Resumption of diaphragmatic activity after intubation often occurs with a pattern consistent with reverse triggering
CCCF ePoster library. Telias I. 11/12/19; 283423; EP91
Dr. Irene Telias
Dr. Irene Telias
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Topic: Retrospective or Prospective Cohort Study or Case Series

Dubo, Sebastián 1-4; Telias, Irene 3,4; Rauseo, Michela3,4; Damiani, Felipe3,4; Mellado-Artigas, Ricard​3,4; Laurent Brochard 3,4 

1Departamento de Kinesiología, Universidad de Concepción, Concepción, Chile; 2PhD Program in Medical Science, Universidad de la Frontera, Temuco, Chile; 3Interdepartmental Division of Critical Care Medicine, University of Toronto, St. Michael's Hospital, Toronto, Canada; 4Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada

Background. Reverse triggering occurs when patients´ respiratory muscle contraction follows and is entrained by controlled mechanical insufflation (i.e. effort is triggered by the ventilator)1. Physiological mechanisms and clinical impact remain unclear. Entrainment of the respiratory rhythm to cyclic lung inflation contributes to the phenomenon1. It was first described in patients that appeared heavily sedated and susceptibility to entrainment is higher with low brain activity and respiratory drive2–5. Therefore, we hypothesized that in intubated patients, the first recognizable pattern of inspiratory effort after intubation may often be consistent with reverse triggering.

Objective. Determine the proportion of critically ill patients in whom resumption of diaphragmatic electrical activity (EAdi) after intubation occurs with a pattern consistent with reverse triggering.

Methods. Ancillary analysis of the DIVIP Study, a prospective observational cohort study (NCT02434016) in which adult patients admitted to the ICU and intubated had a feeding tube containing an array of electrodes to measure EAdi (EAdi monitoring). Data acquisition and analysis: Ventilator trends were acquired from the day of endotracheal intubation until resumption of stable continuous EAdi (presence of a median EAdi peak > 5 µV for 24hr) or 5 days after study enrollment. Additionally, 1 hr-recording of real-time ventilator tracings (Paw, flow, volume, and EAdi) was performed daily, every 24h. The 1hr-recording corresponding to the day of EAdi resumption was analyzed offline. Patients without resumption of EAdi within 5 days were excluded from this analysis. Each tracing (one per patient) was visually classified as 1) Absence of EAdi: machine-trigger breaths defined by a cyclic increase in flow and pressure without an increase in EAdi; or 2) Presence of EAdi: increase in EAdi tracing during the breath cycle. Tracings with EAdi were classified into Spontaneous efforts: all breaths being patient-triggered breath, presence of a negative inflection in Paw or subtle change in flow before insufflation concurrent with an increase of EAdi signal starting prior to insufflation; or Reverse Triggering (RT): breathing efforts in which the increase in EAdi starts after the beginning of machine-trigger breaths (Fig 1). In patients in whom EAdi activity was classified as “Spontaneous effort”, the tracing corresponding to the day prior was analyzed to explore if the first recognizable pattern of EAdi was RT.

Results. From June 2015 to August 2018, 70 patients were included, 10 of which were excluded from this analysis. In the remaining 60, 5 patients were classified as Absence of EAdi and 55 patients as Presence of EAdi. 47 patients (85%) had spontaneous efforts during the day of EAdi resumption and were mainly ventilated in pressure support (34/47, 71%). 8 patients (15%) were classified as having RT activity (Table 1). Median EAdi peak was 6.1 µV (IQR 5.2-15.1). RT was only detected during assist-control modes. When considering only patients under assist-control modes during the day of EAdi resumption the prevalence of RT increased to 47% (8/9). Three additional patients classified as spontaneous efforts exhibited RT the day before of EAdi resumption, all occurring during volume assist-control ventilation.

Conclusion. Reverse Triggering is present in more than half of the patients who resume diaphragmatic activity after intubation in assist-control mode.

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1. Akoumianaki, E. et al. Mechanical ventilation-induced reverse-triggered breaths: A frequently unrecognized form of neuromechanical coupling. Chest143, 927–938 (2013).
2. Burke, P. G. R. et al. State-dependent control of breathing by the retrotrapezoid nucleus. J. Physiol.593, 2909–2926 (2015).
3. Eldridge, F. L., Paydarfar, D., Wagner, P. G. & Dowell, R. T. Phase resetting of respiratory rhythm: effect of changing respiratory ‘drive'. Am. J. Physiol. Integr. Comp. Physiol.257, R271–R277 (1989).
4. Simon, P. M. et al. Entrainment of Respiration in Humans by Periodic Lung Inflations. Am. J. Respir. Crit. Care Med.160, 950–960 (1999).
5. Simon, P. M., Habel, A. M., Daubenspeck, J. A. & Leiter, J. C. Vagal feedback in the entrainment of respiration to mechanical ventilation in sleeping humans. J. Appl. Physiol.89, 760–769 (2000).

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