\[P_{O_2}=F_{IO_2}\left(P_{atm}-P_{H_2O}\right)\]
Variables
PO2oxygen partial pressure after humidification (mmHg)
FiO2fraction of inspired oxygen
Patmatmospheric pressure (mmHg)
PH2Owater vapor pressure (mmHg)
Description
What is this formula?
The Oxygen Partial Pressure Correction for Humidity calculates the effective oxygen partial pressure after accounting for dilution by water vapor in the respiratory tract.
When to use it
Use this formula when calculating inspired oxygen pressure, performing respiratory physiology studies, evaluating oxygen delivery, or correcting gas measurements for humidification.
Example
Data:
FiO2 = 0.21
Patm = 760 mmHg
PH2O = 47 mmHg
Formula:
PO2 = FiO2(Patm − PH2O)
Substitution:
PO2 = 0.21(760 − 47)
PO2 = 149.7 mmHg
Result:
PO2 ≈ 150 mmHg
Applications
- Pulmonary physiology
- Respiratory therapy
- Gas exchange calculations
- Oxygen delivery assessment
- High-altitude medicine