Análise da mobilidade diafragmática e distensão de veia cava inferior durante a aplicação da pressão positiva inspiratória e expiratória em indivíduos saudáveis

Abstract

Introduction: Non-invasive ventilation (NIV) is a common approach to treating conditions such as COPD, acute pulmonary oedema, and respiratory failure, and is known to increase lung volumes and reduce the work of breathing. However, the use of positive pressure can lead to diaphragmatic atrophy and affect cardiac output, altering the distension capacity of the inferior vena cava (IVC). Ultrasonography (US) has been shown to be effective in assessing diaphragmatic and inferior vena cava function and is a valuable tool for monitoring and adjusting therapy in critical care settings. Objective: To analyse the acute effects of positive inspiratory and expiratory pressures on diaphragmatic kinetics and IVC distension in healthy individuals. Method: This is a randomised, crossover, double-blind clinical trial conducted in healthy individuals aged 18 to 50 years. Participants were randomly assigned to continuous positive airway pressure (CPAP) of 5, 10, and 15 cmH2O, or bi-level inspiratory positive airway pressure (IPAP) of 10, 12, and 15 cmH2O with positive end-expiratory pressure (PEEP) of 5 cmH2O. Diaphragm movement and IVC behaviour were assessed by ultrasonography during spontaneous breathing and the six levels of positive pressure. Data were analysed using a linear mixed model and Dunn-Sidak post-test. Results: Eighty-two volunteers were included. Diaphragmatic mobility increased in CPAP modes with pressures of 15 cmH2O and in Bi-level mode with IPAP of 10, 12, and 15 cmH2O and PEEP fixed at 5 cmH2O, compared to spontaneous breathing. A weak and non-significant positive correlation was also observed between inspiratory muscle strength, assessed by maximum inspiratory pressure, and diaphragmatic mobility. There was an increase in IVC distension compared to spontaneous breathing when administering CPAP mode at pressures of 5, 10 and 15 cmH2O, and Bi-level mode with IPAP of 10, 12 and 15 cmH2O and fixed PEEP of 5 cmH2O. When evaluating the variation in IVC diameter, no significant changes were observed. Conclusion: Positive inspiratory and expiratory pressures were sufficient to increase diaphragmatic kinetics, particularly at higher positive pressures, and were able to increase IVC diameter during both inspiration and expiration.