Research progress of mechanical power in ventilator-induced lung injury / 国际生物医学工程杂志

ICU acute respiratory distress syndrome has a high morbidity and mortality rate, and these patients usually need mechanical ventilation to maintain their respiratory function during treatment. However, improper setting of mechanical ventilation parameters may lead to ventilator-induced lung injury (VILI). In order to effectively prevent the occurrence of VILI, ARDSnet recommends the use of a protective ventilation strategy with low tidal volume and limited airway plateau pressure. However, from the perspective of ventilator energy transfer, VILI is actually the result of a combination of respiratory parameters such as tidal volume, airway pressure, and respiratory rate. The mechanical power well reflects the combined effect of the above parameters and is increasingly becoming a hot topic in clinical research. In this review paper, the definitions of mechanical energy and mechanical power were introduced, and the calculation methods of mechanical power under different respiratory modes are summarized. Moreover, the clinical studies related to mechanical power and VILI and further exploration of the safety threshold of mechanical power are reviewed. It is expected to provide new ideas for the future clinical development of personalized mechanical ventilation strategies and the effective prevention of VILI.

Poder mecánico como predictor de mortalidad en los pacientes con diagnóstico de neumonía por SARS-CoV-2 que recibieron ventilación mecánica invasiva / Mechanical power as a predictor of mortality in patients diagnosed with SARS-CoV-2 pneumonia who received invasive mechanical ventilation / Potência mecânica como preditor de mortalidade em pacientes diagnosticados com pneumonia por SARS-CoV-2 que receberam ventilação mecânica invasiva

Resumen: Introducción: Las fuerzas mecánicas generadas durante la ventilación mecánica por la interacción entre el ventilador y el sistema respiratorio pueden dañar al pulmón en un proceso que se ha denominado lesión inducida por el ventilador. El grado de lesión se ha relacionado con la cantidad de energía transferida desde el ventilador mecánico al sistema respiratorio dentro de un periodo de tiempo determinado, denominado poder mecánico; datos experimentales basados en tomografías sugieren que el poder mecánico mayor de 12 J/min podría generar lesión. Se proyecta como otra de las variables a controlar dentro de las estrategias de protección pulmonar, determinado en estudios experimentales como un umbral de energía a partir del cual inician los cambios mecánicos en el pulmón que pueden conducir a lesión inducida por el ventilador. Material y métodos: Se realizó un estudio retrospectivo, analítico, comparativo, se incluyeron todos los pacientes con diagnóstico de neumonía por SARS-CoV-2 que requieren ventilación mecánica invasiva; en un periodo de tiempo comprendido de marzo-agosto de 2021 que ingresaron a la Unidad de Cuidados Intensivos y utilizaron el poder mecánico como variable para predecir la mortalidad. Resultados: La población estudiada se compuso de 67 pacientes; se evaluó la asociación entre el poder mecánico alto a las 48 horas y la mortalidad, se documentó que 49.25% (n = 33) de los casos que mantuvieron el poder mecánico alto en 48 horas murieron, 28.35% (n = 19) con poder mecánico alto no se asoció con mortalidad, 8.95% (n = 6) que no mantuvieron cálculo de poder mecánico alto murieron y 13.43% (n = 9) de los pacientes con poder mecánico menor a 12 J/min no murieron. Se realizó una prueba de asociación con χ2 de Pearson en la que se obtiene un valor de p = 0.105, por lo que no existe diferencia estadísticamente significativa y no se corrobora la asociación entre la mortalidad de los pacientes con poder mecánico alto (> 12 J/min) a las 48 horas. Conclusión: El poder mecánico puede considerarse como otra variable a controlar como estrategia de protección pulmonar del paciente con infección por SARS-CoV-2, basado en que la energía transmitida al pulmón tiene mayor impacto en los pacientes que reciben ventilación mecánica por un intervalo de tiempo mayor de siete días, con un promedio de estancia en la Unidad de Cuidados Intensivos 12.3 + 6.2 días y el promedio de días de ventilación mecánica invasiva 9.2 + 5.6.

Abstract: Introduction: The mechanical forces generated during mechanical ventilation by the interaction between the ventilator and the respiratory system can damage the lung in a process that has been called ventilator induced injury. The degree of injury has been related to the amount of energy transferred from the mechanical ventilator to the respiratory system within a given period of time, called mechanical power, experimental data based on tomographies suggest that mechanical power greater than 12 J/min could generate injury. It is projected as another variables to control within lung protection strategies, determining in experimental studies as an energy threshold from which mechanical changes in the lung begin that can lead to ventilator induced injury. Material and methods: A retrospective, analytical, comparative study was carried out. All patients with a diagnosis of SARS-CoV-2 pneumonia who required invasive mechanical ventilation were admitted; In a period of time between March-August 2021, they were admitted to the intensive care unit and used mechanical power as a variable to predict mortality. Results: The studied population consisted of 67 patients; the association between high mechanical power at 48 hours and mortality was evaluated, it was documented that 49.25% (n = 33) of the patients who maintained high mechanical power in 48 hours died, 28.35% (n = 19) with power high mechanical was not associated with mortality, 8.95% (n = 6) who did not have high mechanical power calculation died and 13.43% (n = 9) of patients with mechanical power less than 12 J/min survived. An association test was performed with Pearson's χ2 in which a p value of 0.105 was obtained, so there is no statistically significant difference and the association between the mortality of the patients is not corroborated. with high mechanical power (> 12 J/min) at 48 hours. Conclusion: Mechanical power can be considered as another variable to control as a lung protection strategy for patients with SARS-CoV-2 infection, based on the fact that the energy transmitted to the lung has a greater impact on patients who receive mechanical ventilation for an interval time greater than seven days, with an average stay in the intensive care unit 12.3 + 6.2 days and the average days of invasive mechanical ventilation 9.2 + 5.6.

Resumo: Introdução: As forças mecânicas geradas durante a ventilação mecânica pela interação entre o ventilador e o sistema respiratório podem lesar o pulmão em um processo que tem sido chamado de lesão induzida pelo ventilador. O grau de lesão tem sido relacionado à quantidade de energia transferida do ventilador mecânico para o sistema respiratório em um determinado período de tempo, denominado potência mecânica. Dados experimentais baseados em tomografia sugerem que potência mecânica superior a 12 J/min pode gerar lesão. Ele é projetado como mais uma das variáveis a serem controladas dentro das estratégias de proteção pulmonar, determinando em estudos experimentais como um limiar de energia a partir do qual se iniciam as alterações mecânicas no pulmão que podem levar à lesão induzida pelo ventilador. Material e métodos: Realizou-se um estudo retrospectivo, analítico e comparativo, foram admitidos todos os pacientes com diagnóstico de pneumonia por SARS-CoV-2 que necessitaram de ventilação mecânica invasiva; em um período de março a agosto de 2021 que foram internados na unidade de terapia intensiva e utilizaram a potência mecânica como variável para predizer mortalidade. Resultados: A população do estudo foi composta por 67 pacientes; Foi avaliada a associação entre alta potência mecânica em 48 horas e mortalidade, foi documentado que 49.25% (n = 33) dos pacientes que mantiveram potência mecânica alta em 48 horas morreram, 28.35% (n = 19) com potência mecânica alta não foi associado à mortalidade, 8.95% (n = 6) que ñao mantiveran o calculo de alta potencia mecanoca morreram e 13.4% (n = 9) dos pacientes com potencia mecanica menor que 12 J/min nao morreram. Realizou-se um teste de associação com o χ2 de Pearson, no qual se obtém um valor de p de 0.105, portanto não há diferença estatisticamente significante e a associação entre mortalidade do paciente não é corroborada com alta potência mecânica (> 12 Joul/min) em 48 horas. Conclusão: A potência mecânica pode ser considerada mais uma variável a ser controlada como estratégia de proteção pulmonar para pacientes com infecção por SARS-CoV-2, tendo em vista que a energia transmitida ao pulmão tem maior impacto em pacientes que recebem ventilação mecânica por um intervalo de tempo superior a 7 dias, com média de permanência na unidade de terapia intensiva 12.3 + 6.2 dias e média de dias de ventilação mecânica invasiva 9.2 + 5.6.

Relación entre intensidad de la ventilación mecánica y agravamiento de la disfunción multiorgánica por la COVID-19 / Relationship between intensity of mechanical ventilation and multiple organ dysfunction worsening by COVID-19

RESUMEN Introducción: La intensidad de la ventilación mecánica está reflejada por la presión de conducción dinámica y el poder mecánico. Es un predictor de lesión pulmonar inducida por el ventilador y está asociada a la mortalidad. Objetivo: Determinar si existe relación entre intensidad de la ventilación mecánica y el ΔSOFA>0 (agravamiento) en los pacientes con la COVID-19 a las 72 horas después de la intubación. Material y Métodos: Grupo de estudio conformado por 35 pacientes diagnosticados con la COVID-19 que estuvieron ventilados por más de 72 horas. Se empleó la prueba de Chi cuadrado (X 2 ) o test exacto de Fisher para comparar variables cualitativas; para las cuantitativas se empleó la prueba t de Student o U de Mann-Whitney. Se realizó una Regresión Logística Binaria Simple para encontrar relación de las variables con ΔSOFA dicotomizada para ΔSOFA≤0 y ΔSOFA>0. La capacidad discriminativa de los modelos se evaluó mediante la Curva ROC. Resultados: Presentaron SOFA>0 21 pacientes (60 %). No se encontraron diferencias significativas de la Presión de Conducción entre ambos grupos (15 vs. 18, U=94.00, z= -1,795, p=0,77). Fueron buenas predictoras de ΔSOFA>0 el Poder Mecánico (OR 3,421 [95 % IC1,510 a 7,750, p=0,003]) y el Volumen Tidal (OR 1,03 [95 % IC 1,012 a 1,068], p=0,005). El Modelo Predictivo de ΔSOFA>0 en función del Poder Mecánico (AUC 0,888 [95 % IC 0,775 a 1], p<0,001) mostró una buena capacidad discriminatoria. Conclusiones: El Poder Mecánico está relacionado con el agravamiento de la disfunción multiorgánica en pacientes sometidos a ventilación mecánica por la COVID-19.

ABSTRACT Introduction: The intensity of mechanical ventilation is reflected by driving pressure and mechanical power. It is a predictor of ventilator-induced lung injury and it can be associated with mortality. Objective: To determine if there is a relationship between intensity of mechanical ventilation and ΔSOFA>0 (worsening) in patients with COVID-19 at 72 h after intubation. Material and Methods: Study group composed of 35 COVID-19 patients who were ventilated for more than 72 hours. Chi-square test (X 2 ) or Fisher's exact test was used to compare qualitative variables; Student t test or Mann-Whitney U test was employed for quantitative ones. A Simple Binary Logistic Regression Model was performed in order to find the relationship between variables and dichotomized ΔSOFA for ΔSOFA≤0 and ΔSOFA>0. The discriminatory capacity of the models was tested by using ROC Curve. Results: A total of 21 patients (60 %) presented ΔSOFA>0 (worsening). No significant differences related to Driving Pressure were found between the two groups (15 vs. 18, U=94,00, z= -1,795, p=0,77). Mechanical Power (OR 3,421 [95 % CI 1,510 a 7,750, p=0,003]) and Tidal Volume (OR 1,03 [95 % CI 1,012 a 1,068], p=0,005) were good predictors of ΔSOFA>0. The Predictive Model of ΔSOFA>0 depending on Mechanical Power (AUC 0,888 [95 % CI 0,775 a 1], p<0,001) showed a good discriminatory capacity. Conclusions: Mechanical Power is related to multi-organ dysfunction worsening in mechanically ventilated patients with COVID-19.

Asociación y valor predictivo del índice poder mecánico-distensibilidad pulmonar con días libres de ventilación mecánica en pacientes con COVID-19 en una unidad de terapia intensiva / Association and predictive value of the mechanical power-lung compliance index with free days off mechanical ventilation in patients with COVID-19 in an intensive care unit / Associação e valor preditivo do índice de potência mecânica/complacência pulmonar com dias livres de ventilação mecânica em pacientes com COVID-19 em unidade de terapia intensiva

Resumen: Introducción: El poder mecánico (PM) se asocia a mortalidad y se debe ajustar a las características pulmonares en pacientes COVID-19. Material y métodos: Estudio observacional, retrospectivo y analítico, de septiembre de 2020 a febrero de 2021. Los parámetros de ventilación y análisis de la curva ROC y modelos de regresión de Poisson para OR. Objetivo primario fue determinar la asociación entre el índice PM/Cest y días libres de ventilación mecánica (DLVM). Resultados: Se incluyeron 43 pacientes. Se dividió en sobrevivientes (n = 25, 58.1%) y no sobrevivientes (n = 18, 41.9%). Se eligió mediana de DLVM con los parámetros de VMI. El índice PM/Cest inicial ABC 0.73 [IC 95% (0.58-0.88), p = 0.008], punto de corte de 0.90 Joules/min/mL/cm H2O. La regresión multivariable de Poisson el índice PM/Cest inicial OR 0.18 [IC 95% (0.03-0.98), p = 0.047]. Discusión: Coppola y colaboradores documentaron que en pacientes con SDRA no COVID-19, el valor de PM absoluto no demostró significancia; al ajustarlo a Cest fue independiente para mortalidad. Conclusiones: El índice PM/Cest al inicio se asoció de forma significativa e independiente con DLVM en COVID-19. Punto de corte de 0.9 J/min/mL/cmH2O con mejor sensibilidad y especificidad para predecir los DLVM y esto podría reducir la mortalidad.

Abstract: Introduction: Mechanical power (MP) is associated with mortality and must be adjusted to the pulmonary characteristics in COVID-19 patients. Material and methods: Observational, retrospective, analytical study from September 2020-February 2021. Ventilation parameters and ROC curve analysis and Poisson regression models for OR. Primary objective was to determine the association between the PM/Cest index and free days of mechanical ventilation (FDMV). Results: 43 patients were included. It was divided into survivors (n = 25, 58.1%) and non-survivors (n = 18, 41.9%). Median FDMV was chosen with the IMV parameters. The initial MP/Cest index ABC 0.73 [95% CI (0.58-0.88), p = 0.008], cut-off point of 0.90 J/min/mL/cmH2O. The multivariate Poisson regression showed the initial MP/Cest index OR 0.18 [95% CI (0.03-0.98), p = 0.047]. Discussion: Coppola et al. documented in patients with non-COVID-19 ARDS, the absolute MP value did not demonstrate significance; when adjusted to Cest, it was independent for mortality. Conclusions: The MP/Cest index at baseline was significantly and independently associated with FDMV in COVID-19. Cut-off point of 0.9 J/min/mL/cmH2O with better sensitivity and specificity to predict FDMV and this could reduce mortality.

Resumo: Introdução: A potência mecânica (PM) está associada à mortalidade e deve ser ajustada para características pulmonares em pacientes com COVID-19. Material e métodos: Estudo observacional, retrospectivo, analítico de setembro de 2020 a fevereiro de 2021. Os parâmetros ventilatórios, análise da curva ROC e modelos de regressão de Poisson para OR. O objetivo primário foi determinar a associação entre o índice PM/Cest e dias livres de ventilação mecânica (DLVM). Resultados: Foram incluídos 43 pacientes. Dividiu-se em sobreviventes (n = 25, 58.1%) e não sobreviventes (n = 18, 41.9%). A mediana do DLVM foi escolhida com os parâmetros do VMI. Índice inicial PM/Cest ABC 0.73 [IC 95% (0.58-0.88), p = 0.008], ponto de corte de 0.90 J/min/mL/cmH2O. Regressão multivariável de Poisson no índice PM/Cest inicial OR 0.18 [IC 95% (0.03-0.98), p = 0.047]. Discussão: Coppola et al. documentaram em pacientes com SDRA não-COVID-19, o valor de PM absoluto não mostrou significância; quando ajustado a Cest, foi independente para mortalidade. Conclusões: O índice PM/Cest ao início se associou de maneira significativa e independentemente com DLVM na COVID-19. Ponto de corte de 0.9 J/min/mL/cmH2O com melhor sensibilidade e especificidade para predizer DLVM e isso poderia reduzir a mortalidade.

Diagnostic value of mechanical power in patients with moderate to severe acute respiratory distress syndrome: an analysis using the data from MIMIC-Ⅲ / 中华危重病急救医学

Objective:To explore the diagnostic value of mechanical power (MP) in patients with moderate to severe acute respiratory distress syndrome (ARDS) based on the Medical Information Mart for Intensive Care-Ⅲv1.4 (MIMIC-Ⅲ v1.4).Methods:The information of ARDS patients undergoing invasive mechanical ventilation for no less than 48 hours who were hospitalized at Beth Israel Deaconess Medical Center in Boston, Massachusetts from June 2001 to October 2012 in the MIMIC-Ⅲ v1.4 were collected. The demographics of patients, disease severity scores, ARDS etiology, prognostic indicators, pre-ventilation arterial blood gas analysis and respiratory parameters within 48 hours of ventilation were extracted. According to the lowest oxygenation index (PaO 2/FiO 2) before ventilation, the patients were divided into mild to moderate ARDS group (> 150 mmHg, 1 mmHg≈0.133 kPa) and moderate to severe ARDS group (≤ 150 mmHg), and the differences in baseline characteristics between the two groups were compared. The independent predictors associated with the severity of ARDS were analyzed using Logistic regression. The receiver operator characteristic curve (ROC curve) was plotted. The area under ROC curve (AUC) was calculated to evaluate the diagnostic value of MP for moderate to severe ARDS. The Youden index was used to determine the diagnostic threshold of MP for moderate to severe ARDS. According to the cut-off value of MP based on Youden index, all ARDS patients were divided into high and low MP groups. Kaplan-Meier survival curve was used to analyze the 28-day survival status of patients. Results:A total of 403 ARDS patients were enrolled in the study, including 107 subjects with mild to moderate ARDS and 296 with moderate to severe ARDS. There were significant differences in age, sequential organ failure assessment (SOFA) score, the lowest PaO 2/FiO 2 before ventilation, the last PaO 2/FiO 2 before ventilation, 28-day mortality, the length of intensive care unit (ICU) stay, duration of mechanical ventilation, lung dynamic compliance (Cdyn) in the second 24 hours of ventilation and positive end-expiratory pressure (PEEP), plateau pressure (Pplat), driving pressure (ΔP), respiratory rate (RR), lung static compliance (Cst), MP, inspired fraction of oxygen (FiO 2) within 48 hours of ventilation between the two groups. After adjusting variables such as age, SOFA score, the last PaO 2/FiO 2 before ventilation, and related respiratory mechanics parameters, multivariate Logistic regression analysis showed that higher ΔP, PEEP and MP, and lower last PaO 2/FiO 2 before ventilation were independently associated with moderate to severe ARDS [odds ratio ( OR) and 95% confidence interval (95% CI) was 1.137 (1.032-1.252), 1.333 (1.139-1.561), 1.102 (1.030-1.179), and 0.996 (0.993-0.998), respectively, all P < 0.01]. The ROC curve analysis showed that the best cut-off value of MP for the diagnosis of moderate to severe ARDS was 18.1 J/min with sensitivity of 81.42% and specificity of 60.75%, and the AUC was 0.745 (95% CI was 0.690-0.799). According to the cut-off value of MP obtained by ROC curve, all ARDS patients were divided into high MP group (> 18.1 J/min) and low MP group (≤ 18.1 J/min). The Kaplan-Meier survival curve showed that the 28-day cumulative survival rate in the high MP group was significantly lower than that in the low MP group (73.8% vs. 85.1%; Log-Rank test: χ2 = 5.660, P = 0.017). Conclusion:MP is an independent predictor of the severity of ARDS, and it can be used to diagnose moderate to severe ARDS.

Asociación de la presión de impulso y el poder mecánico ventilatorio con la mortalidad en pacientes con COVID-19 grave-crítico / Association of driving pressure and ventilatory mechanical power with mortality in patients with severe-critical COVID-19 / Associação da pressão de impulso e potência mecânica ventilatória com a mortalidade em pacientes com COVID-19 grave em estado crítico

Resumen: Introducción: Una ventilación eficiente es fundamental en COVID-19, pero se debe aplicar un presión de distensión (PD) y el poder mecánico (PM) apropiado. Objetivo: Evaluar la asociación de la presión de distensión y el poder mecánico con la mortalidad en pacientes con COVID-19 grave-crítico. Material y métodos: Estudio observacional, transversal, analítico, retrospectivo. Mediante análisis estadístico bivariado y multivariado se determinó si el DP y el PM se asocian con la mortalidad, considerando significativa una p < 0.05. Resultados: Se incluyeron 137 pacientes con COVID-19 grave-crítico, de edad media 55.8 ± 16.4 años. Las comorbilidades fueron hipertensión arterial 85 (62%), obesidad 62 (45.3%) y diabetes mellitus 50 (36.5%). La mortalidad fue de 71 (52.3%). En enfermedad grave el DP fue de 14.2 ± 5.1 cmH2O y en enfermedad crítica fue de 11.3 ± 5.0 cmH2O (p = 0.001). Los valores medios del PM con COVID-19 grave fueron 19.5 ± 19.3 J/min y en COVID-19 crítico fueron 29.1 ± 27.6 J/min (p = 0.026). El área bajo la curva (AUC) del DP para predecir mortalidad fue de 0.740 (p < 0.001) y del PM 0.569 (p = 0.171). En el análisis multivariado los factores independientemente asociados a mortalidad fueron la edad (ORa = 1.041, IC95% 1.015-1.068, p = 0.002) y el DP (ORa = 1.207, IC95% 1.101-1.322, p < 0.001). Conclusión: La presión de distensión es un predictor independiente y significativo de mortalidad en pacientes con COVID-19 grave- crítico.

Abstract: Introduction: Efficient ventilation is essential in COVID-19 but an appropriate driving pressure (DP) and mechanical power (PM) must be applied. Objective: To evaluate the association of driving pressure and mechanical power with mortality in patients with severe-critical COVID-19. Material and methods: Observational, cross-sectional, analytical, retrospective study. Through bivariate and multivariate statistical analysis, it was determined if the DP and PM are associated with mortality, considering significant a p < 0.05. Results: 137 patients with severe-critical COVID-19, mean age 55.8 ± 16.4 years, were included. The comorbidities were arterial hypertension 85 (62%), obesity 62 (45.3%) and diabetes mellitus 50 (36.5%). Mortality was 71 (52.3%). In severe illness, the DP was 14.2 ± 5.1 cmH2O and in critical illness it was 11.3 ± 5.0 cmH2O (p = 0.001). The mean PM values with severe COVID-19 were 19.5 ± 19.3 J/min and in critical COVID-19 they were 29.1 ± 27.6 J/min (p = 0.026). The AUC of DP to predict mortality was 0.740 (p < 0.001) and of PM 0.569 (p = 0.171). In the multivariate analysis, the factors independently associated with mortality were age (ORa = 1.041, CI95% 1.015-1.068, p = 0.002) and DP (ORa = 1.207, CI95% 1.101-1.322, p < 0.001). Conclusion: Driving pressure is an independent and significant predictor of mortality in patients with severe-critical COVID-19.

Resumo: Introdução: Uma ventilação eficiente é essencial no COVID-19, mas se deve ser aplicar uma driving pressure (DP) e potência mecânica (PM) apropriadas. Objetivo: Avaliar a associação da driving pressure e a potência mecânica com a mortalidade em pacientes com COVID-19 grave-crítico. Material e métodos: Estudo observacional, transversal, analítico, retrospectivo. Por meio de análise estatística bivariada e multivariada, determinou-se se o DP e PM estão associados à mortalidade, considerando significativo um p < 0.05. Resultados: Incluíram-se 137 pacientes com COVID-19 grave-crítico, com idade média de 55.8 ± 16.4 anos. As comorbidades foram hipertensão arterial 85 (62%), obesidade 62 (45.3%) e diabetes mellitus 50 (36.5%). A mortalidade foi de 71 (52.3%). Na doença grave, o DP foi de 14.2 ± 5.1 cmH2O e na doença crítica foi de 11.3 ± 5.0 cmH2O (p = 0.001). Os valores médios de PM com COVID-19 grave foram 19.5 ± 19.3 J/min e em COVID-19 crítico foram 29.1 ± 27.6 J/min (p = 0.026). A AUC de DP para predizer mortalidade foi de 0.740 (p < 0.001) e de PM 0.569 (p = 0.171). Na análise multivariada, os fatores independentemente associados à mortalidade foram idade (ORa = 1.041, IC 95% 1.015-1.068, p = 0.002) e DP (ORa = 1.207, IC 95% 1.101-1.322, p < 0.001). Conclusão: A driving pressure é um preditor independente e significativo de mortalidade em pacientes com COVID-19 grave-crítico.

Asociación del poder mecánico con la mortalidad en pacientes con COVID-19 grave / Association of mechanical power and ventilatory intensity with mortality in patients with severe COVID-19 / Associação de potência mecânica com mortalidade em pacientes com COVID-19 grave

Resumen: Introducción: el poder mecánico (PM) y la intensidad ventilatoria (IV) se han asociado con daño pulmonar inducido por ventilador. Objetivo: evaluar la asociación del poder mecánico e intensidad ventilatoria con la mortalidad en pacientes con COVID-19 grave que no recibieron vacuna. Material y métodos: estudio observacional, de cohorte, retrospectivo realizado en pacientes con COVID-19 grave. Resultados: se incluyeron 56 pacientes de edad media 57.9 ± 11.7 años (46.4% femeninos/53.6% masculinos). La IV no fue distinta entre fallecidos y supervivientes, pero sí entre el PM, que fue significativamente mayor en fallecidos. La mortalidad global fue de 60.7%, en pacientes con un PM > 15 J/min fue de 91.7% y en aquellos con un PM de 15 J/min fue 10.0 (IC95% 1.2-84.6). En el análisis multivariado, el PM continuó asociándose independiente y significativamente a mortalidad. El AUC (área debajo de la curva) del PM para predecir mortalidad fue 0.627, de la IV fue 0.527, de la puntuación APACHE fue 0.721 y de un modelo combinado de PM + APACHE-II fue 0.774. Conclusiones: un PM > 15 J/min se asoció significativamente con mayor mortalidad en pacientes con COVID-19 grave y en combinación con el puntaje APACHE II al ingreso mejoran su capacidad predictiva.

Abstract: Introduction: mechanical power (MP) and ventilatory intensity (VI) has been associated with ventilator induced lung injury (VILI). Objective: to evaluate the association between mechanical power and ventilatory intensity with mortality in severe covid-19 patients. Material and methods: observational, cohort, retrospective study conducted in patients with severe COVID-19. Results: 56 patients of mean age 57.9 ± 11.7 years (46.4% female/53.6% male) were included. The VI was not different between deceased and survivors, but it was significantly higher in the deceased between MP. Overall mortality was 60.7%, in patients with a MP > 15 J/min it was 91.7% and in those with a MP < 15 J/min on the first day it was 52.3% (p = 0.018). The RR for mortality of a MP > 15 J/min was 10.0 (95% CI 1.2-84.6). In the multivariate analysis, MP continued to be independently and significantly associated with mortality. The CUA of the MP to predict mortality was 0.627 of the VI it was 0.527 of the APACHE score it was 0.721 and of a combined model of MP + APACHE-II it was 0.774. Conclusions: a MW> 15 J/min was significantly associated with higher mortality in patients with severe COVID-19 and, in combination with the APACHE II score at admission, improves its predictive capacity.

Resumo: Introdução: a potência mecânica (PM) e a intensidade ventilatória (IV) têm sido associadas à lesão pulmonar induzida pelo ventilador. Objetivo: avaliar a associação da potência mecânica e intensidade ventilatória com mortalidade em pacientes com COVID-19 grave que não receberam vacina. Material e métodos: estudo observacional, de coorte e retrospectivo realizado em pacientes com COVID-19 grave. Resultados: foram incluídos 56 pacientes com idade média de 57.9 ± 11.7 anos (46.4% mulheres/53.6% homens). A IV não foi diferente entre falecidos e sobreviventes, mas entre PM foi significativamente maior em falecidos. A mortalidade geral foi de 60.7%, em pacientes com PM > 15 J/min foi de 91.7% e naqueles com PM 15 J/min foi de 10.0 (IC 95% 1.2-84.6). Na análise multivariada, a PM continuou independente e significativamente associada à mortalidade. A AUC (Area Under the Curve) do PM para predizer mortalidade foi de 0.627, do IV foi de 0.527, a pontuação APACHE foi de 0.721 e do modelo combinado de PM+APACHE-II foi de 0.774. Conclusões: Um PM > 15 J/min foi significativamente associado a maior mortalidade em pacientes com COVID-19 grave e, em combinação com o escore APACHE-II na admissão, melhora sua capacidade preditiva.

El poder mecánico permite predecir mortalidad en pacientes en ventilación mecánica invasiva prolongada / Mechanical power predicts mortality and ICU length of stay in patients under prolonged mechanical ventilation / A potência mecânica permite predizer a mortalidade em pacientes com ventilação mecânica invasiva prolongada

Resumen: Introducción: El poder mecánico (PM) involucra la cantidad de energía que se disipa en el parénquima pulmonar en cada ciclo respiratorio por medio de cálculos derivados de la ecuación del movimiento respiratorio. Aún no es concluyente su valor en la práctica clínica para prevenir lesión pulmonar asociada con ventilación mecánica. Material y métodos: Estudio observacional en pacientes en ventilación mecánica invasiva (VMI), con una relación PaO2/FiO2 < 200 con al menos 5 cmH2O de PEEP. Se realizaron mediciones en los días 1 y 3, utilizando las siguientes fórmulas de PM: Gattinoni = 0.098 FR Vt (Ppico-½ΔPaw); Marini = 0.098 FR Vt Paw. Resultados: En un total de 67 pacientes, utilizando ambas fórmulas, un PM elevado al tercer día se asocia con mayor mortalidad, con área bajo la curva ROC: 0.66 (IC 95% 0.52-0.79) y 0.63 (IC 95% 0.47-0.79), respectivamente. En sujetos con más de siete días de VMI se incrementó el poder estadístico de un PM elevado para predecir mortalidad al egreso, RR = 5.89 (IC 95% 0.96-36.22, p = 0.055). Discusión y conclusiones: Un PM elevado en la práctica clínica se asocia con mayor mortalidad en esta cohorte de pacientes en VMI prolongada (> 7 días). El PM es una herramienta prometedora que puede ser calculada a la cabecera del paciente.

Abstract: Introduction: Mechanical power (MP) involves the energy supplied toward the lung parenchyma at each respiratory cycle. MP reflects damage over the lung through some calculus derived from the equation of motion of the respiratory system. Material and methods: It is an observational study of patients under mechanical ventilation, with a PaO2/FiO2 ratio < 200 at PEEP ≥ 5 cmH2O. Pressure y volumes were recorded at days 1 and 3, and PM calculations were made using these formulae: Gattinoni = 0.098 FR Vt (Ppico-½ΔPaw ); Marini = 0.098 FR Vt Paw. Results: 67 patients under mechanical ventilation were analyzed by both formulae. A high MP discriminates mortality at day three, with an area under the ROC curve: 0.66 (IC 95% 0.52-0.79) and 0.63 (IC 95% 0.47-0.79), respectively. Also, a high MP by Gattinoni formula in subjects with more than seven days under mechanical ventilation, was associated to a higher mortality at hospital discharge, HR = 5.89 (IC 95% 0.96-36.22, p = 0.055). Discussion and conclusions: In this cohort, a high MP value is related to a higher mortality in patients under prolonged mechanical ventilation (> 7 days). This calculation is a promising tool, that can be calculated at patient bedside.

Resumo: Introdução: A potência mecânica (PM) envolve a quantidade de energia que se dissipa no parênquima pulmonar em cada ciclo respiratório através de cálculos derivados da equação do movimento respiratório. Seu valor na prática clínica para prevenir a lesão pulmonar associada à ventilação mecânica ainda não é conclusivo. Pacientes e métodos: Estudo observacional em pacientes com ventilação mecânica invasiva (VMI), com relação PaO2/FiO2 < 200 com pelo menos 5 cmH2O de PEEP. As medições foram realizadas nos dias 1 e 3, utilizando as seguintes fórmulas de PM: Gattinoni = 0.098 FR Vt (Ppico-½ΔPaw ); Marini = 0.098 FR Vt Paw. Resultados: Em um total de 67 pacientes utilizando ambas fórmulas, uma PM elevada no terceiro dia está associada a maior mortalidade, com uma área sob a curva ROC: 0.66 (IC 95% 0.52-0.79) e 0.63 (IC 95% 0.47-0.79), respectivamente. Em indivíduos com > 7 dias de VMI, se incrementou o poder estatístico de uma PM elevada para predizer mortalidade na alta hospitalar, RR = 5.89 (IC 95% 0.96-36.22, p = 0.055). Discussão e conclusões: A PM elevada na prática clínica está associada a maior mortalidade nesse coorte de pacientes com VMI prolongada (> 7 dias). A PM é uma ferramenta promissora que pode ser calculada na beira do leito.

The value of mechanical power to predict the potential of lung recruitment maneuvers and assess prognosis in patients with acute respiratory distress syndrome / 中华急诊医学杂志

Objective@#To investigate the value of mechanical power (MP) to predict the potential of the lung recruitment maneuver and assess prognoses in patients with acute respiratory distress syndrome (ARDS).@*Methods@#Patients with moderate-to-severe ARDS who required mechanical ventilation therapy longer than 24 hours were randomly selected April 2017 to April 2019. The lung recruitment maneuver (RM) protocol was performed according to the patient's condition, their MP, lung ultrasound score (LUS), oxygenation index (P/F), and dead volume ratio (Vd/Vt), which were monitored before the RM and one hour after the RM. The patients were divided into the lung recruitment maneuver potential positive group (RMP-P group) and lung recruitment maneuver potential negative group (RMP-N group) according to whether the variation in the patient's RM aeration score (ΔLUS) was≥5. Differences in MP between the two groups were compared and correlations between MP variation (ΔMP), aeration score variation (ΔLUS), oxygenation index variation (ΔP/F), and dead volume ratio variation (ΔVd/Vt) were analyzed. The receiver operating characteristic curve (ROC) was used to calculate the predictive value of MP for the potential of RM and the prognosis (28-day mortality) of patients with moderate or severe ARDS.@*Results@#Eighty-three patients were enrolled in the study, 45 in the RMP-P group and 38 in the RMP-N group. There was no statistical difference in the baseline levels between the two groups (P>0.05). After RM treatment, MP, LUS scores, and Vd/Vt for each patient in the two groups decreased significantly compared to the pre-RM values, whereas, the P/F increased significantly (P<0.05). The MP, LUS scores, and Vd/Vt in the RMP-P group were significantly lower than those in the RMP-N group (P<0.05), whereas there was no difference in the P/F between the two groups after RM treatment (P>0.05). The ΔMP, ΔLUS, and ΔVd/Vt in the RMP-P group were significantly higher than those in the RMP-N group (P<0.05). There was no difference in the ΔP/F between the two groups (P>0.05). There was a significant positive correlation between ΔMP and ΔLUS and ΔVd/Vt in all patients (r=0.4746, 0.3995, P<0.01) and no significant correlation withΔP/F (r=0.0314, P>0.05). The area under the ROC curves of ΔMP for predicting the potential of RM was 0.856, with a sensitivity of 91.1% and a specificity of 63.2%. The AUC of the 28-day survival status was 0.788, with a sensitivity of 84.3% and a specificity of 62.5% (P<0.05).@*Conclusions@#Mechanical power monitoring before and after RM can be used to predict the potential of the lung recruitment maneuver and assess the prognosis in patients with moderate-to-severe ARDS.

Research status of mechanical power in ventilator-induced lung injury / 中华危重病急救医学

The ventilator-induced lung injury (VILI) was centered on the "static" characteristics of the mechanical ventilation in early phases (tidal volume, plateau pressure, positive end-expiratory pressure and driving pressure). But the "dynamic" characteristics of ventilation must not be ignored (respiratory rate and flow). Mechanical energy and mechanical power (the pace of performing energy load) regarding all factor have won wide spread attention. The energy generated by mechanical ventilation is mainly used to expand respiratory system and overcome resistance, a fraction of energy acts on lung tissues probably inducing "heat" and inflammation that is related to lung injury. The review described recent conceptual advances regarding the mechanical energy and power, and the relationship with VILI, hoping to help further understanding the risk factors for VILI.

Research status of mechanical power in ventilator-induced lung injury / 中华危重病急救医学

The ventilator-induced lung injury (VILI) was centered on the "static" characteristics of the mechanical ventilation in early phases (tidal volume, plateau pressure, positive end-expiratory pressure and driving pressure). But the "dynamic" characteristics of ventilation must not be ignored (respiratory rate and flow). Mechanical energy and mechanical power (the pace of performing energy load) regarding all factor have won wide spread attention. The energy generated by mechanical ventilation is mainly used to expand respiratory system and overcome resistance, a fraction of energy acts on lung tissues probably inducing "heat" and inflammation that is related to lung injury. The review described recent conceptual advances regarding the mechanical energy and power, and the relationship with VILI, hoping to help further understanding the risk factors for VILI.

The value of mechanical power to predict the potential of lung recruitment maneuvers and assess prognosis in patients with acute respiratory distress syndrome / 中华急诊医学杂志

Objective To investigate the value of mechanical power(MP)to predict the potential of the lung recruitment maneuver and assess prognoses in patients with acute respiratory distress syndrome(ARDS).Methods Patients with moderate-to-severe ARDS who required mechanical ventilation therapy longer than 24 hours were randomly selected April 2017 to April 2019.The lung recruitment maneuver(RM)protocol was performed according to the patient's condition,their MP,lung ultrasound score(LUS),oxygenation index(PIF),and dead volume ratio(Vd/Vt),which were monitored before the RM and one hour after the RM.The patients were divided into the lung recruitment maneuver potential positive group(RMP-P group)and lung recruitment maneuver potential negative group(RMP-N group)according to whether the variation in the patient's RM aeration score(ΔLUS)was ≥ 5.Differences in MP between the two groups were compared and correlations between MP variation(Δ MP),aeration score variation(Δ LUS),oxygenation index variation(Δ P/F),and dead volume ratio variation(Δ V d/Vt)were analyzed.The receiver operating characteristic curve(ROC)was used to calculate the predictive value of MP for the potential of RM and the prognosis(28-day mortality)of patients with moderate or severe ARDS.Results Eighty-three patients were enrolled in the study,45 in the RMP-P group and 38 in the RMP-N group.There was no statistical difference in the baseline levels between the two groups(P＞0.05).After RM treatment,MP,LUS scores,and Vd/Vt for each patient in the two groups decreased significantly compared to the pre-RM values,whereas,the P/F increased significantly(P＜0.05).The MP,LUS scores,and Vd/Vt in the RMP-P group were significantly lower than those in the RMP-N group(P＜0.05),whereas there was no difference in the PIF between the two groups after RM treatment(P＞0.05).The Δ MP,Δ LUS,and Δ V d/Vt in the RMP-P group were significantly higher than those in the RMP-N group(P＜0.05).There was no difference in the Δ P/F between the two groups(P＞0.05).There was a significant positive correlation between Δ MP and Δ LUS and Δ Vd/Vt in all patients(r=0.4746,0.3995,P＜0.01)and no significant correlation with Δ P/F(r=0.0314,P＞0.05).The area under the ROC curves of Δ MP for predicting the potential of RM was 0.856,with a sensitivity of 91.1％and a specificity of 63.2％.The AUC of the 28-day survival status was 0.788,with a sensitivity of 84.3％and a specificity of 62.5％(P＜0.05).Conclusions Mechanical power monitoring before and after RM can be used to predict the potential of the lung recruitment maneuver and assess the prognosis in patients with moderate-to-severe ARDS.

Correlation analysis between mechanical power and lung ultrasound score and their evaluation of prognosis in patients with acute respiratory distress syndrome / 中华危重病急救医学

Objective To investigate the clinical correlations between mechanical power (MP) and lung ultrasound score (LUS), and analyze their evaluation value of prognosis in patients with acute respiratory distress syndrome (ARDS). Methods Patients with moderate to severe ARDS, who underwent invasive mechanical ventilation admitted to intensive care unit (ICU) of the Lianyungang Affiliated Hospital of Xuzhou Medical University from January 2017 to March 2019 were enrolled. The MP and LUS were recorded 0, 24, 48 and 72 hours after ICU admission. The patients were divided into death group and survival group according to the 28-day prognosis. The trends of MP and LUS in the two groups and their differences between groups were analyzed. Then the MP and LUS were analyzed by bivariate correlation analysis, and their correlations with acute physiology and chronic health evaluationⅡ (APACHEⅡ), sequential organ failure assessment (SOFA), oxygenation index (PaO2/FiO2), and blood lactate (Lac) were also analyzed. The predictive value of MP and LUS 0 hour and 72 hours in ICU for 28-day mortality in patients with moderate to severe ARDS was analyzed by receiver operating characteristic (ROC) curve. Results At the end, 83 patients were enrolled, with 32 died and 51 survived in 28-day. The Lac level, APACHEⅡ and SOFA in the death group were significantly higher than those in the survival group, while PaO2/FiO2 was significantly lower than the survival group, and the other baseline indicators were not statistically significant between the two groups. As the treatment time increased, the MP and LUS of the survival group showed a significant decrease trend, while the death group showed a significant upward trend. The MP and LUS of the death group 0, 24, 48, 72 hours after ICU admission were significantly higher than those of the survival group [MP (J/min): 20.97±3.34 vs. 17.20±4.71, 21.56±3.48 vs. 16.87±3.85, 22.72±2.97 vs. 16.13±3.52, 25.81±3.46 vs. 15.24±3.78; LUS: 19.17±3.31 vs. 16.27±4.28, 20.28±3.65 vs. 15.27±3.23, 21.53±4.32 vs. 13.63±3.71, 23.94±3.82 vs. 12.53±2.94, all P < 0.05]. There was a significant positive correlation between MP and LUS 0, 24, 48, 72 hours after ICU admission (r value was 0.547, 0.577, 0.754, and 0.783, respectively, all P < 0.01). The MP and LUS at 0 hour of ICU admission were significantly positively correlated with SOFA and PaO2/FiO2 (r value was 0.421, 0.450, and 0.409, 0.536, respectively, all P < 0.01), but no correlation with Lac and APACHEⅡ was found. The ROC curve analysis showed that the MP and LUS at 0 hour and 72 hours had predictive value for the 28-day mortality [the area under the ROC curve (AUC) of MP was 0.836, 0.867; and the AUC of LUS was 0.820, 0.891, all P < 0.01]. Conclusions There was a significant correlation between MP and LUS in patients with moderate to severe ARDS. The MP and LUS could be used early to evaluate the 28-day prognosis of patients with moderate to severe ARDS.

Determinación del poder mecánico en pacientes en ventilación mecánica invasiva en modalidad espontánea / Determination of the mechanical power in patients in invasive mechanical ventilation in spontaneous mode / Determinação da potência mecânica em pacientes com ventilação mecânica invasiva no modo espontâneo

Resumen: Objetivo: Determinar cuál es el poder mecánico (mediante un modelo matemático que puede englobar las posibles causas de lesión pulmonar) otorgado por el ventilador en pacientes bajo ventilación mecánica invasiva en modalidad espontánea VAP (ventilación asisto-proporcional). Material y métodos: Se calculó el poder mecánico y de distensión con las fórmulas: p o d e r m e c a n i c o r s = F R . ∆ V 2 . 1 2 . E L r s + F R . 1 + I : E 60 . I : E . R a w + ∆ V . P E E P 2. Poder mecánico rs = (0.098) · (FR . ΔV) · (Ppico − ½ · ΔP) 3. PD = (0.098) · (PPL − PEEP) · Vt · FR Se realizó en 60 pacientes, la mitad de ellos con ventilación mecánica invasiva en modalidad espontánea VAP, estimando la presión meseta (P pl ) mediante el volumen corriente (Vt), la distensibilidad (C rs ) y la presión positiva al final de la espiración total (PEEPt) dadas por el ventilador mecánico. Resultados: Se incluyeron datos de 60 pacientes bajo ventilación mecánica invasiva, 30 de ellos en la modalidad espontánea: ventilación asisto-proporcional (VAP), de los cuales 100% tuvo retiro de la ventilación exitoso; 30 pacientes como controles emparejados en modalidades controladas, con edad de 65 (DE ± 15) años, 63% hombres y parámetros generales: frecuencia respiratoria (FR) media de 18 (DE ± 5.5) min-1, Vt medio de 0.46 (DE ± 0.1) Lts, Crs media de 55 (DE ± 22) mL/cm H2O, PEEPt de 7.6 (DE ± 3.3) cm H2O, presión pico (P pico ) 20.4 (DE ± 6.9) cm H2O, Ppl de 17.05 (DE ± 5.8) cm H2O. Al calcular el poder mecánico, todas las comparaciones fueron menores en pacientes en modalidad espontánea versus aquellos ventilados con modalidad controlada; se determinaron los siguientes valores: 6.98 (DE ± 1.69) versus 18.49 (DE ± 8.20) J/min (p < 0.001), 7.17 (DE ± 1.67) versus 20.92 (DE ± 9.05) J/min (p < 0.001) y de 4.6 (DE ± 1.64) versus 12.33 (DE ± 7.04) J/min (p < 0.001), en las fórmulas 1, 2 y 3 respectivamente, con un valor promedio para los pacientes en modalidad espontánea de 6.25 (DE ± 1.66) J/min. Conclusiones: La posibilidad de determinar un valor promedio del poder mecánico en pacientes bajo ventilación mecánica invasiva en modalidad VAP puede permitir obtener un parámetro como objetivo a seguir bajo el contexto de su equivalencia estimada en condiciones fisiológicas y, sobre todo, en pacientes en quienes se desean conservar medidas de protección pulmonar y progresar para retirar la ventilación invasiva.

Abstract: Objective: To define which would be the mechanical power (using a mathematical model that can apply to possible causes for lung injury) used by a ventilator, in patients undergoing invasive mechanical ventilation in spontaneous PAV (proportional assist ventilation). Material and methods: The mechanical and distention powers are calculated using the equations: p o d e r m e c a n i c o r s = F R . ∆ V 2 . 1 2 . E L r s + F R . 1 + I : E 60 . I : E . R a w + ∆ V . P E E P 2. Mechanical power rs = (0.098) . (FR . ΔV) . (Ppeak − ½ . ΔP) 3. PD = (0.098) . (PPL − PEEP) . Vt . RF Sixty patients were selected, half of them with invasive mechanical ventilation PAV in spontaneous mode, estimating the plateau pressure (P pl ) though tidal volume value (Vt), distensibility (C rs ), and the positive pressure at the end of a normal exhalation (PEEPt) given by the mechanical ventilator. Results: Data from 60 patients undergoing invasive mechanical ventilation was included, 30 of them through spontaneous modality: proportional assist ventilation (PAV), from which 100% had a successful ventilator tube removal; 30 patients were paired as controls with controlled modalities, with age 65 years (SD ± 15), 63% were men, with the general parameters: mean respiratory frequency (RF) of 18 (SD ± 5.5) min-1, mean Vt of 0.46 (SD ± 0.1) Lts, mean C rs of 55 (SD ± 22) mL/cm H2O, PEEPt of 7.6 (SD ± 3.3) cm H2O, peak pressure (Ppico) 20.4 (SD ± 6.9) cm H2O, Ppl of 17.05 (SD ± 5.8) cm H2O. When comparing the mechanical power, all the results were inferior in patients with spontaneous modality versus patients undergoing controlled modality ventilation, determining the following values: 6.98 (SD ± 1.69) versus 18.49 (SD ± 8.20) J/min (p < 0.001), 7.17 (SD ± 1.67) versus 20.92 (SD ± 9.05) J/min (p < 0.001) and of 4.6 (SD ± 1.64) versus 12.33 (SD ± 7.04) J/min (p < 0.001), in the equations 1, 2, and 3 respectively, with an average value for the patients undergoing spontaneous modality of 6.25 (SD ± 1.66) J/min. Conclusions: The probability of determining a mean value for the mechanical power used in patients undergoing invasive mechanical ventilation on a PAV mode may allow to obtain a standard parameter to follow under the context of its estimated equivalence in physiological conditions, mainly for patients in whom lung protective measures are desired in order to obtain a positive progress and the eventual removal of the invasive ventilation.

Resumo: Objectivo: Determinar qual seria a potência mecânica (usando um modelo matemático que pode englobar às possíveis causas de lesão pulmonar) outorgada pelo ventilador, em pacientes submetidos a ventilação mecânica invasiva no modo espontâneo PAV (Ventilação assistida proporcional). Métodos: Calculamos a potência mecânica e de distensão com as fórmulas: p o d e r m e c a n i c o r s = F R . ∆ V 2 . 1 2 . E L r s + F R . 1 + I : E 60 . I : E . R a w + ∆ V . P E E P 2. Poder mecánico rs = (0.098) · (FR · ΔV) · (Ppico − ½ · ΔP) 3. PD = (0.098) · (PPL − PEEP) · Vt · FR Foram selecionados 60 pacientes, metade com ventilação mecânica invasiva PAV, estimando a pressão de platô (Ppl) mediante o volume corrente (Vt), distensibilidade (Crs), e a pressão positiva ao final de uma expiração total (PEEPt) dadas pelo ventilador mecânico. Resultados: Foram incluídos dados de 60 pacientes com ventilação mecânica invasiva, 30 no modo espontâneo: ventilação assistida proporcional a (PAV), dos quais 100% tinham remoção bem sucedida de ventilação, 30 pacientes com controles em modalidades controladas, com idade de 65 (SD ± 15) anos, 63% homens e parâmetros gerais: frequência respiratória (FR) média de 18 (SD ± 5.5) min-1, Vt médio 0.46 (SD ± 0.1) Lts, Crs média de 55 (SD ± 22) mL/cm H2O, PEEPt de 7.6 cm (SD ± 3.3) com H2O, pressão de pico (Ppico) 20.4 (SD ± 6.9) cm H2O, Ppl de 17.05 (SD ± 5.8) cm H2O. Todas as comparações ao calcular a potência mecânica, foram menores em pacientes no modo espontâneo vs os pacientes ventilados com modo controlado, determinando os seguintes valores: 6.98 (SD ± 1.69) vs 18.49 (SD ± 8.20) J/min (p < 0.001), 7.17 (SD ± 1.67) vs 20.92 (SD ± 9.05) J/min (p < 0.001) e 4.6 (SD ± 1.64) vs 12.33 (SD ± 7.04) J/min (p < 0.001), nas fórmulas 1, 2 e 3, respectivamente, com um valor médio para os pacientes em modo espontâneo de 6.25 (SD ± 1.66) J/min. Conclusões: A possibilidade de determinar um valor médio da potência mecânica em pacientes sob ventilação mecânica invasiva no modo PAV, permitiu obter um parâmetro como objetivo a seguir; no contexto da sua equivalência estimada em condições fisiológicas e acima de tudo, os pacientes que desejamos preservar medidas de proteção pulmonar e progressar para remover a ventilação invasiva.

Asociación y valor predictivo del poder mecánico con los días libres de ventilación mecánica / Association and predictive value of mechanical power with ventilator-free days / Associação e valor preditivo do poder mecânico com os dias livres de ventilação mecânica

Resumen Introducción: La afección pulmonar atribuible a la ventilación mecánica (VM) ha sido denominada lesión pulmonar asociada con la ventilación mecánica (LPAVM). La fórmula del poder mecánico (PM) reúne las principales variables que determinan el desarrollo de la LPAVM. Analizamos la correlación entre el PM y los días libres de ventilación mecánica (DLVMI), así como la capacidad de predicción para DLVMI. Material y métodos: Se estudiaron 40 pacientes ingresados a la unidad de terapia intensiva (UTI) y que cumplieron con los criterios de inclusión. Se recabaron las variables demográficas, clínicas y de laboratorio. Se realizó el cálculo del poder mecánico en las primeras 24 horas de estancia en la UTI y se determinaron los DLVMI, estancia en la UTI y mortalidad en la UTI. Se realizó la prueba de rho de Spearman para determinar la correlación entre PM y DLVM; análisis multivariado de regresión binaria. Para evaluar la capacidad predictiva de las variables que se relacionaron de forma independiente, se compararon las áreas bajo la curva en la curva de características operativas del receptor (ROC). Resultados: PM y DLVM tienen correlación inversa de magnitud intermedia. Se asociaron de manera independiente: PM OR 2.07, IC 95% (1.10-4.09), p = 0.01, frecuencia respiratoria OR 1.5, IC 95% (1.05-2.3), p = 0.04 y Vt/kg (≤ 8.2 mL) un OR 0.01, IC 95% (0.001-0.10), p = 0.002. El área bajo la curva (ABC) fue PM (ABC) 0.75, IC 95% (0.59-0.90), p = 0.007, FR (ABC) 0.71, IC 95% (0.54-0.88), p = 0.01 y Vt/kg (ABC) 0.92, IC (0.83-1.0), p = 0.001. Conclusión: El poder mecánico se correlaciona de forma inversa con los días libres de ventilación mecánica, con adecuada capacidad predictiva para días libres de ventilación mecánica invasiva, con un punto de corte en 13 Joules/min.

Abstract Introduction: Pulmonary disease attributable to mechanical ventilation (MV) has been named ventilator-associated lung injury (VALI). The mechanical power formula (MP) brings together the main variables that determine VALI development. It analyzes the correlation between MP and ventilator-free days (VFD), as well as the predictive capacity for VFD. Material and methods: We studied 40 patients admitted to the intensive care unit (ICU) and who met the inclusion criteria. Demographic, clinical and laboratory data were collected. MP calculation was performed in the first 24 hours of ICU stay and we determined VFD, ICU stay and ICU mortality. The Spearman's rho test was performed to determine the correlation between MP and VFD; we performed the bi-varied and later multivariate binary regression analysis. To evaluate the predictive capacity of the variables that were independently related, we compared the areas under the curve (AUC) in the receiver operating characteristics (COR) curve. Results MP and VFD have an inverse correlation with intermediate magnitude. They were independently associated: MP OR 2.07, 95% CI (1.10-4.09), p = 0.01, respiratory rate OR 1.5, 95% CI (1.05-2.3), p = 0.04 and Tv/ kg (≤ 8.2 mL) OR 0.01, 95% CI (0.001-0.10), p = 0.002. MP (AUC) 0.75, 95% CI (0.59-0.90), p = 0.007, respiratory rate (ABC) 0.71, 95% CI (0.54-0.88), p = 0.01 and Tv/kg (ABC) 0.92, IC (0.83-1.0), p = 0.001. Conclusion: MP and VFD have inverse correlation, with ability for predicting VFD, with a cutoff point of 13 Joules/min.

Resumo Introdução A alteração pulmonar induzida pela ventilação mecânica (VM) definiu-se como lesão pulmonar associada à ventilação (LPAV). A fórmula do poder mecânico (PM) reúne as principais variáveis que determinam o desenvolvimento da LPAV. Analisamos à correlação entre PM e os dias livres de ventilação mecânica (DLVM), assim como a capacidade de previsão para DLVM. Métodos Estudamos 40 pacientes internados na unidade de terapia intensiva (UTI) e que completaram os critérios de inclusão. Foram coletados dados demográficos, clínicos e laboratoriais. O cálculo do PM foi realizado nas primeiras 24 horas da internação na UTI e determinamos DLVM, permanência e mortalidade na UTI. O teste de rho Spearman foi realizado para determinar a correlação entre PM e DLVM; análise multivariada de regressão binária. Para avaliar a capacidade preditiva das variáveis que se relacionaram de maneira independente, comparamos as áreas sob a curva na curva de características operativas do receptor (COR). Resultados PM e DLVM têm correlação inversa de magnitude intermediária. Se associaram de maneira independente: PM OR 2.07, IC 95% (1.10-4.09), p = 0.01, frequência respiratória OR 1.5, IC 95% (1.05-2.3), p = 0.04 e Vt/kg (< 8.2 mL) um OR 0.01, IC 95% (0.001-0.10), p = 0.002. Na área sob a curva (ABC) foi PM (ABC) 0.75, IC 95% (0.59-0.90), p = 0.007, FR (ABC) 0.71, IC 95% (0.54-0.88), p = 0.01 e Vt/kg (ABC) 0.92, IC (0.83-1.0), p = 0.001. Conclusões O poder mecânico têm correlação inversa com os dias livres de ventilação mecânica, com adequada capacidade preditiva para os dias livres de ventilação mecânica invasiva, com um ponto de corte de 13 Joules/min.

Comparação entre dois métodos para determinação de potência mecânica em saltos verticais / Comparison between two methods for determination of mechanical power in vertical jumping

O objetivo do estudo foi comparar valores de potência mecânica de saltos verticais obtidos através do teste de BOSCO (potência teórica, PT) com valores de potência mecânica registrados por uma plataforma de força (potência experimental, PE) e verificar a concordância entre os dois métodos. Onze corredores recreacionais realizaram saltos contínuos máximos durante 60 segundos. Foram utilizados a plataforma de força 3D e o sistema de cinemetria 2D para cálculo da PT e PE, respectivamente. A partir da análise cinemática (Dvideow 5.0) foram obtidos o tempo de voo e o número de saltos. Utilizou-se o teste de Bland e Altman para a análise de concordância entre os métodos. Os valores médios de PT e PE foram de 15,6±2,4 W.kg-1 e 20,8±3,2 W.kg-1, respectivamente, situando-se entre os limites de concordância de ± 2dp. Concluiu-se que a equação de PT é um método conveniente para determinação da potência mecânica durante saltos verticais contínuos.

The aim of this study was to compare the mechanical power values of vertical jumps measured by BOSCO test (Theoretical Power, PT) with mechanical power values registered by force plate (Experimenal Power, PE) and verify the agreement between the two methods. Eleven recreational runners performed continuous maximal jumps for 60 seconds. Force platform 3D and 2D kinematics system were used for calculation of PT and PE, respectively. Data about flight time and number of hops were obtained from the kinematic analysis (Dvideow 5.0). We used Bland & Altman for agreement between the methods. The average values of PT and PE were 15.6 ±2.4 W.kg-1 and 20.8 ±3.2 W.kg-1, respectively, ranging from the agreement limits ±2 s.d. Therefore, the equation of the PT is a convenient method for determining the mechanical power during continuous vertical jumps.

Parâmetros mecânicos e metabólicos do desempenho em intensidade supra-máxima de nado crawl / Mechanical and metabolic parameters of front crawl swim performance at supramaximal intensity

O objetivo deste estudo foi analisar o desempenho supra-máximo no nado crawl (vmax) pelas relações entre energia anaeróbia (Eanaer), potência muscular (Po) e propulsiva (Pu), eficiência mecânica (emec) e propulsiva (ep), economia e força de arrasto (Fr). Onze competidores submeteram-se à avaliação de Fr pelo método de Perturbação da Velocidade e à estimativa da ep, pelas relações entre Fr e a ação do hidrofólio. Eanaer foi quantificada pelo equivalente energético do lactato e da fosfocreatina. Correlações de vmax com Eanaer (0,71), economia (0,65), Fr (0,68), Pu (0,79) e Po (0,69) sugerem que força, potência e disponibilidade de energia sustentam o desempenho em vmax. Contudo, ao restringir Eanaer em vmax, apenas a economia acomoda-se a esta condição (-0,95), enquanto que emec torna-se determinante para Fr (0,97), Pu (0,90) e Po (0,98). Conclui-se que a taxa de trabalho é decisiva no desempenho supramáximo, e que Eanaer subsidia sua produção, mas quando restrita, emec e economia interagem-se como fatores fundamentais para manter a taxa de trabalho no patamar demandado por esta condição de nado.

The purpose of this study was to analyze crawl performance at supramaximal intensity (vmax) from relationships between anaerobic energy (Eanaer), mechanical and propulsive power (Po, Pu), mechanical and propulsive efficiency (emec, ep), and drag force (Fr). Eleven experience swimmers were undergone to the measurement of Fr from the method of Velocity Perturbation, and to estimative the ep from Fr relationships to hydrofoil action. Eanaer was estimated from lactate and phosphocreatine energy equivalents. Correlations of vmax to Eanaer (0,72), economy (0,65), Fr (0,68), Pu (0,79), and Po (0,69) suggest a trend to force, power and energy release to determine performance at vmax. Once Eanaer became constrained, only economy was able to accommodated to these context (-0,95), whereas emec improve their influence on Fr (0,97), Pu (0,90), and Po (0,98). In conclusion, work rate is the main parameter to ensure supramaximal performance, and Eanaer is the major factor in power availability, but when it is constrained, emec and economy interactions plays a fundamental role to maintain the level of work rate production enough to reach supramaximal swim requirements.