In the event of an interrupted main pipeline gas delivery, which factor determines how long an O2 tank at 1000 psi will last at a flow of 2L/min?

The longevity of an O2 tank at a specific pressure and flow rate is determined by both the tank's pressure and the flow rate. The tank pressure indicates the amount of oxygen available in the tank, while the flow rate determines how quickly oxygen is consumed.

To understand this, consider that the total volume of gas available in the tank is proportional to its pressure (measured in psi) and the tank's capacity (for instance, an E cylinder has a defined volume). When oxygen is delivered at a flow rate, the amount of time the tank will last can be calculated by dividing the total volume of oxygen in the tank (derived from pressure) by the volume being used per minute (the flow rate). Therefore, the interplay between how much pressure is contained in the tank and the rate at which oxygen is utilized directly impacts the duration for which the O2 tank will last.

Other options do not directly relate to the calculation of how long the tank will last. The size of the E cylinder is static and does not change during use; the duration of the surgical procedure influences the need for oxygen but doesn't determine how long the tank lasts at a given flow rate; and while ambient temperature can affect gas density, it is not a direct factor in calculating