Partial Pressure Of Oxygen Calculator

Partial Pressure Oxygen Equation:

\[ PO2 = FiO2 \times (P_{atm} - P_{H2O}) \]

Fraction of Inspired Oxygen (FiO2):

(0.21-1.0)

Atmospheric Pressure (P_atm):

mmHg

Water Vapor Pressure (P_H2O):

mmHg

Partial Pressure of Oxygen (PO2):

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1. What is Partial Pressure of Oxygen?

The partial pressure of oxygen (PO2) is the measure of oxygen concentration in a gas mixture or blood. It represents the pressure that oxygen would have if it alone occupied the volume. In respiratory physiology, it's crucial for understanding oxygen delivery to tissues.

2. How Does the Calculator Work?

The calculator uses the alveolar gas equation:

\[ PO2 = FiO2 \times (P_{atm} - P_{H2O}) \]

Where:

\( PO2 \) — Partial pressure of oxygen (mmHg)
\( FiO2 \) — Fraction of inspired oxygen (0.21 for room air to 1.0 for pure oxygen)
\( P_{atm} \) — Atmospheric pressure (760 mmHg at sea level)
\( P_{H2O} \) — Water vapor pressure (47 mmHg at 37°C)

Explanation: The equation calculates the partial pressure of oxygen in inspired air, accounting for water vapor pressure in the airways.

3. Importance of PO2 Calculation

Details: PO2 is essential for assessing respiratory function, determining oxygen delivery to tissues, and managing patients on supplemental oxygen or mechanical ventilation.

4. Using the Calculator

Tips: Enter FiO2 as a decimal (0.21 for room air), atmospheric pressure (760 mmHg at sea level), and water vapor pressure (47 mmHg at body temperature). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is normal PO2 in arterial blood?
A: Normal arterial PO2 is 75-100 mmHg at sea level. Values below 60 mmHg typically indicate hypoxemia.

Q2: How does altitude affect PO2?
A: As altitude increases, atmospheric pressure decreases, reducing PO2 even with the same FiO2.

Q3: What is the difference between PO2 and oxygen saturation?
A: PO2 measures oxygen pressure while oxygen saturation (SpO2) measures the percentage of hemoglobin bound to oxygen.

Q4: Why is water vapor pressure important?
A: Air in the lungs is fully humidified at body temperature, so water vapor pressure reduces the available pressure for oxygen.

Q5: How is this used in clinical practice?
A: This calculation helps predict oxygen levels in the alveoli and is used to adjust ventilator settings and oxygen therapy.