Comparison of pulsed flow from portable oxygen concentrators with continuous oxygen delivery.

Abstract

Introduction: Portable oxygen concentrators (POCs) deliver oxygen in pulses triggered by inspiration. The challenge of establishing equivalence between continuous flow oxygen (CFO) and nominal pulse flow (PF) settings on different POCs is well known. Aims and Objectives: A combination of bench measurements and mathematical modeling was used to compare the performance of four POCs versus CFO by predicting the fraction of inspired oxygen (FiO2) at the trachea and entering the acini. Methods: Each of four POCs was connected via nasal cannula to a 3D-printed replica of a human adult nasal airway. A test lung simulated three breathing patterns representative of a COPD patient at rest, during exercise and while asleep. Volume-averaged tracheal FiO2 was calculated by analyzing oxygen concentrations and inhalation flow rates over time. To describe transport of oxygen through the lower respiratory tract to the acini, a single-path mathematical model of the conducting airways was used. Results: CFO consistently delivered significantly greater tracheal FiO2 (>2% absolute) for all nominally equivalent PF settings greater than 2. Significant differences between POCs operating in PF were observed, particularly at high device settings. Model calculations showed that efficiency of delivery to the acini was higher in PF than in CFO, but that CFO generally delivered a higher absolute volume of oxygen. Conclusions: Significant differences in oxygen delivery were found between PF and CFO, and between PF modes in different POCs. While PF is a more efficient mode of delivery than CFO, for the POCs tested CFO resulted in a greater absolute volume of oxygen delivered per breath.