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      Comparison of pulsed versus continuous oxygen delivery using realistic adult nasal airway replicas

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          Portable oxygen concentrators (POCs) typically include pulse flow (PF) modes to conserve oxygen. The primary aims of this study were to develop a predictive in vitro model for inhaled oxygen delivery using a set of realistic airway replicas, and to compare PF for a commercial POC with steady flow (SF) from a compressed oxygen cylinder.


          Experiments were carried out using a stationary compressed oxygen cylinder, a POC, and 15 adult nasal airway replicas based on airway geometries derived from medical images. Oxygen delivery via nasal cannula was tested at PF settings of 2.0 and 6.0, and SF rates of 2.0 and 6.0 L/min. A test lung simulated three breathing patterns representative of a chronic obstructive pulmonary disease patient at rest, during exercise, and while asleep. Volume-averaged fraction of inhaled oxygen (F iO 2) was calculated by analyzing oxygen concentrations sampled at the exit of each replica and inhalation flow rates over time. POC pulse volumes were also measured using a commercial O 2 conserver test system to attempt to predict F iO 2 for PF.


          Relative volume-averaged F iO 2 using PF ranged from 68% to 94% of SF values, increasing with breathing frequency and tidal volume. Three of 15 replicas failed to trigger the POC when used with the sleep breathing pattern at the 2.0 setting, and four of 15 replicas failed to trigger at the 6.0 setting. F iO 2 values estimated from POC pulse characteristics followed similar trends but were lower than those derived from airway replica experiments.


          For the POC tested, PF delivered similar, though consistently lower, volume-averaged F iO 2 than SF rates equivalent to nominal PF settings. Assessment of PF oxygen delivery using POC pulse characteristics alone may be insufficient; testing using airway replicas is useful in identifying possible cases of failure and may provide a better assessment of F iO 2.

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          Most cited references 33

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          The effects of high-flow vs low-flow oxygen on exercise in advanced obstructive airways disease.

          Current options to enhance exercise performance in patients with COPD are limited. This study compared the effects of high flows of humidified oxygen to conventional low-flow oxygen (LFO) delivery at rest and during exercise in patients with COPD.
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            Delivered oxygen concentrations using low-flow and high-flow nasal cannulas.

            Nasal cannulas are commonly used to deliver oxygen in acute and chronic care settings; however, there are few data available on delivered fraction of inspired oxygen (F(IO(2))). The purposes of this study were to determine the delivered F(IO(2)) on human subjects using low-flow and high-flow nasal cannulas, and to determine the effects of mouth-closed and mouth-open breathing on F(IO(2)). We measured the pharyngeal F(IO(2)) delivered by adult nasal cannulas at 1-6 L/min and high-flow nasal cannulas at 6-15 L/min consecutively in 10 normal subjects. Oxygen was initiated at 1 L/min, with the subject at rest, followed by a period of rapid breathing. Gas samples were aspirated from a nasal catheter positioned with the tip behind the uvula. This process was repeated at each liter flow. Mean, standard deviation, and range were calculated at each liter flow. F(IO(2)) during mouth-open and mouth-closed breathing were compared using the dependent test for paired values, to determine if there were significant differences. The mean resting F(IO(2)) ranged from 0.26-0.54 at 1-6 L/min to 0.54-0.75 at 6-15 L/min. During rapid breathing the mean F(IO(2)) ranged from 0.24-0.45 at 1-6 L/min to 0.49-0.72 at 6-15 L/min. The mean F(IO(2)) increased with increasing flow rates. The standard deviation (+/- 0.04-0.15) and range were large, and F(IO(2)) varied widely within and between subjects. F(IO(2)) during mouth-open breathing was significantly (p < 0.05) greater than that during mouth-closed breathing. F(IO(2)) increased with increasing flow. Subjects who breathed with their mouths open attained a significantly higher F(IO(2)), compared to those who breathed with their mouths closed.
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              Evaluation of five oxygen delivery devices in spontaneously breathing subjects by oxygraphy.

               T Waldau,  V LARSEN,  J Bonde (1998)
              Oxygen supply systems may be divided into constant and variable performance systems. As the variable performance systems are widely used, it is relevant to investigate the variation in performance between devices and the influence of oxygen supply on the inspired oxygen fraction. Data were collected from 10 healthy volunteers during the use of one constant performance system and four variable performance systems at different gas flows and inspired oxygen fractions. A thin sampling catheter was placed in the nasopharynx to allow the measurement of the end-tidal oxygen fraction. When oxygen was supplied to variable performance systems, end-tidal oxygen fraction values measured in this way varied less and were more easily quantifiable than inspired oxygen fraction. End-tidal oxygen fraction was used to calculate inspired oxygen fraction. With the variable performance systems, inspired oxygen fraction varied considerably between subjects whereas a constant and equal rise was found for each subject with the fixed performance system. A large nasal catheter was capable of delivering the highest inspired oxygen fraction, whereas the Venturi mask delivered the most precise inspired oxygen fraction. We found oxygraphy useful in the interpretation of measurements made in patients receiving unknown inspired fractions of oxygen.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                24 August 2017
                : 12
                : 2559-2571
                [1 ]Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada
                [2 ]Medical R&D, Air Liquide Santé International, Centre de Recherche Paris-Saclay, Les Loges-en-Josas
                [3 ]Centre Explor!, Air Liquide Healthcare, Gentilly, France
                [4 ]Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB, Canada
                Author notes
                Correspondence: Andrew R Martin, 10-324, Donadeo Innovation Centre for Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada, Tel +1 780 492 9012, Email andrew.martin@
                © 2017 Chen et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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