Use of a Single Ventilator to Support 4 Patients: Laboratory Evaluation of a Limited Concept

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Abstract:

INTRODUCTION: A mass-casualty respiratory failure event where patients exceed available ventilators has spurred several proposed solutions. One proposal is use of a single ventilator to support 4 patients. METHODS: A ventilator was modified to allow attachment of 4 circuits. Each circuit was connected to one chamber of 2 dual-chambered, test lungs. The ventilator was set at a tidal volume (VT) of 2.0 L, respiratory frequency of 10 breaths/min, and PEEP of 5 cm H2O. Tests were repeated with pressure targeted breaths at 15 cm H2O. Airway pressure, volume, and flow were measured at each chamber. The test lungs were set to simulate 4 patients using combinations of resistance (R) and compliance (C). These included equivalent C and R, constant R and variable C, constant C and variable R, and variable C and variable R. Results. When R and C were equivalent the VT distributed to each chamber of the test lung was similar during both volume (range 428‐442 mL) and pressure (range 528‐544 mL) breaths. Changing C while R was constant resulted in large variations in delivered VT (volume range 257‐621 mL, pressure range 320‐762 mL). Changing R while C was constant resulted in a smaller variation in VT (volume range 418‐460 mL, pressure range 502‐554 mL) compared to only C changes. When R and C were both varied, the range of delivered VT in both volume (336‐517 mL) and pressure (417‐676 mL) breaths was greater, compared to only R changes. CONCLUSIONS: Using a single ventilator to support 4 patients is an attractive concept; however, the VT cannot be controlled for each subject and VT disparity is proportional to the variability in compliance. Along with other practical limitations, these findings cannot support the use of this concept for mass-casualty respiratory failure.

Keywords: mass-casualty; mechanical ventilation; respiratory failure

Document Type: Research Article

DOI: http://dx.doi.org/10.4187/respcare.01236

Publication date: March 1, 2012

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