title: Lower back-up rates improve ventilator triggering during assist-control ventilation: a randomized crossover trial.
abstract: OBJECTIVE
  The objective of this study is to compare the effects of back-up ventilation rates (BURs) on triggered inflations and patient cardiorespiratory stability during assist-control/volume guarantee ventilation (AC/VG).
  
  
  METHODS
  This study is a randomized crossover trial conducted in a neonatal unit in an Australian tertiary NICU. In all, 26 stable preterm infants on AC/VG ventilation were studied at BUR settings of 30, 40 and 50 min(-1). Inflation rate, triggering and cardiorespiratory measures of patient stability were compared during 20 min epochs with 10 min washout periods.
  
  
  RESULTS
  The 26 infants studied were median (inter-quartile range) gestational age 27 (26, 30) weeks, birth weight 0.84 (0.75, 1.14) kg and FiO(2) 0.24 (0.21, 0.31) and age 6 (4, 19) days. At BURs of 30, 40 and 50, the proportions of inflations, which were triggered, were mean (s.d.) 85% (11), 75% (19) and 61% (25); P<0.01 for all comparisons. Total delivered inflation rates were 56 (8), 58 (9) and 62 (8) min(-1), respectively. Cardiorespiratory parameters did not vary between the settings.
  
  
  CONCLUSIONS
  Using a lower BUR allows greater triggering of ventilator inflations. Cardiorespiratory parameters including CO(2) levels were stable at all rates.
authors.affiliation: Newborn Research, The Royal Women's Hospital, Melbourne, Victoria, Australia. kevin.wheeler@thewomens.org.au
authors.forename: K I
authors.initials: KI
authors.lastname: Wheeler
authors.forename: C J
authors.initials: CJ
authors.lastname: Morley
authors.forename: S B
authors.initials: SB
authors.lastname: Hooper
authors.forename: P G
authors.initials: PG
authors.lastname: Davis
mesh_terms: D001315:Australia; D001724:Birth Weight; D018592:Cross-Over Studies; D005260:Female; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007363:Intensive Care Units, Neonatal; D008297:Male; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000295:instrumentation* / Q000379:methods; D012131:Respiratory Insufficiency / Q000175:diagnosis / Q000628:therapy*; D015656:Respiratory Mechanics; D018570:Risk Assessment; D013990:Tidal Volume / Q000502:physiology*; D013997:Time Factors; D016896:Treatment Outcome; D015300:Ventilator Weaning; D012122:Ventilators, Mechanical / Q000706:statistics & numerical data