Page 79 - JSOM Summer 2020

challenges to range from ideal to worst. The design included TABLE 1 Step Names With Notes on Step Details
a test of five speeds in tourniquet use from fastest to slowest Step Name Notes, Including Key Bundled Actions
in five strata simulating minimal to maximal time challenges, See, locate, and recognize the bleeding
respectively. Time challenges for the four nonminimum strata Detect bleed wound
could include various issues like a user struggling in a step, Judge bleeding severity, rate, amount, and
making an error, and undoing a step then redoing it correctly. Assess nature
Problems tend to beget more problems, which may compound Make decision about intervening in this
into clusters, which may yield maximum times. Decide situation
Get and unlock phone, dial, and reach
Call 9-1-1
The situation was routine first aid and not care under threat, dispatcher
such as gunfire. The patient had one wound. The caregiver was Talk with dispatcher Discuss the emergency
uninjured, undistracted, at arm’s length to the patient, and had End call Close application and put phone away
at hand a tourniquet, a pair of medical gloves, a smartphone, Find tourniquet Locate and grasp a tourniquet
and a marker. The need for tourniquet use was a clinical in- Unwrap the tourniquet from its plastic
dication defined by an externally visible blood loss of 177mL, Unwrap tourniquet wrapper
a threshold used previously as a referent amount in bleeding Table tourniquet Put the tourniquet down
control. The indication is patient determined whereas its de- Get gloves Find and grasp two medical gloves
11
tection is user determined; in self-aid, the patient is the user. Don gloves Put on the pair of gloves
Grab tourniquet Pick the tourniquet back up
The task of tourniquet use was divided into steps in a set or-
der (Table 1). The task was deconstructed by breaking down Apply tourniquet Loop onto limb in place, pull slack, and
the procedure of tourniquet use in first aid into its essential turn rod
components as discrete psychomotor performance units. The Secure Clip rod, tidy band, secure strap, and
12
write time
order of the 14 steps was routine as experienced in simulation,
teaching, and caregiving. The early steps were helping behav-
iors and late steps were initial care for an injury. The first step has routinely simulated at 10.4mL/s in combat with a thigh
was detecting a hemorrhage. The second step included assess- amputation injury. 10,11,25 That thigh amputation is an un-
ing the bleeding. The third was deciding to intervene. The common trauma that is a severe threat to life, whereas the
fourth was initiating an emergency call by phoning 9-1-1, a US Navy, on occasion, has simulated a rare trauma that is a
step that bundled finding and unlocking a phone, turning air- critical threat to life at a hemorrhage rate of 25mL/s when the
plane mode off, opening a telephone application, dialing 9-1-1, student is to learn about combat-like stress. 26
and reaching a dispatcher. The fifth step included talking with
the dispatcher. The sixth ended the call. The seventh through Step metrics included durations and blood losses. For those
10th steps were finding a tourniquet, unwrapping it, putting steps with uncontrolled bleeding, loss data were calculated as
it down, and getting two gloves, respectively. The 11th, 12th, the bleeding rate multiplied by the duration of bleeding. For
and 13th steps were donning the gloves, picking the tourni- the final step, when bleeding was controlled, the bleeding rate
quet back up, and applying the tourniquet, respectively. The was 0mL/s and blood loss was 0mL. For the 13th step of tour-
tourniquet application bundled placing the tourniquet on the niquet application, the tightening tourniquet incrementally
limb, routing the band, removing slack from the band, and controlled bleeding from 2.5mL/s to 0mL/s; we split the differ-
turning the rod to stop the bleeding. By definition, tourniquet ence to approximate slowed bleeding at 1.25mL/s. Because we
application ended at a key physiologic moment when bleeding set a bleeding rate for each step, the proportions of times for
was controlled, whereas that step began when the tourniquet individual steps were to be identical among all strata. Blood
first touched the patient. The 14th and final step was called loss proportions were similarly identical among strata, but the
“secure,” which meant the time after bleeding was controlled. time-blood proportions differed by step, due to differences in
Secure bundled clipping the rod, tidying the band under the blood loss rates. A trial was the tourniquet use for a given
clips, securing the strap to bridge between the clips, and writ- stratum. There were five trials. Trial duration was the sum of
ing the application’s time of day with a marker on the strap. its steps. A trial blood-loss volume was similarly summed from
its 14 steps as formulated in Equation 1:
The data on each step had a duration in seconds. Each step’s
time was estimated as a minimum. The lead author estimated trial volume = Σ (rate × time) [Equation 1]
the minimum for each of the 14 steps from publications 13–21 or
his experience in caregiving, teaching, and research. 22–24 Each Summation is from step 1 to step 14. Deconstructing the task
of the 14 minimums constituted a base stratum of data to rep- into its component steps preceded the redesigning of the task.
resent a fast tourniquet use. From this base stratum, four other Manipulations of the steps were compared with the original
strata of data were calculated by multiplying the minimums 14 steps in order. Manipulation categories included step dele-
data by four ordinal factors: 2.5, 5, 7.5, and 10. In this way, tions, movements, or their combinations. Movement of a step
durations varied 10-fold. The five strata constituted the data was from its ordered place to another place. The combination
set, and the strata times were named minimum, short, moder- was a deletion with a movement. These manipulations were
ate, long, and maximum. counterfactual to the unmanipulated steps, which served as
a basis of comparison. For example, applying the tourniquet
To globally maximize the pertinence of the mathematical before gloves are donned may stop the hemorrhage quickly,
model, we simulated a common emergency that was a seri- whereas donning gloves after bleeding is controlled would
ous threat to life. An uncontrolled bleeding rate was set at mitigate the risk of pathogen transmission when a wound is
2.5mL/s. This rate is about one-fourth of what our laboratory dressed or a limb is handled.

Step Duration in Tourniquet Use | 77