title: Performance of different continuous positive airway pressure helmets equipped with safety valves during failure of fresh gas supply.
abstract: OBJECTIVE
  We assessed the performance of different continuous positive airway pressure (CPAP) helmets equipped with a safety valve during discontinuation of fresh gas flow.
  
  
  METHODS
  This was a physiological study of five healthy volunteers. We delivered CPAP (fresh gas flow 60 l/min, FiO(2) 60%, PEEP 5 cmH(2)O) with three different helmets in a random sequence: 4Vent (Rüsch), HelmHAR-cp (Harol) and CaStar CP210 (StarMed). For each helmet we randomly applied, for up to 4 min, three disconnections of fresh gas flow: helmet inlet (D(inlet)), flowmeter (D(flowmeter)) and gas source (D(source)). We continuously recorded from a nostril: end-tidal CO(2) (PetCO(2)), inspiratory CO(2) (PiCO(2)), fraction of inspired oxygen (FiO(2)) and respiratory rate (RR).
  
  
  RESULTS
  During every disconnection we observed an increase in PiCO(2) and PetCO(2) with a drop in FiO(2), while RR did not change. FiO(2) decreased more quickly in the CaStar, equipped with the largest safety valve, during D(source) and D(flowmeter), while FiO(2) decreased more quickly during D(inlet) in CaStar and in 4Vent. PiCO(2) resulted in a lower increase in CaStar during D(source) and D(flowmeter) compared to 4Vent. PetCO(2) in CaStar increases more slowly compared to 4Vent during D(source) and more slowly compared to the other two helmets during D(flowmeter). During D(inlet) similar degrees of CO(2) rebreathing and PetCO(2) were recorded among all the helmets.
  
  
  CONCLUSIONS
  To minimize CO(2) rebreathing during disconnection of the fresh gas supply while performing helmet CPAP, it is desirable to utilize large helmets with a large anti-suffocation valve. Monitoring and alarm systems should be employed for safe application of helmet CPAP.
authors: Department of Perioperative Medicine and Intensive Care, San Gerardo Hospital, Via Pergolesi 33, Monza, MB, Italy.
authors: Manuela
authors: M
authors: Milan
authors: Alberto
authors: A
authors: Zanella
authors: Stefano
authors: S
authors: Isgrò
authors: Salua Abd El Aziz El Sayed
authors: SA
authors: Deab
authors: Federico
authors: F
authors: Magni
authors: Antonio
authors: A
authors: Pesenti
authors: Nicolò
authors: N
authors: Patroniti
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000032:analysis; D045422:Continuous Positive Airway Pressure / Q000295:instrumentation*; D004868:Equipment Failure; D004869:Equipment Safety; D005260:Female; D006801:Humans; D008297:Male; D010100:Oxygen / Q000008:administration & dosage; D012134:Respiratory Protective Devices / Q000592:standards*; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen