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.
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