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Sepsis and FIO2

What is sepsis?

sepsis is a severe and potentially life-threatening condition triggered by the body's overwhelming immune response to infection.

There are many biomarkers that directly or indirectly affect sepsis.

Let's learn how FIO2 affect sepsis:-

Fraction of Inspired Oxygen (FiO2) plays a crucial role in the management of patients with sepsis, particularly those who develop sepsis-induced acute respiratory distress syndrome (ARDS).

First of all we need to understand that :-

1. What does the biomarker FiO2 stand for?

❖ FiO2 stands for Fraction of Inspired Oxygen.

❖ It is a measure of the concentration of oxygen in the air that a person breathes.

❖ It is usually expressed as a percentage. For example, if a patient is receiving oxygen with an FiO2 of 50%, it means that 50% of the air they are breathing is pure oxygen.

❖ The FiO2 is a crucial parameter in medical settings, especially in respiratory care, critical care, and anesthesia.

❖ It is used to regulate and monitor the amount of oxygen a patient receives to maintain adequate oxygen levels in the bloodstream.

❖ There are different oxygen delivery devices and flow rates to know, with each device allowing for certain flow rates of oxygen (L/min), as well as different concentrations of oxygen (FIO2).



2. Normal range :-

   The normal range of FiO2 (Fraction of Inspired Oxygen) in ambient air, which is the air we normally breathe, is approximately 21%.

3. How is SEPSIS affected with FiO2 ?

❖ As we all know, Sepsis is a life-threatening condition that arises when the body's response to an infection causes widespread inflammation, leading to organ dysfunction. The management of sepsis includes various supportive measures, and oxygen therapy, including the manipulation of FiO2, plays a crucial role in the care of septic patients.

❖ The specific FiO2 levels and oxygenation targets may vary based on the patient's condition and the severity of sepsis.

❖ FiO2 can be a relevant biomarker in sepsis in the following ways:

1. Respiratory Support: Sepsis can lead to respiratory failure, and patients may have trouble maintaining adequate oxygen levels in their blood. Oxygen therapy with an adjusted FiO2 may be necessary to ensure that the body receives enough oxygen to meet its metabolic demands. The goal is to maintain oxygen saturation levels within the target range.

2. Tissue Oxygenation: Sepsis can cause dysfunction of organs, and maintaining sufficient tissue oxygenation is essential for organ function. Adjusting FiO2 levels may be part of the strategy to optimize oxygen delivery to tissues, especially in cases where sepsis-induced respiratory distress is present.

3. Fluid Resuscitation: In the early stages of sepsis, fluid resuscitation is often a critical intervention. Oxygen therapy, including FiO2 adjustment, supports the overall goal of maintaining tissue oxygenation

4. Monitoring Oxygen Saturation: Continuous monitoring of oxygen saturation (SpO2) is essential in septic patients receiving oxygen therapy. Healthcare providers adjust FiO2 levels based on SpO2 measurements to ensure that oxygen saturation is within the target range.

5. Regular assessment of FiO2 levels: It helps prevent both hypoxemia (low oxygen levels) and Hyperoxemia (excessively high oxygen levels)

Now lets see that :-




4. How do levels of FiO2 affect the various organs present in the body during sepsis?

❖ The effects of FiO2 (Fraction of Inspired Oxygen) levels on organs are primarily related to the balance between providing sufficient oxygen to meet metabolic needs and avoiding potential harm associated with exposure to high concentrations of oxygen.

❖ Oxygen therapy is a critical supportive measure, but excessive oxygen levels should be avoided to minimize the risk of oxygen toxicity and other potential complications.

let’s see how different organs may be affected by varying FiO2 levels:

● Lungs:

● Prolonged exposure to high FiO2 levels, especially above 60-80%, can lead to oxygen toxicity in the lungs. This may result in inflammation and damage to the lung tissues.

For example: Acute Respiratory Distress Syndrome(ARDS).

● Brain:

● Adequate oxygenation is crucial for normal brain function, excessively high FiO2 levels may contribute to vasoconstriction, reducing cerebral blood flow and potentially causing ischemic injury(lack of blood supply to a particular organ).

● The brain is highly sensitive to changes in oxygen levels. Both hypoxemia (low oxygen levels) and hyperoxemia (excessively high oxygen levels) can be detrimental.

● Heart:

● The heart requires a continuous supply of oxygen for proper function. In conditions where there is a reduced oxygen supply to the heart (as in coronary artery disease), providing higher FiO2 levels can help maintain myocardial oxygenation.

● but, prolonged exposure to hyperoxemia may impact coronary blood flow.

● Kidneys:

● The kidneys are generally less sensitive to variations in oxygen levels compared to other organs.

● Adequate oxygen delivery is essential for maintaining renal function. Changes in FiO2 levels can affect oxygen delivery to the kidneys, potentially impacting renal perfusion and function.

● Liver:

The liver is an organ with a high metabolic rate and oxygen demand. Changes in FiO2 can influence hepatic oxygenation. Maintaining adequate oxygen levels is important for preventing ischemic injury to the liver.


5.What are the Symptoms to show the affected levels of Fio2 during sepsis?


❖ The symptoms associated with the affected levels of FiO2 (Fraction of Inspired Oxygen) are primarily related to the respiratory and circulatory consequences of the underlying infection.

❖ Here are some symptoms that may indicate respiratory or circulatory distress during sepsis, which could prompt adjustments in FiO2 levels:

1. Dyspnea: Difficulty Breathing

2. Tachypnea: Increased respiratory rate

3. Low Oxygen Saturation (SpO2)

4. Cyanosis: Bluish discoloration of the skin, lips, or nail beds due to inadequate oxygenation.

5. Altered mental Balance: Confusion or lethargy may indicate impaired oxygen delivery to the brain.

6. Tachycardia: Increased heart rate.

7. Hypotension: Low blood pressure.

8. Decreased urine output.

6 . How do you calculate FiO2?


● The calculation of nasal cannula FiO2 ,

● For the most part, just add 4 for each liter of O2.

● We would obviously do this above room air (21%).

● The only exception to this rule is the first liter (you add 3) – consider this a favor done to get you onto numbers divisible by 4 like this,

Room Air = 21%

1 Liter = 24% (21 + 3)

2 Liters = 28% (24 +4)

3 Liters = 32% (28 +4)

4 Liters = 36% (32+4)

5 Liters = 40% (36+4)

Formula for this is: nFiO2=(Liters∗4)+20


FiO2 (Fraction of Inspired Oxygen) is a crucial parameter in the management of sepsis, ensuring adequate tissue oxygenation and supporting organ function. In septic patients, adjusting FiO2 levels helps maintain oxygen delivery to tissues, stabilize hemodynamics, and support respiratory function.


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Detail explanation about Fio2. Really nice work.

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