Chest
Volume 118, Issue 4, October 2000, Pages 1109-1115
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Laboratory and Animal Investigations
Performance of Transport Ventilator With Patient-Triggered Ventilation

https://doi.org/10.1378/chest.118.4.1109Get rights and content

Objectives:

Transport ventilators with inspiratorytriggering functions and pressure support–control modes have recentlybecome commercially available. We evaluated these ventilators incomparison with a standard ICU ventilator.

Studydesign:

Laboratory study with a mechanical lung model.

Methods:

We compared the performance of four transportventilators (model 740, Mallinckrodt, Pleasanton, CA; TBird, BirdProducts 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 simulatedspontaneous breathing (compliance, 46.8 mL/cm H2O;resistance, 5 cm H2O/L/s). The settings of ventilators werepositive end-expiratory pressure (PEEP) of 0 or 5 cm H2O, and pressure support (PS) of 0 or 10 cm H2O. The settingsof the test lung were inspiratory time of 1 s, respiratory rate of10/min, peak inspiratory flow of 40, 60, and 80 L/min. To evaluateinspiratory function at each setting, we measured the inspiratory delaytime (DT), inspiratory trigger pressure (P-I), and the time for airwaypressure to rise from the baseline pressure to 90% of theend-inspiratory pressure (T90%); for expiratory function, supraplateau expiratory pressure (P-E) and the time constant (τe) forpressure decrease during exhalation were evaluated. Oxygen requirementwas assessed as the time required to empty a 3.5-L oxygen tank.

Results:

For inspiratory triggering, four transportventilators had DT < 100 ms, which is considered clinicallysatisfactory, in all the settings except for PS 0 cm H2O, PEEP 0 cm H2O, and inspiratory flow of 80 L/min withLTV1000. P-I increased only in LTV1000 when PEEP was increased from 0to 5 cm H2O. τe for the transport ventilators was>50% shorter than for the ICU ventilator except for PS 0 cmH2O and PEEP 5 cm H2O with TBird. Oxygenrequirement was lowest for the Esprit, followed by the 740, LTV1000,and TBird.

Conclusion:

The newer Food and DrugAdministration–approved transport ventilators have performance indexescomparable to the ventilator currently used in ICUs and can probably berecommended for clinical use.

Section snippets

Lung Model and Ventilators

A custom-made bellows-in-a-box model lung was used to simulatespontaneous breathing (Fig 1). The space between the rigid box and the bellows simulated the pleuralspace. The upper bellows was connected to a metal T-tube through whichgas flow was injected to create negative pressure owing to the Venturieffect in the pleural space. Source gas (air at 50 lb/square inch) wasconnected to a custom-made pressure regulator and a proportionalsolenoid valve (SMC 315; SMC Co; Tokyo, Japan). Opening of the

Results

Figure 3shows typical waveforms for airway pressure plotted against time foreach ventilator when the lung model was set to aninspiratory flow rate of 40 L/min with PEEP set to 5 cmH2O and PS at 10 cm H2O.

For each of the ventilators in this study, Table 2presents data for the variables shown in Figure 2. The Esprit showedintractable self-triggering at inspiratory flow of 60 and 80 L/min, andresults that were affected by this were excluded from analysis.

During inspiration, DT at inspiratory phase

Discussion

The major findings of this study are that (1) the transportventilators we evaluated trigger inspiration well enough to synchronizewith the breathing of patients; (2) the transport ventilators had evenlower expiratory resistance than a standard ICU ventilator; and (3) the Esprit had the lowest oxygen requirement, followed by the 740, the LTV, and the TBird.

Mechanically ventilated critically ill patients of ten require transportto perform diagnostic or therapeutic procedures that cannot

References (12)

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Supported by departmental funding. Ventilators were provided by FujiRespiratory Care Co., Ltd. and Mallinckrodt Japan Co., Ltd.

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