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limited in this regard, because it lacks a battery and needs compressed gas to operate.

Issues/Problems With Specific Ventilators

controls, and the manufacturer’s specified patient-weight range was outside the weight range of the animals we used. However, it is the smallest and lightest of the ven- tilators we tested, and it is only for single-patient use.

The choice of a ventilator is also determined by other specific design issues. Only 2 of the ventilators (Bio-Med Devices IC2 and Oceanic Medical Products Magellan) are designed for use during magnetic resonance imaging. The following ventilators had no alarms: Vortran RespirTech Pro, Bio-Med Devices IC2, Percussionaire TXP, Oceanic Medical Products Magellan, and Life Support Products AutoVent 2000.

It may be necessary with some of these ventilators to monitor gas delivery with a secondary monitor because of the large difference between the set and actual VT and RR. Since we did not assess these ventilators during spontane- ous breathing, we cannot comment on patient-ventilator synchrony or the difference between the set and delivered parameters during spontaneous ventilation.

Comparison With Other Studies

Many of the ventilators allow very few FIO2 values: Vor- tran RespirTech Pro (FIO2 1.0), Bio-Med Devices IC2 (FIO 1.0), Oceanic Medical Products Magellan 2000 (FIO2 1.0), Pneupac Parapac Transport 200D (FIO2 0.5 or 1.0), Pneupac Parapac Medic (FIO2 0.5 or 1.0), Bio-Med Devices Cross- 2

vent 3 (FIO2 0.5 or 1.0), Carevent ATV(F and Life Support Products AutoVent 2000 (F IO2 IO2

0.8 or 1.0), 1.0).

The oxygen cylinder life of the Pneupac Parapac Medic exceeded the maximum estimated time (66 min), because VT gradually decreased as the cylinder became depleted to 200 mL just before the ventilator shut down.

With the Percussionaire TXP, the maximum FIO2 deliv- ered was 0.5, which accounts for its 77-min cylinder life. Note, however, that the volume of gas in E-size cylinders does vary, because filling pressure varies, which adds to the variability in cylinder life.

With the Newport HT50 and its nondisposable propri- etary circuit, intrinsic PEEP developed at higher RR be- cause of high expiratory resistance. With the Bio-Med Devices IC2, Life Support Products Magellan 2000, Pneu- pac Parapac Transport 200D, and Pneupac Parapac Medic the VT is set with the flow rate and TI controls, and RR is controlled by those two plus an expiratory time control. With the Carevent ATV, VT is determined by V˙ E and RR. The Life Support Products AutoVent 2000 has 2 con- trols (RR and VT), its maximum RR is 18 breaths/min, and it does not have any alarms. The Pneupac Compac 200 is designed for military use. It has a sturdy case, and VT is

˙ adjusted by setting VE and RR. It has a fixed TI of 1 s and

a maximum RR of 26 breaths/min. The Percussionaire TXP is a pressure-limited and time-cycled ventilator, and its VT varied with changes in impedance, but we found that even with constant impedance the VT drifted upwards.

Nolan et al5 evaluated the performance of 6 pneumati- cally operated ventilators. Similar to our results, they noted that the overall ability of the ventilators they tested to maintain delivered VT, V˙ E, and RR consistent with the set levels diminished as resistance increased or compliance decreased. McGough et al6 observed the same problem with 8 pneumatically operated ventilators they evaluated with a test lung. The Univent 750 was evaluated by Camp- bell et al,7 with a test lung, during controlled and patient- triggered ventilation. They observed, as we did, that with the Univent Eagle 754, gas delivery was not markedly affected by a decrease in compliance or an increase in resistance.

More recently, Miyoshi et al8 evaluated 4 ventilators with transport capabilities, all with internal batteries. How- ever, at least 3 of these units (Puritan Bennett 740, Bird T-Bird, and Respironics Espirit) would not be considered typical transport ventilators. However, all of these units, along with the Pulmonetic Systems LTV 1000, were ca- pable of ventilating a test lung during assisted ventilation, at various ventilation settings.

Zanetta et al9 evaluated 5 transport ventilators and 3 intensive care unit ventilators during controlled and pa- tient-triggered ventilation with a test lung. They deter- mined that VT varied 10% as delivered VT varied from 300 mL to 800 mL and compliance and resistance were varied. However, they noted that, because of high resis- tance to exhalation, all the portable ventilators they eval- uated trapped gas at high V˙ E.


The maximum RR with the Life Support Products AutoVent 2000 is 18 breaths/min, and with the Carevent ATVit is 40 breaths/min. With the Oceanic Medical Products Magellan, setting RR at 15 breaths/min and 20 breaths/min resulted in measured RR of 23 breaths/min and 30 breaths/min, respectively.

The most difficult ventilator to evaluate was the Vortran RespirTech Pro. This ventilator has few clearly labeled

The primary limitation of the present study is that it was not performed with patients. However, the bench and an- imal evaluations did simulate common settings required by patients during controlled ventilation. In addition, the animal model evaluations were consistent with pediatric patients, not adults. This limited the assessment of some of the ventilators. We also did not evaluate any of these ventilators during spontaneous breathing, which is clearly



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