Synchronization of oxygen delivery with breathing pattern for enhanced comfort: a bench study

Respir Care. 2013 Mar;58(3):498-506. doi: 10.4187/respcare.01851.


Background: Oxygen has been widely used for COPD patients because long-term oxygen therapy can improve survival duration of COPD patients with severe hypoxemia. The typical oxygen delivery methods used for long-term oxygen therapy are continuous flow oxygen (CFO) and demand oxygen delivery (DOD). Currently, DOD is preferred to CFO in oxygen conserving devices because waste of oxygen is substantial in CFO. However, DOD causes discomfort to patients since it abruptly supplies high-flow oxygen during inhalation only.

Methods: To overcome the drawbacks of CFO and DOD, we developed a novel oxygen delivery method, synchronized DOD (SDOD), which can reduce waste oxygen and patient discomfort. We used the concept of "jerk" from physics, which indicates the rate of change of acceleration, and defined a discomfort index (DI) to quantitatively represent the degree of discomfort. To determine the correlation between DI and the actual human feeling of discomfort, we tested subjects' responses to different levels of DI. Moreover, depending on the level of oxygen saving of each method, CFO, DOD, and SDOD regions were identified in a prescription flow/supply flow plane. A bench study was conducted to experimentally compare the Fio2 between CFO and SDOD at 20 breaths/min.

Results: The results of this study illustrate that there is a region of compromise between oxygen saving and patient comfort that is filled by SDOD. DI is positively correlated with actual human discomfort (P < .001). In addition, the DI of SDOD was much lower than that of DOD. Fio2 of SDOD was 2-5% less than that of CFO.

Conclusions: In conclusion, SDOD might provide more comfortable oxygen delivery by reducing DI, and conserves oxygen while offering an equivalent Fio2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Inhalation
  • Algorithms
  • Humans
  • Hypoxia / therapy
  • Oxygen / administration & dosage
  • Oxygen Inhalation Therapy / methods*
  • Pulmonary Disease, Chronic Obstructive / therapy*


  • Oxygen