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


METHODS
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 (FiO2) 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 O2 conserver test system to attempt to predict FiO2 for PF.


RESULTS
Relative volume-averaged FiO2 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. FiO2 values estimated from POC pulse characteristics followed similar trends but were lower than those derived from airway replica experiments.


CONCLUSION
For the POC tested, PF delivered similar, though consistently lower, volume-averaged FiO2 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 FiO2.
['Chen|John Z|JZ|', 'Katz|Ira M|IM|', 'Pichelin|Marine|M|', 'Zhu|Kaixian|K|', 'Caillibotte|Georges|G|', 'Noga|Michelle L|ML|', 'Finlay|Warren H|WH|', 'Martin|Andrew R|AR|']
D000328:Adult D000368:Aged D000072601:Cannula D004867:Equipment Design D015444:Exercise D005260:Female D006801:Humans D008168:Lung D008279:Magnetic Resonance Imaging D008297:Male D008875:Middle Aged D008953:Models, Anatomic D009666:Nose D010102:Oxygen Inhalation Therapy D029424:Pulmonary Disease, Chronic Obstructive D015656:Respiratory Mechanics D012146:Rest D012189:Retrospective Studies D012890:Sleep D013997:Time Factors D014057:Tomography, X-Ray Computed
portable oxygen concentrator (POC) ambulatory oxygen long term oxygen therapy (LTOT)