Study of Fatigue and Respiratory Muscle Activation in the Spontaneous Breathing Test in Tube t Versus Support Ventilation at Mechanical Ventilation Weaning: Randomized Clinical Trial
Study of Fatigue and Respiratory Muscle Activation in the Spontaneous Breathing Test in Tube t Versus Support Ventilation at Mechanical Ventilation Weaning: Randomized Clinical Trial
This study aims to evaluate respiratory muscle activation and fatigue during the mechanical ventilation weaning process using surface electromyography (sEMG). Despite various weaning methods, failure rates remain significant, necessitating objective evaluative tools. This randomized crossover clinical trial includes patients intubated for at least 24 hours who meet clinical criteria for a spontaneous breathing test (SBT). Participants will undergo two SBT methods: T-tube and Pressure Support Ventilation (PSV) at 7 cmH2O, each lasting 30 minutes and separated by a 30-minute washout period. Respiratory muscle activity will be quantified by the Root Mean Square (RMS) normalized to maximum inspiratory effort (%RMS), while muscle fatigue will be assessed through the Median Frequency (MF) of the power spectrum. The study seeks to determine which weaning method optimizes respiratory muscle performance and predicts extubation success, defined as 48 hours without ventilatory support.
This randomized crossover clinical trial aims to compare the physiological effects of two spontaneous breathing trial (SBT) methods on respiratory muscle activity and fatigue in patients undergoing mechanical ventilation weaning. Patients intubated for at least 24 hours who meet clinical stability criteria-including adequate level of consciousness (Glasgow Coma Scale ≥ 13), hemodynamic stability without high doses of vasopressors, and an inspired oxygen fraction (FiO2) ≤ 0.4 - will be eligible for the study. Upon inclusion, participants will be randomized to one of two sequences: T-piece followed by Pressure Support Ventilation (PSV), or PSV followed by T-piece. The T-piece SBT involves disconnection from the ventilator with supplemental oxygen, while the PSV SBT is performed at 7 cmH2O with PEEP between 5-8 cmH2O. Each trial lasts 30 minutes, separated by a 30-minute washout period during which the patient is returned to their initial baseline ventilator settings to ensure physiological recovery and prevent carry-over effects. Electromyographic (sEMG) data will be captured using surface electrodes placed on the external intercostal muscles following SENIAM guidelines. Signal processing includes a Butterworth band-pass filter (20-450 Hz) and a sampling rate of at least 1000 Hz. The Root Mean Square (RMS) will be used to quantify muscle activation, normalized against the maximum inspiratory effort (%RMS) obtained during maximal inspiratory pressure (MIP) maneuvers. Muscle fatigue will be analyzed through the Median Frequency (MF) of the power spectrum using Fast Fourier Transform (FFT). Following the SBTs, patients will be extubated and monitored for 48 hours to determine the extubation success rate, defined as the absence of reintubation or rescue ventilatory support.Sample Size Calculation: The sample size was calculated based on the first five individuals evaluated, considering the mean and standard deviation of the primary outcome (%RMS) between the two evaluated methods. Adopting a significance level of 5% (a [alpha] = 0.05) and a statistical power of 80% (b [beta] = 0.80), the calculation indicated a required sample of [insira aqui o número total de pacientes, ex: 19] participants. To account for possible sample losses or technical signal artifacts, an additional 10% was added to the total.Statistical Analysis: Data distribution will be assessed using the Shapiro-Wilk test. Continuous variables will be expressed as mean and standard deviation or median and interquartile range, depending on normality. To compare the %RMS and MF between the T-piece and PSV methods, a Paired T-test or Wilcoxon Signed-Rank test will be utilized. For the analysis of time points (Baseline vs. 30th minute), a Two-way ANOVA for repeated measures with Post-hoc Bonferroni will be applied to identify significant differences and potential interaction effects between the weaning method and time. Categorical data, such as extubation success rate, will be analyzed using the Chi-square test or Fisher's Exact test. A p-value < 0.05 will be considered statistically significant for all analyses, which will be performed using SPSS software.
Inclusion Criteria:
Patients will be intubated and ventilated mechanically for at least 24 hours, capable of starting the spontaneous breathing test based on the criteria recommended by the current Brazilian Recommendations on Mechanical Ventilation (Barbas, 2013), through a decision of the multiprofessional team. They should present adequate level of awareness to understand guidelines and age> 18 years.
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Exclusion Criteria:
Patients with psychomotor agitation will not be able to interpret the electromyographic data, requiring an inspired fraction of oxygen greater than 0.6, tracheostomized, peritoniostomies and thoracotomies that would not allow the electrodes to be positioned in the right pectoralis major muscle, laparotomies that would not allow the positioning of the Electrodes in the rectus abdominis muscle and those whose family members have not adhered to the informed consent form (Appendix A).
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