Laboratory Evaluation of Oxygen-Enrichment Methods using a Portable Volume Ventilator

Abstract

Background

This study examined the effects of oxygen (O₂) delivery methods and ventilator settings on the fraction of oxygen delivered (FDO₂) with a portable volume ventilator. DEVICE DESCRIPTION: The Aequitron Medical LP6 is microprocessor-controlled but without an accumulator to provide supplemental O₂. METHODS AND MATERIALS: O₂ at 0.5, 1.0, and 2.0 L/min was (1) bled into the circuit distal to the bacteria filter (B), (2) entrained into the air-inlet filter using an 02 adapter (A), (3) entrained into the air-inlet filter using an O₂ adapter with a reservoir (AR), and (4) provided by the manufacturer's O₂-enrichment kit (EK). FDO₂ was measured with a calibrated O₂ analyzer and recorded at ventilator rates of 10, 12, and 14 cycles/min with 0.5- and 1.0-L tidal volumes (VTs). Multi-way analysis of variance and Fisher's post-hoc test were used to compare FDO₂S among methods.

Results

Over all ventilator rate-Vr combinations and O₂ flowrates, the mean (SD) FDO₂ and low-high ranges were B = 33.5 (6.57)%, 25-48%; A = 26.0 (2.25)%, 23-30%; AR = 31.6 (4.82)%, 25-40%; and EK = 33.6 (7.86), 22-53%. Method B produced the most inconsistent FDO₂ and increased Vr (up to 25%) and peak-inspiratory pressure. These variations were not observed with any of the other methods. For all methods at all settings and O₂ flows, FDO₂ decreased as VT increased but not as rate increased. Difference in FDO₂ among the 4 O₂ enrichment applications was significant (p < 0.005).

Conclusion

Methods AR and EK provide higher and more consistent FDO₂S with less effect on Vr and peak pressure than other methods tested. However, when supplemental oxygen is administered by any of these methods, intermittent O₂ and minute ventilation monitoring is necessary.