Leonardo Cordeiro de Souza

Evaluation of a New Index of Mechanical Ventilation Weaning The Timed Inspiratory Effort

Purpose: The performance of most indices used to predict ventilator weaning outcomes remains below expectation. The purpose of this study was to evaluate a new weaning index, the timed inspiratory effort (TIE) index, which is based on the maximal inspiratory pressure and the occlusion time required to reach it. Methods: This observational prospective study included patients undergoing mechanical ventilation. Patients ready to be weaned had their TIE index and 6 previously reported indices recorded. The primary end point was the overall predictive performance of the studied weaning indices (area under the receiver operating characteristic curves [AUCs]). The secondary end points were sensitivity, specificity, positive predictive value, and negative predictive value. P values <.05 were considered significant. Results: From the 128 initially screened patients, the 103 patients selected for the study included 45 women and 58 men (mean age 60.8 ± 19.8 years). In all, 60 patients were weaned, 43 were not weaned, and 32 died during the study period. Tracheotomy was necessary in 61 patients. The mean duration of mechanical ventilation was 17.5 ± 17.3 days. The AUC of 3 weaning predictors (the TIE index, the integrative weaning index, and the frequency-to-tidal volume [f/Vt] ratio index) was higher than the other indices. The TIE index had the largest AUC. Conclusion: The TIE index performed better than the best weaning indices used in clinical practice.

Comparison of Maximal Inspiratory Pressure, Tracheal Airway Occlusion Pressure, and Its Ratio in the Prediction of Weaning Outcome: Impact of the Use of a Digital Vacuometer and the Unidirectional Valve

OBJECTIVE: To investigate the predictive value of the maximal inspiratory pressure obtained by a digital vacuometer using a unidirectional valve (PImaxUV) as to weaning outcome, and to compare its performance with the respiratory drive using airway occlusion pressure at 0.1 second (P0.1), and P0.1/PImaxUV. METHODS: Patients on mechanical ventilation for > 24 hours who fulfilled the weaning criteria were prospectively enrolled. Measurements of PImaxUV and P0.1 were accomplished with a digital vacuometer with a unidirectional valve that allows only exhalation. Measured values were electronically recorded and stored on the digital vacuometer measurement device. Cutoff points for the used parameters were: absolute values of PImaxUV > 30 cm H2O, P0.1 < 2.3 cm H2O, and P0.1/PImaxUV < 0.10. Receiver operating characteristic curves were calculated to compare the predictive values of the indexes. RESULTS: One hundred three subjects completed the test. The areas under the receiver operating characteristic curve were 0.79 ± 0.04, 0.65 ± 0.05, and 0.74 ± 0.04 for PImaxUV, P0.1, and P0.1/PImaxUV, respectively. The area under the receiver operating characteristic curve for PImaxUV was higher than for P0.1 and P0.1/PImaxUV, but statistical significance was only found against P0.1 (P = .007). CONCLUSIONS: Every studied index had only a modest performance regarding prediction of weaning outcome. Of note, PImaxUV values obtained by digital technology using a unidirectional valve performed better than historically reported using a conventional techniques, surpassing P0.1 and P0.1/PImaxUV in this regard.

Evaluation of the inspiratory pressure using a digital vacuometer in mechanically ventilated patients: analysis of the time to achieve the inspiratory peak.

BACKGROUND: The measurement of the maximal inspiratory pressure (PImax) is of great importance in choosing the time for the start of weaning. OBJECTIVE: To measure the inspiratory pressure in mechanically ventilated patients suitable for weaning to determine the point at which the PImax is achieved within 60 seconds of observation, and analyze factors associated with PImax values. METHODS: Measurement of PImax was accomplished with a digital vacuometer with a unidirectional valve, which allows only exhalation (PImaxUV). With this technique, values are registered and stored, remaining accessible whenever necessary. All patients were on mechanical ventilation, and met the criteria recommended by the American Thoracic Society/European Respiratory Society in 2007 to undergo weaning trial. RESULTS: Eighty-four from the 87 enrolled patients completed the test. No patients reached the PImaxUV in the first 20 seconds of observation. PImaxUV was achieved between 20.1 and 40 seconds in 12 patients (14.0%), and between 40.1 and 60 seconds in 72 cases (86.0%). In a multivariate analysis model in which age, sex, days of mechanical ventilation, APACHE score, and respiratory drive (measured as airway-occlusion pressure 0.1 s after the start of inspiratory flow [P0.1]) were included, only age (P = .006) and P0.1 (P = .003) were significantly associated with the values of PImaxUV. CONCLUSIONS: Within an observation period of 60 seconds, the majority of patients reached the maximal inspiratory peak between 40.1 and 60 seconds. Older patients were found to have lower PImaxUV values, whereas higher values for P0.1 strongly correlated with higher PImaxUV values. These findings are potentially useful to improve successful weaning prediction in the future, but further studies are needed to better clarify this issue.

The timed inspiratory effort: a promising index of mechanical ventilation weaning for patients with neurologic or neuromuscular diseases.

BACKGROUND: The aim of this study was to evaluate the performance of the recently described timed inspiratory effort (TIE) index in comparison with 4 other previously reported indices as to the weaning outcome in patients with neurologic or neuromuscular disorders. METHODS: This observational prospective study included subjects undergoing weaning from mechanical ventilation. The performance of the indices was evaluated by calculation of the area under the receiver operating characteristic curves. The areas under the curve were compared using the Hanley and McNeil method. P values < .05 were considered significant. RESULTS: Seventy-two subjects (57 ± 20 y old) were selected for the study. Forty-three subjects were weaned, and 21 died during the study period. The mean duration of mechanical ventilation was 22.3 ± 19.4 d. The areas under the curve of 5 weaning predictors (TIE index, integrative weaning index, noninvasive tension-time index, maximum inspiratory pressure, and breathing frequency/tidal volume index) were significantly higher than those of the other indices. The TIE index had the largest area under the curve (0.96 ± 0.02) in comparison with the integrative weaning index (0.82 ± 0.05, P = .009), noninvasive tension-time index (0.80 ± 0.05, P = .001), maximum inspiratory pressure (0.77 ± 0.06, P = .001), and breathing frequency/tidal volume index (0.72 ± 0.06, P = .001). CONCLUSIONS: In patients with neurologic or neuromuscular impairment, the TIE index had a better performance than the best weaning indices used in clinical practice.

Índice de respiração rápida e superficial como previsor de sucesso de desmame da ventilação mecânica: utilidade clínica quando mensurado a partir de dados do ventilador

Objetivo: O uso do índice de respiração rápida e superficial (IRRS) é recomendado em UTIs como um preditor de sucesso de desmame da ventilação mecânica (VM). O objetivo deste estudo foi comparar o desempenho do IRRS quando calculado pelo método tradicional (descrito em 1991) com o do IRRS medido diretamente dos parâmetros de VM. Métodos: Estudo observacional prospectivo com pacientes em VM por mais de 24 h e candidatos ao desmame. O IRRS foi randomicamente obtido pelo mesmo examinador pelos dois métodos (com um ventilômetro e a partir dos parâmetros da tela do ventilador). Na comparação dos valores obtidos com os dois métodos, utilizamos o teste de Mann-Whitney, o teste de correlação linear de Pearson e a disposição gráfica de Bland-Altman. O desempenho dos métodos foi comparado através das áreas sob as curvas ROC. Resultados: Dos 109 pacientes selecionados (60 homens; média de idade de 62 ± 20 anos), o desmame foi bem-sucedido em 65, e 36 foram a óbito. Entre os dois métodos, a frequência respiratória, o volume corrente e o IRRS apresentaram diferenças estatisticamente significativas (p < 0,001). Entretanto, quando os dois métodos foram comparados, a concordância e o coeficiente de variação intraobservador foram de, respectivamente, 0,94 (0,92-0,96) e 11,16%. Para o propósito do estudo, foi relevante o fato de que as áreas sob as curvas ROC dos dois métodos foram semelhantes (0,81 ± 0,04 vs. 0,82 ± 0,04; p = 0,935). Conclusões: O desempenho satisfatório do IRRS como um previsor do sucesso do desmame, independentemente do método utilizado, demonstra a utilidade do método com o ventilador mecânico.

Mechanical ventilation weaning in inclusion body myositis: feasibility of isokinetic inspiratory muscle training as an adjunct therapy.

Inclusion body myositis is a rare myopathy associated with a high rate of respiratory complications. This condition usually requires prolonged mechanical ventilation and prolonged intensive care stay. The unsuccessful weaning is mainly related to respiratory muscle weakness that does not promptly respond to immunosuppressive therapy. We are reporting a case of a patient in whom the use of an inspiratory muscle-training program which started after a two-week period of mechanical ventilation was associated with a successful weaning in one week and hospital discharge after 2 subsequent weeks.

The rapid shallow breathing index as a predictor of successful mechanical ventilation weaning: clinical utility when calculated from ventilator data

ABSTRACT OBJECTIVE: The use of the rapid shallow breathing index (RSBI) is recommended in ICUs, where it is used as a predictor of mechanical ventilation (MV) weaning success. The aim of this study was to compare the performance of the RSBI calculated by the traditional method (described in 1991) with that of the RSBI calculated directly from MV parameters. METHODS: This was a prospective observational study involving patients who had been on MV for more than 24 h and were candidates for weaning. The RSBI was obtained by the same examiner using the two different methods (employing a spirometer and the parameters from the ventilator display) at random. In comparing the values obtained with the two methods, we used the Mann-Whitney test, Pearsons linear correlation test, and Bland-Altman plots. The performance of the methods was compared by evaluation of the areas under the ROC curves. RESULTS: Of the 109 selected patients (60 males; mean age, 62 ± 20 years), 65 were successfully weaned, and 36 died. There were statistically significant differences between the two methods for respiratory rate, tidal volume, and RSBI (p < 0.001 for all). However, when the two methods were compared, the concordance and the intra-observer variation coefficient were 0.94 (0.92-0.96) and 11.16%, respectively. The area under the ROC curve was similar for both methods (0.81 ± 0.04 vs. 0.82 ± 0.04; p = 0.935), which is relevant in the context of this study. CONCLUSIONS: The satisfactory performance of the RSBI as a predictor of weaning success, regardless of the method employed, demonstrates the utility of the method using the mechanical ventilator.

Inspiratory Muscle Training with Isokinetic Device to Help Ventilatory Weaning in a Patient with Guillain-Barré Syndrome by Zika Virus

Zika is an arbovirus infection mainly transmitted by the mosquito Aedes aegypti. In 2016, the burden of Zika epidemic in Brazil was significant. Patients affected by Zika virus can develop Guillain-Barre syndrome, evolving to muscle respiratory failure requiring mechanical ventilation. In this setting, delayed recovery of the muscle weakness can result in prolonged weaning, a condition that by itself is related to a high mortality rate. The study is reporting a case of a patient with Zika and Guillain-Barre syndrome who underwent an inspiratory muscle training program starting after twenty-five days of mechanical ventilation and guided by serial measurements of the timed inspiratory effort (TIE) index. The patient was successfully weaned in two weeks and discharged from the hospital 30 days after extubation.Zika is an arbovirus infection mainly transmitted by the mosquito Aedes aegypti. In 2016, the burden of Zika epidemic in Brazil was significant. Patients affected by Zika virus can develop Guillain-Barré syndrome, evolving to muscle respiratory failure requiring mechanical ventilation. In this setting, delayed recovery of the muscle weakness can result in prolonged weaning, a condition that by itself is related to a high mortality rate. The study is reporting a case of a patient with Zika and Guillain-Barré syndrome who underwent an inspiratory muscle training program starting after twenty-five days of mechanical ventilation and guided by serial measurements of the timed inspiratory effort (TIE) index. The patient was successfully weaned in two weeks and discharged from the hospital 30 days after extubation.