In a situation where a diver is using EANx30 at 30 meters, what is the partial pressure of oxygen (PO2)?

To determine the partial pressure of oxygen (PO2) when using EANx30 (Enriched Air Nitrox with 30% oxygen) at a depth of 30 meters, one must first understand how partial pressures are calculated in diving.

At any depth, the total pressure increases due to the weight of the water above. The total pressure at a depth of 30 meters is typically about 4.0 atmospheres (3 atmospheres for the water column plus 1 atmosphere for the surface). This can be calculated using the formula:

Total pressure = Surface pressure + (Water pressure) Total pressure at 30m = 1 atm + (depth in meters / 10)

Using EANx30, which consists of 30% oxygen, the partial pressure of oxygen is calculated by multiplying the total pressure by the fraction of oxygen in the gas mixture:

PO2 = Total pressure × Fraction of oxygen

For EANx30: Fraction of oxygen = 0.30 Total pressure at 30 meters ≈ 4.0 atm

Therefore: PO2 = 4.0 atm × 0.30 = 1.2 atm

This calculation shows that the partial pressure of oxygen at this depth using EAN