reverse triggering is when patient initiates 2nd breath

Ventilator graphics including pressure vs time (top), flow vs time (second from top), volume vs time (next to bottom), and electrical activity of the diaphragm vs time (bottom) demonstrated stacked breaths (orange bar) and evidence of patient triggering on the second breath (yellow arrow and white vertical line) but not first breath, consistent with reverse triggering asynchrony.

The ventilator waveforms demonstrate stacked breaths with several examples of 2 distinct paired tidal volumes (Figure 2, orange bar). In each case, the first breath is a time-triggered mandatory (controlled) breath and the second breath is the result of diaphragmatic electrical activity. The white vertical line on Figure 2 depicts the onset of the electrical activity of the diaphragm as demonstrated with the NAVA catheter (Figure 2, bottom tracing)—clearly after the first breath is being delivered—and satisfies criteria for an asynchrony called reverse triggering.

Although NAVA catheters are not commonly used, the clinician can also recognize patient effort by a drop in airway pressure (Figure 2, yellow arrow) for the second but not first of the paired breaths.

Reverse triggering is a form of patient-ventilator interaction in which respiratory muscle contraction occurs after the onset of a passive mandatory breath. It is thought that the passive mechanical thoracic insufflation triggers a patient-initiated breath as a reflex action. In cases such as the one illustrated here, this respiratory muscle activity is strong enough to trigger a second stacked or double cycled breath. This form of breath stacking differs from classical double trigger asynchronies, in which both paired breaths are initiated by the patient (double triggering is when patient initiates both breaths). Reverse triggering was initially observed in deeply sedated patients and has been seen in brain-dead patients. Newer data suggest reverse triggering is more common than originally thought.123456

Footnotes

  1. SEEK Questionnaires ↩

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  3. Mellado Artigas R, Damiani LF, Piraino T, et al. Reverse triggering dyssynchrony 24 h after initiation of mechanical ventilation. Anesthesiology. 2021;134(5):760-769. PubMed ↩

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  5. Mirabella L, Cinnella G, Costa R, et al. Patient-ventilator asynchronies: clinical implications and practical solutions. Respiratory Care. 2020;65(11):1751-1766. ↩

  6. Oto B, Annesi J, Foley RJ. Patient-ventilator dyssynchrony in the intensive care unit: a practical approach to diagnosis and management. Anaesth Intensive Care. 2021;49(2):86-97. PubMed ↩