The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Robert L. Joyner1, Sidney R. Schneider1, Anne Preas1, Matthew Ng1

Background: There is a paucity of data comparing indicators of work-of breathing and patient-ventilator synchrony (PVS) in turbine-based non-invasive ventilators. Time-delay (TDx) to pressurization, pressure-time-product (PTP), and breath type delivered were used to evaluate parameters of WOB and PVS in a test lung model.

Methods: Parameters of inspiratory WOB were evaluated by assessing the inspiratory trigger time-delay (TD1), time-delay in return to baseline (TD2), and pressure-time product (PTP). PVS was evaluated by identifying triggered, auto-triggered, and missed breath types delivered during experimental conditions. Six non-invasive turbine-based ventilators were tested: Vision (Respironics); BiPAP Focus (Respironics); Vela (Viasys Healthcare); iVent (VersaMed); LTV 1200 (Viasys Healthcare); Carina (Dräger Medical). Data from tested ventilators were evaluated with a spontaneous breathing lung model with compliance=0.065 L/cm H2O and Raw=28.24 cm H2O/L/sec. Spontaneous breathing was simulated with a driving ventilator set to deliver PCV=40 cm H2O; f=12 bpm; I-time=0.8 sec; inspiratory rise-time 0.1 sec; PEEP=18 cm H2O; FIO2=0.21. Each tested ventilator was evaluated using settings: IPAP=15 cm H2O; EPAP=5 cm H2O; FIO2=0.21. All pressure and flow data were collected at the proximal airway with a CO2SMO Plus respiratory mechanics monitor (Novametrix) for two minutes. TD1, TD2, and PTP data were collected from ten iterations of 2 minute periods during conditions of no leak. Breath-type delivered data were collected during ten iterations of six sequential conditions: no leak, small leak, no leak, moderate leak, no leak, large leak, and no leak. Significance was set at p?0.05. Values expressed in means with 95% confidence intervals.

Results: One-way ANOVAs compared differences among ventilators for TD1, TD2, PTP, and breath type. Compared to all other ventilators tested, the iVent had the greatest length of time required to begin pressurization (TD1+TD2); the iVent exhibited the largest PTP, and the Vela and the LTV1200 exhibited the largest number of dys-synchronous breaths (i.e., auto-triggered, missed) when compared across conditions.

Conclusion: Evaluating non-invasive ventilator performance requires an understanding of the complex interaction between the patient the ventilator. Knowledge of the parameters associated with induced WOB as well as breath type delivery is necessary to understand the overall performance of the ventilator.