Reverse triggering is a delayed asynchronous contraction of the diaphragm triggered by passive insufflation by the ventilator in sedated mechanically ventilated patients. The incidence of reverse triggering is unknown. This study aimed at determining the incidence of reverse triggering in critically ill patients under controlled ventilation.
In this ancillary study, patients were continuously monitored with a catheter measuring the electrical activity of the diaphragm. A method for automatic detection of reverse triggering using electrical activity of the diaphragm was developed in a derivation sample and validated in a subsequent sample. The authors assessed the predictive value of the software. In 39 recently intubated patients under assist-control ventilation, a 1-h recording obtained 24 h after intubation was used to determine the primary outcome of the study. The authors also compared patients’ demographics, sedation depth, ventilation settings, and time to transition to assisted ventilation or extubation according to the median rate of reverse triggering.
The positive and negative predictive value of the software for detecting reverse triggering were 0.74 (95% CI, 0.67 to 0.81) and 0.97 (95% CI, 0.96 to 0.98). Using a threshold of 1 μV of electrical activity to define diaphragm activation, median reverse triggering rate was 8% (range, 0.1 to 75), with 44% (17 of 39) of patients having greater than or equal to 10% of breaths with reverse triggering. Using a threshold of 3 μV, 26% (10 of 39) of patients had greater than or equal to 10% reverse triggering. Patients with more reverse triggering were more likely to progress to an assisted mode or extubation within the following 24 h (12 of 39 [68%]) vs. 7 of 20 [35%]; P = 0.039).
Reverse triggering detection based on electrical activity of the diaphragm suggests that this asynchrony is highly prevalent at 24 h after intubation under assist-control ventilation. Reverse triggering seems to occur during the transition phase between deep sedation and the onset of patient triggering.
In patients undergoing invasive mechanical ventilation, dyssynchrony between the patients’ respiratory efforts and the programed ventilatory mode may have immediate adverse effects on oxygenation and ventilation, as well as potentially increasing lung injury.
A variety of dyssynchrony subtypes have been previously categorized. Reverse dyssynchrony is characterized by the patients’ inspiratory efforts occurring after ventilator-triggered breaths. It has only recently been reported in small observational studies, and its characteristics have been not well delineated.
Using standardized placement of a catheter to continuously monitor electrical activity of the diaphragm in patients within 12 h of intubation along with recording of airway pressure and flow, the authors determined the incidence of reverse triggering (defined as electrical activity starting after initiation of a mechanical breath reaching more than 1 μV) in patients on either a volume or pressure assist–control ventilator mode using customized automated software. Differences in demographics, sedative depth, and ventilator management between patients with and without reverse triggering were also assessed.
The performance of the software was assessed by three trained observers in the first 10 patients and validated in five additional patients.
The automated software had positive and negative predictive values of 0.74 (95% CI, 0.67 to 0.81) and 0.97 (95% CI, 0.96 to 0.98), respectively.
In 39 patients primarily intubated for medical reasons and studied for 1 h at 24 h after intubation, the median reverse triggering rate was 8% (95% CI, 0.1 to 75); 44% of patients had reverse triggering in greater than or equal to 10% of breaths. The wide variability in frequency was not explained by patient demographics, reason for intubation, disease severity, or depth or type of sedation.
The authors suggest that reverse triggering is common at 24 h after intubation and occurs during the transition between deep sedation and onset of patient triggering, leading to extubation.