The Fraction of Inspired Oxygen (FiO2) is a crucial parameter in respiratory therapy, as it measures the concentration of oxygen a patient receives. Accurate calculation of FiO2 ensures appropriate usage of oxygen therapy devices to aid patients experiencing respiratory issues. This article will guide you through the process of calculating FiO2 based on various methods.

1. Nasal Cannula:

Nasal cannulas are one of the most common devices used to administer oxygen. The level of provided oxygen is incremented by 4% for each liter per minute (L/min) of flow rate. Be aware that room air contains approximately 21% oxygen.

Formula: FiO2 = 21% + (4% x L/min)

Example: If a patient is on 3 L/min of oxygen via nasal cannula, the FiO2 can be calculated as follows:

FiO2 = 21% + (4% x 3)

FiO2 = 21% + 12%

FiO2 = 33%

2. Simple Face Mask:

Simple face masks deliver between 35% and 50% oxygen concentration depending on the flow rate. To estimate the FiO2 accurately, follow this formula:

Formula: FiO2 = (35-50)% with flow rates ranging from 6–12 L/min

Specify the amount within the given range based on your priority assessment.

3. Non-Rebreather Mask (NRBM):

A non-rebreather mask provides high levels of oxygen concentration ranging from 80% to 100%. The bag attached to the mask should remain inflated during inspiration, and the valves should prevent exhaled air from reentering the mask.

Formula: FiO2 = (80-100)% with flow rates ranging from 10–15 L/min

Adjust within this range according to your patient’s requirements.

4. Ventimask:

Also known as “high-flow” masks, Ventimasks deliver oxygen concentrations of 24% to 60%. Each colored adapter corresponds to a precise FiO2 level, making calculations straightforward.

Method: Check the manufacturer’s guidelines for specific adapters and their corresponding FiO2 levels.

5. Mechanical Ventilation:

In mechanically ventilated patients, FiO2 refers to the concentration of oxygen delivered by the breathing machine. The fractional concentration is typically manipulated directly on the device, expressed as a decimal.

Example: If you set the FiO2 at 0.50 on the ventilator, it means that the patient receives 50% inspired oxygen.

Conclusion:

Accurate calculation of FiO2 is essential in delivering appropriate oxygen therapy to patients with respiratory problems. It’s crucial to carefully monitor and adjust FiO2 levels based on individual requirements. Keep in mind that these methods are mere guidelines; always refer to specific device instructions when applicable, and consult healthcare professionals while implementing adjustments.