An optimized set-up for helmet noninvasive ventilation improves pressure support delivery and patient-ventilator interaction

Objective: To test the effects on mechanical performance of helmet noninvasive ventilation (NIV) of an optimized set-up concerning the ventilator settings, the ventilator circuit and the helmet itself. Subjects and methods: In a bench study, helmet NIV was applied to a physical model. Pressurization and depressurization rates and minute ventilation (MV) were measured under 24 conditions including pressure support of 10 or 20 cmH₂O, positive end expiratory pressure (PEEP) of 5 or 10 cmH₂O, ventilator circuit with "high", "intermediate" or "low" resistance, and cushion deflated or inflated. In a clinical study pressurization and depressurization rates, MV and patient-ventilator interactions were compared in six patients with acute respiratory failure during conventional versus an "optimized" set-up (PEEP increased to 10 cmH₂O, low resistance circuit and cushion inflated). Results: In the bench study, all adjustments simultaneously applied (increased PEEP, inflated cushion and low resistance circuit) increased pressurization rate (46.7 ± 2.8 vs. 28.3 ± 0.6 %, p <0.05), depressurization rate (82.9 ± 1.9 vs. 59.8 ± 1.1 %, p ≤ 0.05) and patient MV (8.5 ± 3.2 vs. 7.4 ± 2.8 l/min, p <0.05), and decreased leaks (17.4 ± 6.0 vs. 33.6 ± 6.0 %, p <0.05) compared to the basal set-up. In the clinical study, the optimized set-up increased pressurization rate (51.0 ± 3.5 vs. 30.8 ± 6.9 %, p <0.002), depressurization rate (48.2 ± 3.3 vs. 34.2 ± 4.6 %, p <0.0001) and total MV (27.7 ± 7.0 vs. 24.6 ± 6.9 l/min, p <0.02), and decreased ineffective efforts (3.5 ± 5.4 vs. 20.3 ± 12.4 %, p <0.0001) and inspiratory delay (243 ± 109 vs. 461 ± 181 ms, p <0.005). Conclusions: An optimized set-up for helmet NIV that limits device compliance and ventilator circuit resistance as much as possible is highly effective in improving pressure support delivery and patient-ventilator interaction.