Oxygen Saturation Index Guide
What OSI Measures
The oxygen saturation index, often shortened to OSI, compares oxygen support with pulse oximeter saturation. It uses mean airway pressure, inspired oxygen, and SpO2. The value helps show how much ventilator pressure and oxygen are being used to reach a measured saturation. A lower value usually means less support is needed. A higher value can show increased oxygenation difficulty.
Why This Calculator Helps
Manual OSI math is simple, but errors can happen. FiO2 may be typed as a percent or a decimal fraction. Mean airway pressure may be copied from a ventilator screen. SpO2 may change during care. This calculator keeps the inputs clear. It also shows the normalized FiO2 percent, the OSI result, and the SpO2 to FiO2 ratio. These extra values make the result easier to review.
Useful Input Tips
Use values from the same moment whenever possible. Do not mix an earlier oxygen setting with a later saturation reading. Confirm that FiO2 is selected correctly. A value of 0.50 as a fraction equals 50 percent. A value of 50 as a percent also equals 50 percent. Enter mean airway pressure in cmH2O. Enter SpO2 as the pulse oximeter percentage.
Reading The Result
OSI is best used as a trend value. One reading can be useful, but repeated readings show direction better. If OSI rises while settings stay similar, oxygenation may be worsening. If OSI falls, support needs may be improving. Always review the number with the full clinical picture.
Download And Record
The CSV button exports a compact line of data. It is useful for spreadsheets and audit notes. The PDF button creates a printable summary. The example table shows common entries and calculated results. These exports are designed for records, not for replacing clinical documentation.
Important Safety Note
This calculator is educational. It does not diagnose disease. It does not choose oxygen, ventilator, or treatment settings. Pulse oximeters can be affected by motion, perfusion, skin factors, nail products, and device quality. Use professional judgment. Ask a qualified clinician for medical decisions.
Best Review Practice
Compare OSI with notes about position, airway devices, sedation, alarms, and recent suctioning. Small context notes make later review clearer and reduce misunderstanding over time.