Pulmonary strain and end-expiratory lung volume during apnea test: a comparative analysis using electrical impedance tomography.

The apnea test, employed for brain death assessment, aims to demonstrate the absence of respiratory drive due to hypercapnia. The tracheal oxygen insufflation apnea test mode (I-AT) involves disconnecting the patient from invasive mechanical ventilation (iMV) for approximately 8 minutes while maintaining oxygenation. This test supports the diagnosis of brain death based on a specified increase in PaCO2. Common complications include hypoxemia and hemodynamic instability, and lung collapse-induced reduction in end-expiratory lung volume (EELV). In our case series utilizing electrical impedance tomography (EIT), we observed that continuous positive airway pressure during the apnea test (CPAP-AT) effectively mitigated lung collapse. This resulted in improved pulmonary strain compared to the disconnection of iMV. These findings suggest the potential benefits of routine CPAP-AT, particularly for potential lung donors, emphasizing the relevance of our study in providing quantitative insights into EELV loss and its association with pulmonary strain and potential lung injury.

La prueba de apnea es una técnica diagnóstica ampliamente utilizada para la evaluación de la muerte cerebral, con el objetivo de demostrar la ausencia de impulso respiratorio debido a la hipercapnia. La variante de la prueba de apnea con insuflación de oxígeno traqueal (I-AT) implica desconectar al paciente de la ventilación mecánica invasiva (iVM) durante aproximadamente 8 minutos, manteniendo la oxigenación mediante un catéter de insuflación. Esta prueba respalda el diagnóstico de muerte cerebral cuando se determina un aumento de la PaCO 2 superior a 20 mmHg en comparación con el valor inicial o un nivel de PaCO 2 superior a 60 mmHg al final de la prueba. En nuestra serie de casos, la implementación de la tomografía de impedancia eléctrica (EIT) reveló que la prueba de apnea con presión positiva continua (CPAPAT) mitiga eficazmente el colapso pulmonar. Este enfoque resulta en una mejora en la tensión pulmonar en comparación con la desconexión de iMV, demostrando su relevancia en el contexto de potenciales donantes de pulmones.

Trigger reverso durante ventilación mecánica: diagnóstico e implicaciones clínicas / Reverse triggering during mechanical ventilation: Diagnosis and clinical implications

Esta revisión aborda el fenómeno «trigger reverso», una asincronía que se presenta en pacientes sedados o en transición de despertar, con una prevalencia en estos grupos del 30% al 90%. Los mecanismos fisiopatológicos aún no están claros, pero se propone el «entrainment» como uno de ellos. Detectar esta asincronía es complejo y se han usado métodos como inspección visual, presión esofágica, ecografía diafragmática y métodos automáticos. El trigger reverso puede tener efectos en la función pulmonar y diafragmática, mediados porbablemente por el nivel de esfuerzo respiratorio y la activación excéntrica del diafragma. El manejo óptimo no está establecido y puede incluir ajuste de parámetros ventilatorios, frecuencia respiratoria, nivel de sedación y en casos extremos, bloqueo neuromuscular. Es importante comprender su significación, su detección e incrementar la investigación para mejorar su manejo clínico y sus potenciales efectos en los pacientes críticamente enfermos. (AU)

This review addresses the phenomenon of “reverse triggering”, an asynchrony that occurs in deeply sedated or patients in transition from deep to light sedation. Reverse triggering has been reported to occur between 30% and 90% of ventilated patients. The pathophysiological mechanisms are still unclear, but “entrainment” is proposed as one of them. Detecting this asynchrony is crucial, and methods such as visual inspection, esophageal pressure, diaphragmatic ultrasound, and automatic methods have been used. Reverse triggering may have effects on lung and diaphragm function, probably mediated by the level of breathing effort and eccentric activation of the diaphragm. The optimal management of reverse triggering is not established and may include adjustment of ventilatory parameters as well as sedation level, and in extreme cases, neuromuscular blockade. It is important to understand the significance of this condition, its detection, but also to conduct dedicated research to improve its clinical management and its potential effects in critically ill patients. (AU)

Reverse triggering during mechanical ventilation: Diagnosis and clinical implications.

This review addresses the phenomenon of "reverse triggering", an asynchrony that occurs in deeply sedated patients or patients in transition from deep to light sedation. Reverse triggering has been reported to occur in 30-90% of all ventilated patients. The underlying pathophysiological mechanisms remain unclear, but "entrainment" is proposed as one of them. Detecting this asynchrony is crucial, and methods such as visual inspection, esophageal pressure, diaphragmatic ultrasound and automated methods have been used. Reverse triggering may have effects on lung and diaphragm function, probably mediated by the level of breathing effort and eccentric activation of the diaphragm. The optimal management of reverse triggering has not been established, but may include the adjustment of ventilatory parameters as well as of sedation level, and in extreme cases, neuromuscular block. It is important to understand the significance of this condition and its detection, but also to conduct dedicated research to improve its clinical management and potential effects in critically ill patients.