Rethinking double triggering: A phenotype rather than a patient–ventilator dyssynchrony?

Adrian Gallardo

Abstract

Double triggering has traditionally been defined as the presence of two consecutive ventilator cycles separated by an expiratory time equal or shorter than 50% of the inspiratory time. It is considered the consequence of a single inspiratory effort and is recognized as one of the most frequent forms of patient–ventilator dyssynchrony. Epidemiological studies report that this entity occurs in approximately 15–25% of mechanically ventilated patients and is associated with longer duration of mechanical ventilation and ICU stay, although a consistent association with mortality has not been demonstrated. However, growing physiological evidence suggests that double triggering does not constitute a homogeneous entity, but rather a phenotypic expression arising from distinct underlying processes.

This reappraisal revisits the conventional conceptual framework of double triggering and proposes a mechanistic reinterpretation. While in rare cases it may represent truly consecutive neural inspiratory efforts, most episodes appear to result from mismatches between respiratory drive and ventilator timing or flow delivery. Premature cycling, insufficient inspiratory flow or reverse triggering may converge into the same observable pattern of two closely spaced ventilator cycles. Despite similar waveform geography, these pathophysiological mechanisms differ substantially and have a potential impact on tidal volume, transpulmonary pressure, and lung stress.

Reconceptualizing double triggering as a phenotype rather than a discrete dyssynchrony entity carries relevant clinical implications. When this pattern is identified, management should focus on elucidating the underlying mechanism through careful waveform inspection and detailed physiologic assessment. Such a mechanism-oriented, pathophysiology-driven approach may optimize ventilator adjustment and allow a more nuanced interpretation of outcome associations attributed to double triggering.

Keywords: Double triggering, Dyssynchronies, Patient-ventilator interactions

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