Objectives: Transport ventilators with inspiratory triggering functions and pressure support-control modes have recently become commercially available. We evaluated these ventilators in comparison with a standard ICU ventilator.
Study design: Laboratory study with a mechanical lung model.
Methods: We compared the performance of four transport ventilators (model 740, Mallinckrodt, Pleasanton, CA; TBird, Bird Products Corp, Palm Springs, CA; LTV1000, Pulmonetic Systems, Colton, CA; Esprit, Respironics, Vista, CA) with a standard ICU ventilator (model 7200ae; Mallinckrodt) using a test lung that simulated spontaneous breathing (compliance, 46.8 mL/cm H(2)O; resistance, 5 cm H(2)O/L/s). The settings of ventilators were positive end-expiratory pressure (PEEP) of 0 or 5 cm H(2)O, and pressure support (PS) of 0 or 10 cm H(2)O. The settings of the test lung were inspiratory time of 1 s, respiratory rate of 10/min, peak inspiratory flow of 40, 60, and 80 L/min. To evaluate inspiratory function at each setting, we measured the inspiratory delay time (DT), inspiratory trigger pressure (P-I), and the time for airway pressure to rise from the baseline pressure to 90% of the end-inspiratory pressure (T(90%)); for expiratory function, supraplateau expiratory pressure (P-E) and the time constant (taue) for pressure decrease during exhalation were evaluated. Oxygen requirement was assessed as the time required to empty a 3.5-L oxygen tank.
Results: For inspiratory triggering, four transport ventilators had DT < 100 ms, which is considered clinically satisfactory, in all the settings except for PS 0 cm H(2)O, PEEP 0 cm H(2)O, and inspiratory flow of 80 L/min with LTV1000. P-I increased only in LTV1000 when PEEP was increased from 0 to 5 cm H(2)O. taue for the transport ventilators was > 50% shorter than for the ICU ventilator except for PS 0 cm H(2)O and PEEP 5 cm H(2)O with TBird. Oxygen requirement was lowest for the Esprit, followed by the 740, LTV1000, and TBird.
Conclusion: The newer Food and Drug Administration-approved transport ventilators have performance indexes comparable to the ventilator currently used in ICUs and can probably be recommended for clinical use.