Effects of Non-invasive Ventilation on Function Diaphragmatic and Caval Distension

Introduction: Understanding how the applicability of non-invasive ventilation can directly affect the anatomy and diaphragmatic function, as well as the opening diameter of the inferior vena cava in healthy individuals is fundamental to knowing how this therapy can interfere with treatment results. Objective: Identify the acute effects of PEEP and ventilatory support pressure on thickening fraction, diaphragmatic mobility and vena cava distension in healthy people. Methods: This is a crossover, randomized study, blinded to the evaluator and the researcher responsible for the statistical analysis. Volunteers will undergo a NIV session, randomized into groups: CPAP, Bi-level and spontaneous breathing, without NIV support (control). The outcomes evaluated will be diaphragmatic ultrasound and inferior vena cava distensibility. The CPAP levels will be: 5, 10 and 15 cmH2O after 5 minutes of use and in the Bi-level group we will maintain the PEEP value at 5cmH2O and modify the pressure support values to the values: 5, 7 and 10 cmH2O pressure support, with all outcomes also being assessed after 5 minutes. Participants will remain in a supine position, with the right upper limb positioned behind the head, throughout the protocol and all measurements will be collected in the inspiratory and expiratory phases with volumes basal currents. For statistical analysis, intention-to-treat analysis will be employed and groups will be compared using Student's t-test, for continuous variables, or chi-square, for categorical variables. ANOVA split-plot, repeated measures for primary occurrences. Analyzes of covariance to identify differences between groups using baseline scores as covariates. Effect sizes and confidence intervals will be calculated using eta squared (η²). Expected results: Elucidate the effects of different blood pressure levels on diaphragmatic function and inferior vena cava distension.