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Natural air includes 21% oxygen, which is equivalent to F I O 2 of 0.21. Oxygen-enriched air has a higher F I O 2 than 0.21; up to 1.00 which means 100% oxygen. F I O 2 is typically maintained below 0.5 even with mechanical ventilation, to avoid oxygen toxicity, [2] but there are applications when up to 100% is routinely used.
Positive end-expiratory pressure (PEEP) is the pressure in the lungs (alveolar pressure) above atmospheric pressure (the pressure outside of the body) that exists at the end of expiration. [1] The two types of PEEP are extrinsic PEEP (PEEP applied by a ventilator) and intrinsic PEEP (PEEP caused by an incomplete exhalation).
The oxygenation index is a calculation used in intensive care medicine to measure the fraction of inspired oxygen (FiO2) and its usage within the body. A lower oxygenation index is better - this can be inferred by the equation itself. As the oxygenation of a person improves, they will be able to achieve a higher PaO2 at a lower FiO2.
This is calculated by dividing the PaO2 by the FiO2. Example: patient who is receiving an FiO2 of .5 (i.e., 50%) with a measured PaO2 of 60 mmHg has a PaO 2 / FiO 2 ratio of 120. In healthy lungs, the Horowitz index depends on age and usually falls between 350 and 450.
P high — This is the inspiratory pressure (just like in pressure control). T high — This value is the number of seconds during the inhalation phase. T peep — Also known as the T low, this is the time allotted for expiration. FiO 2 — The fractional O2 percentage of the delivered air-and-oxygen mixture.
The alveolar gas equation is the method for calculating partial pressure of alveolar oxygen (p A O 2). The equation is used in assessing if the lungs are properly transferring oxygen into the blood. The alveolar air equation is not widely used in clinical medicine, probably because of the complicated appearance of its classic forms.
Hypoxemia (also spelled hypoxaemia) is an abnormally low level of oxygen in the blood. [1] [2] More specifically, it is oxygen deficiency in arterial blood. [3] Hypoxemia is usually caused by pulmonary disease. Sometimes the concentration of oxygen in the air is decreased leading to hypoxemia.
In ventilated patients, pulse oximetry is commonly used when titrating FIO2. A reliable target of Spo2 is greater than 95%. [47] The total PEEP in the patient can be determined by doing an expiratory hold on the ventilator. If this is higher than the set PEEP, this indicates air trapping. The plateau pressure can be found by doing an ...