What is the formula for calculating the duration of oxygen flow?

The formula for calculating the duration of oxygen flow is based on understanding how long the oxygen in a tank will last given its current pressure, the cylinder constant for the type of tank being used, and the flow rate at which oxygen is being administered.

Choosing the second option is correct because it accounts for the residual pressure in the cylinder. The formula works as follows: you subtract the "safe residual pressure" (usually around 200 PSI) from the total tank pressure to determine the usable pressure. This gives you the effective pressure of oxygen available for flow. Next, multiplying this effective pressure by the cylinder constant (which is a value that reflects how much gas is available per unit pressure for that specific type of tank) and then dividing by the flow rate in liters per minute provides a reliable estimate of how long the tank will last before it runs out of oxygen.

The other choices fail to provide a complete or accurate representation for calculating duration. One suggests using total tank pressure without accounting for the safe residual pressure, which could lead to overestimating available oxygen time. Another misrepresents the relationship entirely by not incorporating tank pressure correctly in relation to flow rate or just using flow rate without any consideration for pressure or tank constant. The remaining choice inaccurately