Often asked: How Do You Calculate Pao2 From Fio2?

PaO2 should = FiO2 x 500 (e.g. 0.21 x 500 = 105 mmHg)

How do you calculate PAO2?

The alveolar gas equation is a formula used to approximate the partial pressure of oxygen in the alveolus (PAO2): PAO2=(PB−PH2O)FiO2−(PaCO2÷R) where PB is the barometric pressure, PH2O is the water vapor pressure (usually 47mmHg), FiO2 is the fractional concentration of inspired oxygen, and R is the gas exchange ratio.

What is normal PAO2 FiO2 ratio?

The New P/FP Ratio of 300 to 200 is mild, 200 to 100 is moderate and less than 100 is severe Adult Respiratory Distress Syndrome (ARDS) for all the different levels of PEEP values.

What is the difference between FiO2 and PAO2?

FIO2, the fraction of inspired oxygen in the air, is thus 21% (or. 21) throughout the breathable atmosphere. PaO2 declines with altitude because the inspired oxygen pressure declines with altitude (inspired oxygen pressure is fraction of oxygen times the atmospheric pressure).

How do you calculate P AA O2?

Formula: PAO2 – PaO2 = P(A-a)O2 The Alveolar-arterial gradient (A-a gradient) is a mathematical equation that calculates how difficult it is for oxygen to cross the alveolar-capillary membrane. The equation utilizes two pressures; The partial pressure of oxygen in the alveolus; PAO2 (an estimated measurement)

How do you calculate PAO2 gradient?


  1. PAO2 is the ‘ideal’ compartment alveolar PO2 determined from the alveolar gas equation.
  2. PAO2 = PiO2 – PaCO2/0.8.
  3. A normal A–a gradient for a young adult non-smoker breathing air, is between 5–10 mmHg.
  4. However, the A–a gradient increases with age (see limitations)

How do you calculate SpO2 FiO2 ratio?

In general, Spo2/Fio2 (SF) ratio could be predicted well from pao2/fio2(PF) ratio, using the linear regression equation: SF =57+0.61 PF. Based on this equation a PF ratio of 300 corresponds to SF ratio of 235 and PF ratio of 200 to SF ratio of 181( P <0.001).

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What does FiO2 100 mean?

The flow meter is connected to either a bottle of oxygen or a medical wall supply of oxygen. This oxygen is PURE, it is 100% oxygen! Therefore, anything that comes out of that flow meter has an FiO2 of 100%.

How is PF ratio calculated without ABG?

If your patient’s spo2 = 90%, your patient’s PaO2=60mmHg. If your patient’s spo2=99%, your patient’s PaO2=90mmHg. So if your patient’s SpO2 = 97% and the FiO2=40%, you can estimate the P/F ratio as ~80/0.4=200.

What is PaO2 and PaO2?

With PAO2 representing alveolar oxygen pressure and PaO2 representing arterial oxygen pressure. The arterial oxygen pressure (PaO2) can be directly assessed with an arterial blood gas test (ABG) or estimated with a venous blood gas test (VBG).

What is FiO2 SpO2?

Association Between Peripheral Blood Oxygen Saturation (SpO2)/Fraction of Inspired Oxygen (FiO2) Ratio Time at Risk and Hospital Mortality in Mechanically Ventilated Patients.

How is aa difference calculated?

So there exists a physiologic A-a gradient that changes based on a patient’s age. The expected A-a gradient can be estimated with the following equation: A-a gradient = (Age + 10) / 4.

How do you calculate AA ratio?

Information regarding the alveolar/arterial (A/a) gradient can be estimated indirectly using the partial pressure of oxygen (Po2) (obtained from blood gas analysis) in a simple mathematical formula: A/a gradient = Po2 in alveolar air (estimated from the alveolar gas equation) – Po2 in arterial blood (measured from a

What is PaO2?

Partial pressure of oxygen (PaO2). This measures the pressure of oxygen dissolved in the blood and how well oxygen is able to move from the airspace of the lungs into the blood. Partial pressure of carbon dioxide (PaCO2).