title: A physiologic comparison of proportional assist ventilation with load-adjustable gain factors (PAV+) versus pressure support ventilation (PSV).
abstract: OBJECTIVE
  To compare patient-ventilator interaction during PSV and PAV+ in patients that are difficult to wean.
  
  
  METHODS
  This was a physiologic study involving 11 patients. During three consecutive trials (PSV first trial--PSV1, followed by PAV+, followed by a second PSV trial--PSV2, with the same settings as PSV1) we evaluated mechanical and patient respiratory pattern; inspiratory effort from excursion Pdi (swing(Pdi)), and pressure-time products of the transdiaphragmatic (PTPdi) pressures. Inspiratory (delay(trinsp)) and expiratory (delay(trexp)) trigger delays, time of synchrony (time(syn)), and asynchrony index (AI) were assessed.
  
  
  RESULTS
  Compared to PAV+, during PSV trials, the mechanical inspiratory time (Ti(flow)) was significantly longer than patient inspiratory time (Ti(pat)) (p < 0.05); Ti(pat) showed a prolongation between PSV1 and PAV+, significant comparing PAV+ and PSV2 (p < 0.05). PAV+ significantly reduced delay(trexp) (p < 0.001). The portion of tidal volume (VT) delivered in phase with Ti(pat) (VT(pat)/VT(mecc)) was significantly higher during PAV+ (p < 0.01). The time of synchrony was significantly longer during PAV+ than during PSV (p < 0.001). During PSV 5 patients out of 11 showed an AI greater than 10%, whereas the AI was nil during PAV+.
  
  
  CONCLUSIONS
  PAV+ improves patient-ventilator interaction, significantly reducing the incidence of end-expiratory asynchrony and increasing the time of synchrony.
authors: Department of Intensive Care and Anaesthesia, Catholic University of Rome, Policlinico Agostino Gemelli, Largo F.Vito 1, 00168 Rome, Italy. roberta.costa@rm.unicatt.it
authors: R
authors: R
authors: Costa
authors: G
authors: G
authors: Spinazzola
authors: F
authors: F
authors: Cipriani
authors: G
authors: G
authors: Ferrone
authors: O
authors: O
authors: Festa
authors: A
authors: A
authors: Arcangeli
authors: M
authors: M
authors: Antonelli
authors: R
authors: R
authors: Proietti
authors: G
authors: G
authors: Conti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D059725:Interactive Ventilatory Support / Q000592:standards*; D008297:Male; D011175:Positive-Pressure Respiration / Q000592:standards*; D015656:Respiratory Mechanics / Q000502:physiology; D012384:Rome; D013990:Tidal Volume / Q000502:physiology; D015919:Ventilators, Negative-Pressure; D014939:Work of Breathing / Q000502:physiology