupt increases of RR for 1 and 2 h, respectively, both for 2 h; (4) shorter RR adaptation, gradually increasing RR (from 70 to 130 breaths/min during 30 min); (5) longer RR adaptation, more gradual increase in RR (from 70 to 130 breaths/min during 60 min), both for 2 h; (6) control 2, abrupt increase of RR maintained for 1 h; and (7) control 3, recruitment maneuver (continuous positive airway pressure, 30 cm H2O for 30 s) followed by control-2 protocol.ResultsAt the end of 1 h of mechanical ventilation, cumulative diffuse alveolar damage scores were lower in shorter (11.0 [8.0 to 12.0]) and longer (13.0 [11.0 to 14.0]) RR adaptation groups than in animals with abrupt increase of RR for 1 h (25.0 [22.0 to 26.0], P = 0.035 and P = 0.048, respectively) and 2 h (35.0 [32.0 to 39.0], P = 0.003 and P = 0.040, respectively); mechanical power and lung heterogeneity were lower, and alveolar integrity was higher, in the longer RR adaptation group compared with abruptly adjusted groups; markers of lung inflammation (interleukin-6), epithelial (club cell secretory protein [CC-16]) and endothelial cell damage (vascular cell adhesion molecule 1 [VCAM-1]) were higher in both abrupt groups, but not in either RR adaptation group, compared with controls. Recruitment maneuver prevented the increase in VCAM-1 and CC-16 gene expressions in the abruptly increased RR groups.ConclusionsIn mild experimental acute respiratory distress syndrome in rats, gradually increasing RR, compared with abruptly doing so, can mitigate the development of ventilation-induced lung injury. In addition, recruitment maneuver prevented the injurious biologic impact of abrupt increases in RR.Copyright © 2022, the American Society of Anesthesiologists. All Rights Reserved.

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