title: An optimized set-up for helmet noninvasive ventilation improves pressure support delivery and patient-ventilator interaction.
abstract: 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.
  
  
  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 cm H(2)O, positive end expiratory pressure (PEEP) of 5 or 10 cm H(2)O, 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 cm H(2)O, 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.
authors.affiliation: Dipartimento di Emergenza Urgenza, S.C. di Anestesia e Rianimazione I, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy. francesco.mojoli@unipv.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Mojoli
authors.forename: Giorgio A
authors.initials: GA
authors.lastname: Iotti
authors.forename: Ilaria
authors.initials: I
authors.lastname: Currò
authors.forename: Marco
authors.initials: M
authors.lastname: Pozzi
authors.forename: Gabriele
authors.initials: G
authors.lastname: Via
authors.forename: Aaron
authors.initials: A
authors.lastname: Venti
authors.forename: Antonio
authors.initials: A
authors.lastname: Braschi
mesh_terms: D000208:Acute Disease; D004867:Equipment Design; D006801:Humans; D063087:Noninvasive Ventilation / Q000295:instrumentation*; D011175:Positive-Pressure Respiration; D012131:Respiratory Insufficiency / Q000628:therapy; D012122:Ventilators, Mechanical