Page 62 - Journal of Special Operations Medicine - Spring 2017

Excluded Data Table 2 Changes in Pulse Status as Indicated by Doppler
Pressure data from arms small enough to require the Signal
Pediatric RMT were excluded. Time and pressure data Extremity
from one arm application were excluded following the Doppler Signal Thigh Arm
first Signal Gones because no Doppler Signal Return
occurred on tourniquet release, indicating a change in First
Doppler sensor position had occurred. Time and pres- Gones 30 30
sure data from one arm and two thigh applications were Returns
excluded following the second Signal Gones because no Prerelease 29 19
Doppler Signal Returns occurred on tourniquet release,
indicating a change in Doppler sensor position had Postrelease 1 10*
occurred. Second
Gones 15 14
Signal Time and Pressure Comparisons Returns
As can be seen in Figure 1, the first Signal Gones of the
pulse oximeters were generally close in time and pres- Prerelease 4 3
sure to the first Signal Gone of the Doppler. This was Postrelease 10 † 9 ‡
generally true of any Signal Gones that resulted from a Third
tightening of the tourniquet; in Figure 1, see the abrupt, Gones NA 1
discrete pressure increase at 162 seconds and tight
grouping of second Signal Gones for Doppler and each Returns
pulse oximeter. Signal Returns had much more variable Prerelease NA 0
spacing, especially those Signal Returns that occurred Postrelease NA 1
prior to release of the tourniquet; see the ratchet release Gones, no audible distal arterial Doppler pulse signal present with the
pressure drop at 209 seconds in Figure 1. ratcheting buckle in its rest position and the applier’s hands off the
tourniquet; Returns, audible distal arterial Doppler pulse signal pres-
As indicated in Table 2, all tourniquet applications ent after being gone; Prerelease, before tourniquet release; Postrelease,
after tourniquet release; NA, not applicable.
achieved a first Doppler Signal Gone. Of the 60 first *One first Doppler Signal Gone on the arm did not have a Doppler
Doppler Signal Gones, seven thigh and two arm Dop- Signal Return.
One second Doppler Signal Gone on the thigh did not have a Doppler
pler Signal Gones were preceded by a pulse oximeter † Signal Return.
Signal Gone on the immediately preceding ratcheting ‡ Two second Doppler Signal Gones on the arm did not have Doppler
buckle single ladder tooth advance. One thigh, first Signal Returns.
Doppler Signal Gone was preceded by a pulse oximeter
Signal Gone two ladder teeth prior, during the ratchet- release Doppler Signal Returns, two thigh Doppler Sig-
ing buckle advance. nal Returns were preceded by a pulse oximeter Signal
Return. The time and pressure differences of those two
The strategy of limiting the initial advance of the ratch- pulse oximeter Signal Returns from their trailing Dop-
eting buckle to the least number of ladder teeth needed to pler Signal Returns were 88 seconds, 9mmHg and 59
achieve Doppler Signal Gone succeeded in providing one seconds, 5mmHg.
or more pre–tourniquet release Doppler Signal Returns
with almost every thigh tourniquet application and most The post–tourniquet release Signal Returns occurred in
arm tourniquet applications. The times and pressures of response to a large pressure decrease in a very short in-
the Signal Gones within any single tourniquet applica- terval, so a few seconds of difference in Signal Return
tion were generally closely clustered because most Sig- times corresponded to large differences in Signal Re-
nal Gones occurred in response to the same ratcheting turn pressures. Post–tourniquet release Signal Returns
buckle advance on the ladder (Figure 2A, 2B). Doppler probably have little clinical relevance for field monitor-
Signal Gones occurred at slightly higher pressures than ing of the adequacy of tourniquet tightness and are not
did pulse oximeter Signal Gones (p = .011). graphically shown. The differing times for the pulse ox-
imeters to show a pulsatile waveform post–tourniquet
The pre–tourniquet release Signal Returns were gener- release do, however, have clinical relevance as indica-
ally spread out in time and, to a lesser extent, in pressure; tors of pulse oximeter internal signal-processing effects
they occurred as pressure declined under the tourniquet on when and if a pulsatile waveform is displayed. After
(Figure 2C, 2D). Signal Returns had to occur with all tourniquet release, the delay before post–tourniquet re-
four monitoring devices before an advance of the ratch- lease, pulse oximeter Signal Returns ranged from 1 to
eting buckle would take place. Of the 55 pre–tourniquet 31 seconds.

40 Journal of Special Operations Medicine Volume 17, Edition 1/Spring 2017