c. Prepare the Equipment for Administering Oxygen. Ensure that the
humidifier is filled to the proper level. (If the humidifier is too full, the bubbling water will
overflow into the gauges.) Attach the humidifier to the flow meter and attach the
connecting tube from the nasal cannula or face mask to the humidifier (paragraphs 3-5
and 3-6). Set the flow rate at two liters per minute. Feel to determine if the oxygen is
flowing through the nasal tips of the cannula.
d. Calculate the Duration of Flow. The duration of flow is the estimated
amount of time that a given cylinder of oxygen will supply oxygen at a given rate. A
safety factor (the safe residual) is built into the formula.
(1) Determine the pressure of the oxygen in the cylinder from the pressure
gauge on the cylinder.
(2) Determine the safe residual level. The safe residual established by the
American Academy of Orthopedic Surgeons is 200 p.s.i. Your SOP, however, may
establish a different safe residual.
(3) Determine the available cylinder pressure by subtracting the safe
residual from the cylinder pressure. For example, a cylinder with a pressure of 2000
p.s.i. has an available pressure of 1800 p.s.i. if the safe residual level is 200 p.s.i.
(2000 - 200 = 1800 p.s.i. available pressure.)
(4) Determine the conversion factor. Each type of oxygen cylinder employs
a conversion factor based upon its size. For example, the "D" cylinder authorized for
use in battalion aid stations has a conversion factor of 0.16. The conversion factors are:
(a) "D" = 0.16
(b) "E" = 0.28
"G" = 2.41
(d) "H" & "K" = 3.14
(e) "M" = 1.56
(5) Determine the available liters by multiplying the available pressure by
the conversion factor. For example, a "D" oxygen cylinder with an available cylinder
pressure of 1800 p.s.i. has 288 litters of available oxygen (1800 x 0.16 = 288).
Remember that the available liters do not include the oxygen that is still left in the
cylinder when the safe residual level is reached.
(6) Determine the flow rate. The flow rate is prescribed by the physician
and expressed as liters per minute (lpm or l/m).