title: Influences of Duration of Inspiratory Effort, Respiratory Mechanics, and Ventilator Type on Asynchrony With Pressure Support and Proportional Assist Ventilation.
abstract: BACKGROUND
  Pressure support ventilation (PSV) is often associated with patient-ventilator asynchrony. Proportional assist ventilation (PAV) offers inspiratory assistance proportional to patient effort, minimizing patient-ventilator asynchrony. The objective of this study was to evaluate the influence of respiratory mechanics and patient effort on patient-ventilator asynchrony during PSV and PAV plus (PAV+).
  
  
  METHODS
  We used a mechanical lung simulator and studied 3 respiratory mechanics profiles (normal, obstructive, and restrictive), with variations in the duration of inspiratory effort: 0.5, 1.0, 1.5, and 2.0 s. The Auto-Trak system was studied in ventilators when available. Outcome measures included inspiratory trigger delay, expiratory trigger asynchrony, and tidal volume (VT).
  
  
  RESULTS
  Inspiratory trigger delay was greater in the obstructive respiratory mechanics profile and greatest with a effort of 2.0 s (160 ms); cycling asynchrony, particularly delayed cycling, was common in the obstructive profile, whereas the restrictive profile was associated with premature cycling. In comparison with PSV, PAV+ improved patient-ventilator synchrony, with a shorter triggering delay (28 ms vs 116 ms) and no cycling asynchrony in the restrictive profile. VTwas lower with PAV+ than with PSV (630 mL vs 837 mL), as it was with the single-limb circuit ventilator (570 mL vs 837 mL). PAV+ mode was associated with longer cycling delays than were the other ventilation modes, especially for the obstructive profile and higher effort values. Auto-Trak eliminated automatic triggering.
  
  
  CONCLUSIONS
  Mechanical ventilation asynchrony was influenced by effort, respiratory mechanics, ventilator type, and ventilation mode. In PSV mode, delayed cycling was associated with shorter effort in obstructive respiratory mechanics profiles, whereas premature cycling was more common with longer effort and a restrictive profile. PAV+ prevented premature cycling but not delayed cycling, especially in obstructive respiratory mechanics profiles, and it was associated with a lower VT.
authors.affiliation: Federal University of Ceará, Fortaleza, Brazil. renatavasconcelos23@gmail.com.
authors.forename: Renata S
authors.initials: RS
authors.lastname: Vasconcelos
authors.affiliation: Federal University of Ceará, Fortaleza, Brazil.
authors.forename: Raquel P
authors.initials: RP
authors.lastname: Sales
authors.affiliation: Federal University of Ceará, Fortaleza, Brazil.
authors.forename: Luíz H de P
authors.initials: LHP
authors.lastname: Melo
authors.affiliation: Federal University of Ceará, Fortaleza, Brazil.
authors.forename: Liégina S
authors.initials: LS
authors.lastname: Marinho
authors.affiliation: Federal University of Ceará, Fortaleza, Brazil.
authors.forename: Vasco Pd
authors.initials: VP
authors.lastname: Bastos
authors.affiliation: Federal University of Ceará, Fortaleza, Brazil.
authors.forename: Andréa da Nc
authors.initials: ADN
authors.lastname: Nogueira
authors.affiliation: University of São Paulo School of Medicine, São Paulo, Brazil.
authors.forename: Juliana C
authors.initials: JC
authors.lastname: Ferreira
authors.affiliation: Federal University of Ceará, Fortaleza, Brazil.
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Holanda
mesh_terms: D006801:Humans; D001239:Inhalation; D059725:Interactive Ventilatory Support / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D008953:Models, Anatomic; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume; D013997:Time Factors; D012122:Ventilators, Mechanical / Q000009:adverse effects*
keywords: ARDS; COPD; artificial respiration; mechanical ventilators; respiratory mechanics