Dez pontos importantes sobre a disfunção diafragmática induzida pelo ventilador: uma revisão

Abstract

Introduction: mechanical ventilation (MV) is used to assist gas exchange when the respiratory muscles are unable to maintain normal pulmonary ventilation. The use of MV can lead to contractile dysfunction and diaphragmatic atrophy. Ventilator-induced diaphragmatic dysfunction (VIDD) is defined as a diaphragmatic loss of force generating capacity induced by MV, manifesting itself as a loss of inspiratory capacity. VIDD is associated with failure in weaning and extubation and increased morbidity and mortality. Objectives: to verify which changes occur in the diaphragm when on MV, proposing measures for prevention and treatment. Rationale: there is currently no accepted standard of care for VIDD. Therefore, determining the mechanisms responsible for VIDD is a first step towards the development of effective measures for prevention and treatment. Methodology: systematic review, with works published between 2015 and 2019. Results and discussion: 35 articles were selected for the final review. We were able to conclude that VIDD comes from a conjunction of associated factors, synthesized in 16 points: (1) there is a change in contraction capacity and force generation of diaphragmatic fibers (related to MV); (2) there is a direct relationship between time spent on MV and diaphragmatic atrophy; (3) atrophy develops in patients a few days after orotracheal intubation; (4) there is a linear relationship between the level of support offered by the ventilator and the rate of atrophy; (5) the diaphragm is more sensitive to the absence of electrical and mechanical activity than other muscles; (6) in addition to atrophy, an increase in thickness (muscle edema) also increases the risk of staying longer on MV; (7) MV increases proteolysis and reduces muscle protein synthesis; (8) there is mitochondrial dysfunction, with increases in oxidative stress and ROS emission, and reduction of the concentration and activity of endogenous antioxidants; (9) in ventilation modes where diaphragmatic activation is maintained, there is protection against VIDD; (10) MV with high PEEP causes atrophy of the diaphragmatic fibers. Conclusion: Although MV provides an improvement in gas exchange and a decrease in respiratory work, it brings a series of changes that deserve attention in the context of critical patient. MV generates changes in contraction capacity and generation of strength of the diaphragm by several different mechanisms, negatively influencing the weaning process, generating greater comorbidities and lower quality of life. Despite this, some factors related to VIDD can be changed to minimize these negative effects, such as: the level of pressure support adjusted in the ventilator parameters; more precise adjustments of PEEP values; supplementation with antioxidants.