Susceptibility for Entrainment: Role of Ventilator Settings on the Occurrence of Reverse Triggering and Its Physiological Consequences - the SEVeRe Study

Summary

Background: Reverse triggering (RT) is a frequent phenomenon observed in sedated patients under a mechanical ventilation mode called assist-control ventilation. RT is when the ventilator would trigger the patient's respiratory effort instead of the correct order of the patient's respiratory effort triggering the ventilator. Reverse triggering can have negative consequences (loss of protective lung ventilation, and causing double breaths - with the ventilator giving two consecutive breaths and not allowing the patient to exhale) but also offer some protective effects (avoid diaphragm disuse atrophy). The balance of its negative vs positive effects depends on its frequency and magnitude of its associated respiratory effort. Respiratory entrainment is the most often referred mechanism involving a change in patient's rate of breathing effort from that of patient's intrinsic rate to the rate of mechanical insufflation. The specific ventilatory settings associated with or responsible for RT remains unknown.

Aims: To assess in mechanically ventilated critically ill patients the influence of the set respiratory rate (RR) and tidal volume (Vt) on the presence/development of RT and to describe the pattern of respiratory muscle activity during Reverse Triggering (RT).

Methods. 30 adult patients (15 in each group), sedated and under assist-controlled ventilation will be included. Ventilator settings will be modified to modulate the frequency and magnitude of reverse triggering. Initially, with the ventilator on a mode called volume control, which means the ventilator controls the amount of air (tidal volume) and the number of breaths the patients gets every minute (respiratory rate \[RR\]). The tidal volume will be set at the current standard clinical practice setting (6 ml/kg of predicted body weight). The presence of an intrinsic respiratory rate will be assessed with an end-expiratory occlusion maneuver. Next, the number of breaths the ventilator gives per minute (RR) will be changed from 6 breaths less to 6 breaths more, in steps of 2 breaths every minute. The protocol will be repeated again changing the amount of air the patients gets (tidal volume) from 4, 5, 7 and 8 ml/kg. Continuous recordings of airway pressure, flow, esophageal pressure, electrical activity of the diaphragm, main accessory muscles and frontal electroencephalography will be obtained during the protocol and baseline clinical and physiological characteristics and outcomes will be recorded. A validated software will be used to detect RT and measure the intensity and timing of each muscle electrical activity and the magnitude of the inspiratory effort during RT.

Conditions

• Respiration, Artificial
• Reverse Triggering

Interventions

OTHER

Changes in the ventilator respiratory rate and tidal volume

With the ventilator on volume control and Vt at 6 ml/kg of predicted body weight (PBW) (standard clinical practice), an end-expiratory occlusion of 30 seconds on the ventilator will be performed to search for intrinsic respiratory rate (RR). The set RR will be modified from 6 breaths per minute (bpm) below up to 6 bpm above the clinical RR in steps of 2 bpm every 1 minute (random order). The changes in RR described above will be repeated with Vt set at 5, 7 and 8 ml/kg PBW (random order). The steps described above will be aborted at any point if SpO2 drops below 85% for at least two minutes, mean arterial pressure drops below 60 mmHg, or plateau pressure \>35 cmH2O. If an intrinsic respiratory rate ≥8 bpm is present and P/F ratio is ≥150, it will be propose to the clinician to place the patient in pressure support at a level preferred by clinicians for 5 minutes. If the patient tolerates well, it will be propose to the clinician to maintain the patient in pressure support ventilation,

Sponsors & Collaborators

• Unity Health Toronto

  lead OTHER

Principal Investigators

• Laurent Brochard · Unity Health Toronto - St. Michael's Hospital

Study Design

Allocation

NA

Purpose

OTHER

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2025-01-30

Primary Completion

2026-03-01

Completion

2026-03-01

Countries

• Canada

Study Locations