Classifying different types of double triggering based on airway pressure and flow deflection in mechanically ventilated patients

BACKGROUND: Double-triggering (DT) is a frequent type of patient-ventilator asynchrony and has potentially severe consequences, such as alveolar overdistention or the generation of intrinsic PEEP. However, the first breath of DT could be patient-triggered (DT-P), auto-triggered (DT-A), or ventilator-triggered (DT-V). OBJECTIVE: To differentiate DT-P, DT-A, and DT-V using airway pressure or flow changes during the trigger-delay phase in ventilated patients. METHODS: Fourteen mechanically ventilated patients with DT were included. All patients were on flow-triggered ventilation modes and received either continuous mandatory ventilation or pressure support ventilation. Breaths in which the first breath was associated with an esophageal pressure drop of > 1 cm H₂O were categorized as DT-P. Breaths in which the first breath occurred at the ventilator set cycle were categorized as DT-V. Breaths in which the first breath occurred earlier than the ventilator set cycle without esophageal pressure drop were categorized as DT-A. The pressure drop and flow change at 0.13 s (PD₀₁₃ and F_{0 13}, respectively) in the trigger-delay phase were calculated from the nadir. RESULTS: There were 507 double-triggered breaths: 271 DT-V (53%), 50 DT-A (10%), and 186 DT-P (37%). The PD_{0 13} for DT-V, DT-A, and DT-P were 0.16 ± 0.12 cm H₂O, 0.25 ± 0.17 cm H₂O, and 1.34 ± 0.67 cm H₂O, respectively. The F_{0 13} for DT-V, DT-A, and DT-P were 2.11 ± 2.31 L/min, 2.64 ± 2.07 L/min, and 16.51 ± 8.02 L/min, respectively. The best discriminatory criteria for differentiating DT-P from DT-V and DT-A, based on the Youden index (sensitivity + specificity - 1) was PD_{0 13} ≥: 0.49 cm H₂O, which had a Youden index of 95%. CONCLUSION: DT-P can be distinguished from DT-V and DT-A by using airway pressure deflections in the trigger-delay phase.