Comparative evaluation of three interfaces for non-invasive ventilation: a randomized cross-over design physiologic study on healthy volunteers

Abstract

Introduction: Interface choice is crucial for non-invasive ventilation (NIV) success. We compared a new interface, the helmet next (HN), with the facial mask (FM) and the standard helmet (HS) in twelve healthy volunteers.

Methods: In this study, five NIV trials were randomly applied, preceded and followed by a trial of unassisted spontaneous breathing (SB). Baseline settings, for example, 5 cmH2O of both inspiratory pressure support (PS) and positive end-expiratory pressure (PEEP), were applied through FM, HS and HN, while increased settings (PS and PEEP of 8 cmH2O) were only applied through HS and HN. We measured flow, airway, esophageal and gastric pressures, and calculated inspiratory effort indexes and trigger delays. Comfort was assessed with a visual-analog-scale.

Results: We found that FM, HS and HN at baseline settings were not significantly different with respect to inspiratory effort indexes and comfort. Inspiratory trigger delay and time of synchrony (TI,synchrony) were significantly improved by FM compared to both helmets, whereas expiratory trigger delay was shorter with FM, as opposed to HS only. HN at increased settings performed better than FM in decreasing inspiratory effort measured by pressure-time product of transdiaphragmatic pressure (PTPdi)/breath (10.7 ± 9.9 versus 17.0 ± 11.0 cmH2Os), and PTPdi/min (128 ± 96 versus 204 ± 81 cmH2Os/min), and PTPdi/L (12.6 ± 9.9 versus 30.2 ± 16.8 cmH2Os/L). TI, synchrony was inferior between HN and HS at increased settings and FM.

Conclusions: HN might hold some advantages with respect to interaction and synchrony between subject and ventilator, but studies on patients are needed to confirm these findings.

Trial registration: ClinicalTrials.gov NCT01610960.

Figures

Figure 1

Schematic representation of the experimental design. (A) Spontaneous breathing; (B) face mask; (C) helmet standard; (D) helmet next. Pao, pressure at the airway opening; Pes, esophageal pressure; Pga, gastric pressure.

Figure 2

Helmet next. The new helmet (Helmet next) is composed of a rigid plastic ring (1), inflatable cushion (2) with its inflating line (3), anular opening ring secured to the rigid ring underneath the cushion (4), and transparent hood (5). The helmet is secured to the head by the inflated cushion placed around the neck below the jaw.

Figure 3

Representative traces of a patient (patient 1) during the randomized trials for spontaneous breathing, face mask at PEEP and PS of 5 cmH2O, helmet standard at PEEP and PS of 5 cmH2O, helmet standard at PEEP and PS of 8 cmH2O, helmet next at PEEP and PS of 5 cmH2O, helmet next at PEEP and PS of 8 cmH2O, and spontaneous breathing. Pao, Flow, Pes, Pga, and Pdi are shown from top to bottom. FM, face mask; HN, helmet next; HS, helmet standard; Pao, pressure at the airway opening; Pdi, transdiaphragmatic pressure; PEEP, positive end-expiratory pressure; Pe, esophageal pressure; Pga, gastric pressure; PS, pressure support.

Figure 4

The pressure-time product of the transdiaphragmatic pressure calculated per breath, per minute, and per liter. (A) Calculation per breath; (B) calculation per minute; (C) calculation per liter. FM: face mask; HN: helmet next; HS: helmet standard; PEEP: positive end-expiratory pressure; PS: pressure support; PTPdi: pressure-time product of the transdiaphragmatic pressure; SB: spontaneous breathing.