Supplementing oxygen through the oxygen cylinder either to thrive in extreme altitudes (>8,000 meters) to ascent peak or to treat hypoxia related illnesses is a very common practice. This has been in practice since decades. But, every time someone decides to use the oxygen cylinder, s/he faces the most difficult questions;
- How much oxygen is there in the cylinder? And,
- How long will it last?
Cylinder size and total oxygen capacity:
The oxygen capacity of the cylinder depends on the size of the cylinder and here is the common type of cylinder size and its capacity:
| Cylinder size | D | E | F | G | J |
| Oxygen capacity (Liters) | 340 | 680 | 1360 | 3400 | 6800 |
| Water capacity (Liters) | 2.3L | 4.7L | 17L | 39L | 47.2L |
To calculate the oxygen capacity of any type of oxygen cylinder the formula is:
Cylinder Capacity (Liters) = Water capacity × 144
Longevity of the cylinder/Duration of oxygen supply:
This depends on the flow rate, cylinder (tank) pressure, residual pressure and conversion factor of different cylinder size. And, this can be calculated using the following formula:
Time to runout a cylinder = (Cylinder pressure in PSI – 200) × Cylinder conversion factor ÷ Flow rate (Liter/min)
Residual pressure = 200 (constant)
Cylinder pressure = measured in the pressure gauze attached to the cylinder
Flow rate = desired flow rate adjusted in the flow meter
| Cylinder size | Cylinder conversion factor |
| C | 0.085 |
| D | 0.17 |
| E | 0.34 |
| F | 0.68 |
| G | 1.7 |
| J | 3.4 |
Cylinder conversion factor = depends on size of cylinder
Example:
Please calculate the time to rundown the oxygen cylinder (F-size) at given pressure and flow rate:
Gauze pressure = 2,000 psi
Residual pressure = 200 psi
Flow rate = 5 liter/min
Time duration = (2000-200) × 0.68 ÷ 5
= 244.8 minutes or 4.08 hours
Safely used the oxygen delivery devices!
Dr. Santosh Baniya, MD (July, 2022)