title: Neurally triggered breaths have reduced response time, work of breathing, and asynchrony compared with pneumatically triggered breaths in a recovering animal model of lung injury.
abstract: OBJECTIVE
  Our objective was to compare response time, pressure time product as a reflection of work of breathing, and incidence and type of asynchrony in neurally vs. pneumatically triggered breaths in a spontaneously breathing animal model with resolving lung injury.
  
  
  METHODS
  Prospective animal study.
  
  
  METHODS
  Experimental laboratory.
  
  
  METHODS
  Male Yorkshire pigs.
  
  
  METHODS
  Intubated, sedated pigs were ventilated using neurally adjusted ventilatory assist and pressure support ventilation with healthy and sick/recruited lungs. After injury, the lung was recruited using a computer-driven protocol. Respiratory mechanics were determined using a forced oscillation technique, and airway flow and pressure waveforms were acquired using a pneumotachograph.
  
  
  RESULTS
  Waveforms were analyzed for trigger delay, pressure time product, and asynchrony. Trigger delay was defined as the time interval (ms) from initiation of a breath to the beginning of ventilator pressurization. Pressure time product was measured as the area of the pressure curve for animal effort (area A) and ventilator response (area B). Asynchrony was classified according to triggering problems, adequacy of flow delivery, and adequate breath termination. Mean values were compared using the Wilcoxon signed-ranks test (p < .05). Trigger delay (ms) was less in neurally triggered breaths (pressure support ventilation healthy 104 ± 27 vs. neurally adjusted ventilatory assist healthy 72 ± 30, pressure support ventilation sick/recruited 77 ± 18 vs. neurally adjusted ventilatory assist sick/recruited 38 ± 18, p < .01). Pressure time product areas A and B were decreased for neurally triggered breaths compared with pressure support ventilation in both healthy and recruited animals (p ≤ .02). Overall, the percentage of asynchrony was less for neurally adjusted ventilatory assist breaths in the recruited animals (pressure support ventilation 27% and neurally adjusted ventilatory assist 6%).
  
  
  CONCLUSIONS
  Neurally triggered breaths have reduced asynchrony, trigger delay, and pressure time product, which may indicate reduced work of breathing associated with less effort to trigger the ventilator and faster response to effort. Further study is required to demonstrate if these differences will lead to decreased days of ventilation and less use of sedation in patients.
authors.affiliation: Section of Critical Care Medicine, Department of Pediatrics, Physiology and Biophysics, University of Arkansas for Medical Sciences College of Medicine, Little Rock, AR, USA. heulittmarkj@uams.edu
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Heulitt
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Clement
authors.forename: Shirley J
authors.initials: SJ
authors.lastname: Holt
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Thurman
authors.forename: Chan-Hee
authors.initials: CH
authors.lastname: Jo
mesh_terms: D055371:Acute Lung Injury / Q000503:physiopathology / Q000628:therapy*; D000465:Algorithms; D000818:Animals; D003964:Diaphragm / Q000502:physiology*; D004195:Disease Models, Animal; D004576:Electromyography; D008297:Male; D011175:Positive-Pressure Respiration / Q000295:instrumentation / Q000379:methods*; D011446:Prospective Studies; D034421:Sus scrofa; D016896:Treatment Outcome; D012122:Ventilators, Mechanical; D014939:Work of Breathing