Background With noninvasive positive pressure ventilation (NPPV), the fraction of delivered oxygen ( F DO 2 '') can change if other ventilatory parameters are altered, but the extent and precise nature of the relationship between F DO 2 '' and other ventilatory parameters is not well understood. Methods We studied a new NPPV device, the Quantum PSV (Respironics Inc, Marietta, Georgia) to measure changes in the F DO 2 '' with changes in 4 ventilatory parameters: (1) inspiratory pressure, (2) expiratory pressure, (3) inspiratory time fraction (T₁), and (4) insertion point of supplemental oxygen. Results Each oxygen L/min increase yielded a 0.05-0.06 increase in the oxygen concentration delivered to the test lung. Changing the site of oxygen introduction resulted in a 0.04-0.10 increase in mean F DO 2 ''. Comparing mean F DO 2 '' values from both oxygen introduction sites yielded p-values F DO 2 '' values of 0.71 and 0.48 respectively at 10 L/min O₂, and 0.98 and 0.70 at 15 L/min O₂. When data from all 4 inspiratory positive airway pressure-expiratory positive airway pressure (IPAP-EPAP) combinations were pooled, F DO 2 '' was significantly higher with T₁ = 0.25 than with T₁ = 0.35 (p F DO 2 ''. Introducing oxygen into the patient circuit at the point most distant from the patient (nearest to the ventilator) provided higher F DO 2 '' values than when oxygen was inserted near the mask, but adding oxygen at the dis
Waugh et al. (Sat,) studied this question.
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