Work of breathing characteristics of seven portable ventilators☆
Introduction
The intra- and interhospital transport of critically ill patients requiring mechanical ventilation remains a challenge to practitioners. While manual ventilation of these patients with a self-inflating bag has been done of many years, work from our group and others has suggested a portable ventilator (PV) is safer and more likely to maintain ventilatory homeostasis [1], [2], [3]. Portable ventilators have become increasingly sophisticated, offering features once reserved for their intensive care unit (ICU) counterparts.
The imposed work of breathing (WOBI) is the work that must be done by the patient to overcome the resistance of any additional apparatus including the artificial airway, breathing circuit, and ventilator [4]. An excessive WOBI may cause patient discomfort and may lead to respiratory failure [4].
The purpose of this investigation was to compare the WOBI of seven PVs over a range of simulated breathing patterns.
Section snippets
General
Seven PVs were studied — one of each model. These ventilators were selected based on their size, portability, availability, and were acquired from the manufacturer or local hospitals. Table 1 offers a comparison of the various features of the devices.
Each of these ventilators is portable and operates from electrical sources including battery power. Except for the LTV 1000 and Uni-Vent 754, each requires a high pressure oxygen source for operation. The LTV 1000 uses a turbine and the Uni-Vent
Results
The data comparing the seven ventilators are offered in Table 2, Table 3, Table 4. Pressure-volume curves for the seven ventilators during simulated breathing (VT=0.5 l, PIF=60 l/min, PEEP=0 cm H2O, PSV=0 cm H2O) are depicted in Fig. 3. The data comparing the effects of PSV for the Crossvent 4 and LTV 1000, the only two ventilators of the group that offer PSV, are shown in Table 5.
During PSV (with and without PEEP), the delay time, PImax, WOBI, and PTP were lower with the LTV 1000 compared with
Discussion
During the less demanding simulated breathing conditions (VT=0.3 l, PIF=30 l/min and VT 0.5 l, PIF=60 l/min) there were few statistical or clinical differences between the ventilators. However during the most demanding simulated breathing condition (VT=0.8 l, PIF=80 l/min) the delay time, PImax, WOBI, and PTP of the LTV 1000 was statistically less than the other six ventilators. During PSV, the LTV 1000 consistently produced a lower delay time, PImax, WOBI, and PTP compared to the Crossvent 4.
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The views expressed in this article are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense or the US Government.
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The present address for the authors Robert S. Campbell, Jay A. Johannigman and Richard D. Branson is Department of Surgery ML 558, University of Cincinnati Medical Center, 231 Bethesda Ave, Cincinnati, OH 45267-0558, USA.