Oxygen Reserve Index (ORi)

The First Noninvasive & Continuous Parameter to Provide Insight into Oxygen Reserve in Patients Receiving Supplemental Oxygen


Limitations of Current Approaches to Assess Oxygenation

  • > Pulse oximetry (SpO2) provides noninvasive and continuous visibility to arterial blood oxygenation in hypoxia (less than normal oxygenation) and normoxia (normal oxygenation) but cannot assess hyperoxia (higher than normal oxygenation).
  • > During supplemental oxygen administration, clinicians often use the partial pressure of oxygen (PaO2) to monitor levels of hyperoxia but this requires blood gas analysis that is intermittent and delayed.
  • > Between invasive sampling, changes in PaO2 cannot be assessed and therefore unexpected hypoxia or unintended hyperoxia can occur.

Oxygen Reserve Index

  • > ORi is a noninvasive and continuous parameter intended to provide insight into a patient’s oxygen status in the moderate hyperoxic range (PaO2 >100 and ≤ 200 mm Hg) which we define as a patient’s oxygen “reserve”.
  • > ORi is an “index” with a unit-less scale between 0.00 and 1.00
  • > ORi can be trended and has optional alarms to notify clinicians of changes in a patient’s oxygen reserve.
  • > When utilized in conjunction with SpO2 monitoring (as demonstrated in figure 2), ORi may extend the continuous and noninvasive visibility of a patient’s oxygen status into ranges previously unmonitored in this fashion.
  • > ORi is an index that is intended to supplement, not replace, SaO2/SpO2 and PaO2 measurements.

ORi Clinical Application

  • > ORi may be of value in patients receiving supplemental oxygen such as those in surgery, conscious sedation, or in the intensive care unit.
  • > ORi may provide an advance warning of an impending hypoxic state, or an indication of an unintended hyperoxic state when evaluated in conjunction with PaO2.
  • > In this way, ORi may enable proactive interventions to avoid hypoxia and unintended hyperoxia.


Product Display

When used with a rainbow adhesive sensor, ORi can be displayed on Root® with an ORi-enabled Radical-7® with the latest MX-5 circuit board*

Product Specifications

ORi range - 0.00 to 1.00

ORi Accuracy - ≥85% sensitivity and ≥80% specificity to a PaO2 value <150 mm Hg

ORi Alarms - Trending, Low Limit

Technology Platform

Masimo rainbow SET® is a noninvasive monitoring platform featuring Masimo SET® Measure-through Motion and Low Perfusion pulse oximetry with the option to measure multiple additional blood constituents and physiologic parameters.

  • > Oxygen Saturation (SpO2)
  • > Pulse Rate (PR)
  • > Perfusion Index (PI)
  • > Total Hemoglobin (SpHb®)
  • > Oxygen Content (SpOC)
  • > Pleth Variability Index (PVI®)
  • > Methemoglobin (SpMet®)
  • > Carboxyhemoglobin (SpCO®)
  • > Acoustic Respiration Rate (RRa®)
  • > Respiration Rate from the Pleth (RRp)*
  • > Oxygen Reserve Index (ORi)*
  • > Fractional Oxygen Saturation (SpfO2)*

The Root Patient Monitoring and Connectivity also supports measurement expansion through Masimo Open Connect (MOC-9) ports, including:

  • > SedLine® brain function monitoring
  • > Capnography and gas monitoring
  • > O3 regional oximetry*


masimo sedline Brochure:
masimo sedline Whitepaper:

*Regulatory Notice:
The following new features/products are CE Mark and are not currently available for sale in the United States:

  • > Respiration Rate from the Pleth (RRp)
  • > Oxygen Reserve Index (ORi)
  • > Fractional Oxygen Saturation (SpfO2)
  • > O3 Regional Oximetry

For professional use. See instructions for use for full prescribing information, including indications, contraindications, warnings, precautions and adverse events.

ORi is not licensed for sale in Canada.