Frequency and Risk Factors for Reverse Triggering in Pediatric Acute Respiratory Distress Syndrome during Synchronized Intermittent Mandatory Ventilation

Abstract

Rationale: Reverse triggering (RT) occurs when respiratory effort begins after a mandatory breath is initiated by the ventilator. RT may exacerbate ventilator-induced lung injury and lead to breath stacking.Objectives: We sought to describe the frequency and risk factors for RT among patients with acute respiratory distress syndrome (ARDS) and identify risk factors for breath stacking.Methods: We performed a secondary analysis of physiologic data from children on synchronized intermittent mandatory pressure-controlled ventilation enrolled in a single-center randomized controlled trial for ARDS. When children had a spontaneous effort on esophageal manometry, waveforms were recorded and independently analyzed by two investigators to identify RT.Results: We included 81,990 breaths from 100 patient-days and 36 patients. Overall, 2.46% of breaths were RTs, occurring in 15/36 patients (41.6%). A higher tidal volume and a minimal difference between neural respiratory rate and set ventilator rate were independently associated with RT (P = 0.001) in multivariable modeling. Breath stacking occurred in 534 (26.5%) of 2,017 RT breaths and in 14 (93.3%) of 15 patients with RT. In multivariable modeling, breath stacking was more likely to occur when total airway Δpressure (peak inspiratory pressure - positive end-expiratory pressure [PEEP]) at the time patient effort began, peak inspiratory pressure, PEEP, and Δpressure were lower and when patient effort started well after the ventilator-initiated breath (higher phase angle) (all P < 0.05). Together, these parameters were highly predictive of breath stacking (area under the curve, 0.979).Conclusions: Patients with higher tidal volume who have a set ventilator rate close to their spontaneous respiratory rate are more likely to have RT, which results in breath stacking >25% of the time.Clinical trial registered with ClinicalTrials.gov (NCT03266016).

Keywords: acute respiratory distress syndrome; patient–ventilator asynchrony; respiratory entrainment; reverse triggering.

Figures

Figure 1.

The waveform of non–breath stacking (left) and breath stacking (right). Black arrows show airway pressure and flow at initiating spontaneous efforts. The breath on the left has reverse triggering (RT) without a breath stack but still generated a tidal volume of approximately 10 ml/kg (predicted body weight, 15 kg). The breath on the right has RT with a breath stack and resulted in a tidal volume of 16.8 ml/predicted body weight (right). Δesophageal pressure (Pes) shows the amount of change between peak and minimum Pes.

Figure 2.

Phase angle = phase difference/ventilator cycle duration × 360°. This is the standard way of expressing the relationship between machine and neural respiratory activity onset.

Figure 3.

The patterns of reverse triggering (RT) include irregular RT (no clear entrainment pattern), regular RT (clear entrainment pattern of 1:1). (A) Clear entrainment pattern of 1:1. (B) Irregular reverse triggering (no clear entrainment pattern). Red shadings show reverse triggers.

Figure 4.

The boxplots of each variable. (A) The reverse triggering index (RTI) was higher with RRneural getting closer to set RRvent. (B–D) The relationship between RTI and observed respiratory rate (B), tidal volume (Vt)/predicted body weight (pbw) of spontaneous synchronous breath (C) and Vt/pbw of spontaneous asynchronous breath (D). Sixty-five files of RTI = 0, 29 files of 0 < RTI < 20, and six files of RTI > 20. rpm = revolution per minute; RRneural = neural respiratory rate; RRvent = ventilator rate.

Figure 5.

The trend of reverse triggering index and day. The x-axis is the day when spontaneous breathing appeared, which was defined as minute volume of triggered breath/total minute volume >10%.