FiO2
Encyclopedia
FiO2, in the field of medicine
, is the fraction of inspired oxygen
in a gas mixture.
The FiO2 is expressed as a number from 0 (0%) to 1 (100%).
The FiO2 of normal room air is 0.21 (21%).
A patient's FiO2 may be varied through the use of different Venturi mask
s, in combination with varying oxygen flow rates. In addition, most mechanical ventilators have controls for adjusting FiO2. An increased FiO2 is necessary in managing adequate oxygenation in patients who are critically ill due to causes such as major surgery
, acute lung injury
, sepsis
, pneumonia
, congestive heart failure
, or other cardiopulmonary disease. The oxygenation to a patient on a ventilator can be manipulated by changing not only FiO2, but also the tidal volume,the respiratory rate and having a positive end-expiratory pressure
(PEEP). Generally the FiO2 is maintained at less than 60%. Higher settings can lead to oxygen toxicity
.
Another common misconception is that the FiO2 changes with elevation. It remains at 0.21 at all altitudes within the atmosphere. What changes is the barometric pressure of air. At altitude, therefore, the partial pressure
of oxygen delivered by that 21% of oxygen is lower. The partial pressure is the driving force to oxygenate the blood and therefore a lower partial pressure makes it that much harder to get O2 delivered to the tissues that require it, resulting in hypoxia
.
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, is the fraction of inspired oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
in a gas mixture.
The FiO2 is expressed as a number from 0 (0%) to 1 (100%).
The FiO2 of normal room air is 0.21 (21%).
A patient's FiO2 may be varied through the use of different Venturi mask
Venturi mask
The venturi mask, also known as an air-entrainment mask, is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy. Venturi masks are considered high-flow oxygen therapy devices. This is because venturi masks are able to provide total inspiratory flow at a...
s, in combination with varying oxygen flow rates. In addition, most mechanical ventilators have controls for adjusting FiO2. An increased FiO2 is necessary in managing adequate oxygenation in patients who are critically ill due to causes such as major surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
, acute lung injury
Acute lung injury
Acute lung injury is a diffuse heterogeneous lung injury characterized by hypoxemia, non cardiogenic pulmonary edema, low lung compliance and widespread capillary leakage...
, sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
, pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
, congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
, or other cardiopulmonary disease. The oxygenation to a patient on a ventilator can be manipulated by changing not only FiO2, but also the tidal volume,the respiratory rate and having a positive end-expiratory pressure
Positive end-expiratory pressure
Positive end-expiratory pressure is the pressure in the lungs above atmospheric pressure that exists at the end of expiration...
(PEEP). Generally the FiO2 is maintained at less than 60%. Higher settings can lead to oxygen toxicity
Oxygen toxicity
Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen at elevated partial pressures. It is also known as oxygen toxicity syndrome, oxygen intoxication, and oxygen poisoning...
.
Another common misconception is that the FiO2 changes with elevation. It remains at 0.21 at all altitudes within the atmosphere. What changes is the barometric pressure of air. At altitude, therefore, the partial pressure
Partial pressure
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....
of oxygen delivered by that 21% of oxygen is lower. The partial pressure is the driving force to oxygenate the blood and therefore a lower partial pressure makes it that much harder to get O2 delivered to the tissues that require it, resulting in hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
.