Abstract
OBJECTIVE: To compare helmet noninvasive ventilation (NIV), in terms of patient-ventilator interaction and performance, using 2 different circuits for connection: a double tube circuit (with one inspiratory and one expiratory line) and a standard circuit (a Y-piece connected only to one side of the helmet, closing the other side).
METHODS: A manikin, connected to a test lung set at 2 breathing frequencies (20 and 30 breaths/min), was ventilated in pressure support ventilation (PSV) mode with 2 different settings, randomly applied, of the ratio of pressurization time to expiratory trigger time (Tpress/Texp-trigger) 50%/25%, default setting, and Tpress/Texp-trigger 80%/60%, fast setting, through a helmet. The helmet was connected to the ventilator randomly with the double and the standard circuit. We measured inspiratory trigger delay (Tinsp-delay), expiratory trigger delay (Texp-delay), Tpress), time of synchrony (Tsynch), trigger pressure drop, inspiratory pressure-time product (PTP), PTP at 300 ms and 500 ms, and PTP at 500 ms expressed as percentage of an ideal PTP500 (PTP500 index).
RESULTS: At both breathing frequencies and ventilator settings, helmet NIV with the double tube circuit showed better patient-ventilator interaction, with shorter Tinsp-delay, Texp-delay, and Tpress; longer Tsynch; and higher PTP300, PTP500, and PTP500 index (all P < .01).
CONCLUSIONS: The double tube circuit had significantly better patient-ventilator interaction and a lower rate of wasted effort at 30 breaths/min.
Footnotes
- Correspondence: Giuliano Ferrone MD, Department of Intensive Care and Anesthesia, Policlinico A Gemelli, Catholic University of Rome, Largo Francesco Vito 1, 00168, Rome, Italy. E-mail: giulianoferrone{at}yahoo.it.
The authors have disclosed no conflicts of interest.
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