Subject–ventilator synchrony during neural versus pneumatically triggered non-invasive helmet ventilation

ObjectivePatient–ventilator synchrony during non-invasive pressure support ventilation with the helmet device is often compromised when conventional pneumatic triggering and cycling-off were used. A possible solution to this shortcoming is to replace the pneumatic triggering with neural triggering and cycling-off—using the diaphragm electrical activity (EAdi). This signal is insensitive to leaks and to the compliance of the ventilator circuit.DesignRandomized, single-blinded, experimental study.SettingUniversity Hospital.Participants and subjectsSeven healthy human volunteers.InterventionsPneumatic triggering and cycling-off were compared to neural triggering and cycling-off during NIV delivered with the helmet.Measurements and resultsTriggering and cycling-off delays, wasted efforts, and breathing comfort were determined during restricted breathing efforts (<20% of voluntary maximum EAdi) with various combinations of pressure support (PSV) (5, 10, 20 cm H2O) and respiratory rates (10, 20, 30 breath/min). During pneumatic triggering and cycling-off, the subject–ventilator synchrony was progressively more impaired with increasing respiratory rate and levels of PSV (p < 0.001). During neural triggering and cycling-off, effect of increasing respiratory rate and levels of PSV on subject–ventilator synchrony was minimal. Breathing comfort was higher during neural triggering than during pneumatic triggering (p < 0.001).ConclusionsThe present study demonstrates in healthy subjects that subject–ventilator synchrony, trigger effort, and breathing comfort with a helmet interface are considerably less impaired during increasing levels of PSV and respiratory rates with neural triggering and cycling-off, compared to conventional pneumatic triggering and cycling-off.