title: Influence of two different interfaces for noninvasive ventilation compared to invasive ventilation on the mechanical properties and performance of a respiratory system: a lung model study.
abstract: BACKGROUND
  Noninvasive ventilation (NIV) is increasingly used in intensive care medicine, but only little information is available how different NIV interfaces affect the performance of a ventilatory system. Therefore, we compared delay times, pressure time products (PTPs), and wasted efforts during inspiration among patients receiving invasive ventilation and NIV with a helmet (NIV-h) or a face mask (NIV-fm).
  
  
  METHODS
  Using an in vitro lung model capable of simulating spontaneous breathing, gas flow and airway pressure were measured with varying positive end-expiratory pressure and pressure support (PS) levels. Wasted efforts were determined while lung compliance, respiratory rate (RR), continuous positive airway pressure (CPAP), and PS levels were changed.
  
  
  RESULTS
  Delay times were more than twice as long with a helmet compared to NIV-fm or invasive ventilation (p < 0.001), but decreased during NIV-h with increasing CPAP (p < 0.001) and PS levels (p < 0.001). During the initial inspiratory phase, PTP was smaller with NIV-h compared to NIV-fm or invasive ventilation, but not so when a complete inspiration with PS was evaluated. Wasted efforts occurred earlier during NIV-h and were aggravated with rising PS, RR, and compliance.
  
  
  CONCLUSIONS
  Although delay times are prolonged during NIV-h, PTP is initially smaller compared to NIV-fm and invasive ventilation, indicating less work of breathing due to the high volume the patient can access. Increasing the CPAP or PS level decreases delay times in NIV-h and should therefore be considered whenever possible. Wasted inspiratory efforts occurred at higher RRs and should carefully be monitored during NIV.
authors.affiliation: Department of Anaesthesiology, Emergency and Intensive Care Medicine, Georg-August-University of Göttingen, Robert Koch Str. 40, D-37075 Göttingen, Germany. pneuman@gwdg.de
authors.forename: Onnen
authors.initials: O
authors.lastname: Moerer
authors.forename: Sven
authors.initials: S
authors.lastname: Fischer
authors.forename: Michael
authors.initials: M
authors.lastname: Hartelt
authors.forename: Bahar
authors.initials: B
authors.lastname: Kuvaki
authors.forename: Michael
authors.initials: M
authors.lastname: Quintel
authors.forename: Peter
authors.initials: P
authors.lastname: Neumann
mesh_terms: D006260:Head Protective Devices; D006801:Humans; D008170:Lung Compliance / Q000502:physiology; D008397:Masks; D008954:Models, Biological; D011175:Positive-Pressure Respiration / Q000295:instrumentation* / Q000379:methods; D015656:Respiratory Mechanics / Q000502:physiology*; D012137:Respiratory System / Q000503:physiopathology*; D014939:Work of Breathing / Q000502:physiology