Page 58 - Journal of Special Operations Medicine - Spring 2017

Effectiveness of Pulse Oximetry Versus Doppler
for Tourniquet Monitoring

Piper Wall, DVM, PhD; Charisse Buising, PhD; Lisa Grulke, BA; Alexander Troester, BS;
Nicholas Bianchina; Shannon White, BS; Rosemarie Freymark, BA; Ali Hassan, BA;
James Hopkins, MD; Catherine Hackett Renner, PhD; Sheryl Sahr, MD

ABSTRACT

Background: Pulse oximeters are common and include be frequently lost or perhaps not initially achieved.
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arterial pulse detection as part of their methodology. Laboratory data show the pressure exerted by extremity
The authors investigated the possible usefulness of pulse tourniquets declines quickly following completed tour-
oximeters for monitoring extremity tourniquet arterial niquet application, which is associated with loss of arte-
occlusion. Methods: Tactical Ratcheting Medical Tour- rial occlusion. 4–7
niquets were tightened to the least Doppler-determined
occluding pressure at mid-thigh or mid-arm locations on The noninvasive, laboratory gold standard for pulse detec-
one limb at a time on all four limbs of 15 volunteers. tion distal to an extremity tourniquet is arguably audible
A randomized block design was used to determine the Doppler ultrasound. Doppler ultrasound pulse detection
placement locations of three pulse oximeter sensors on depends on maintenance of correct sensor positioning
the relevant digits. The times and pressures of pulsatile and limitation of background noise: both challenging
signal absences and returns were recorded for 200 sec- in a prehospital environment. An alternate noninvasive
onds, with the tourniquet being tightened only when the method of distal pulse detection is pulse oximetry. Pulse
Doppler ultrasound and all three pulse oximeters had oximetry sensors for use on digits are designed to remain
pulsatile signals present (pulsatile waveform traces for the in place without operator assistance, do not require pre-
pulse oximeters). Results: From the first Doppler signal cise positioning over an artery, and are not affected by
absence to tourniquet release, toe-located pulse oximeters noise. However, pulse oximetry is affected by motion and
missed Doppler signal presence 41% to 50% of the times can be affected by ambient light. Additionally, the designs
(discrete 1-second intervals) and missed 39% to 49% of of current clinical use pulse oximeters are optimized for
the pressure points (discrete 1mmHg intervals); finger- display of accurate arterial oxygen saturation (Spo ), not
2
located pulse oximeters had miss rates of 11% to 15% for indicating the presence of a weak arterial pulse.
of the times and 13% to 19% of the pressure points. On
toes, the pulse oximeter ranges of sensitivity and specific- The study purpose was to compare pulse oximetry pulse
ity for Doppler pulse detection were 71% to 90% and detection with Doppler pulse detection distal to an ex-
44% to 51%, and on fingers, the respective ranges were tremity tourniquet. The hypothesis was that pulse ox-
65% to 77% and 78% to 83%. Conclusion: Use of a imetry pulse detection would not match Doppler pulse
pulse oximeter to monitor limb tourniquet effectiveness detection.
will result in some instances of an undetected weak arte-
rial pulse being present. If a pulse oximeter waveform is Methods
obtained from a location distal to a tourniquet, the tour-
niquet should be tightened. If a pulsatile waveform is not The Drake University Institutional Review Board ap-
detected, vigilance should be maintained. proved this prospective study involving the use of tour-
niquets on the thighs and arms of 15 healthy volunteers.
Keywords: tourniquet; hemorrhage; first aid; emergency The tourniquets were previously requested from and do-
treatment nated by m2 Inc. The pulse oximeters were provided by
®
UnityPoint Health Des Moines, Iowa Methodist Medi-
cal Center.
Introduction
Tourniquets
It is desirable for extremity tourniquets to exert suf ficient Ratcheting Medical Tourniquets (RMTs; m2 Inc,
®
pressure to stop limb arterial blood flow. Military-use www.ratchetingbuckles.com) were used because their
1,2
data indicate tourniquet arterial occlusion may either self- securing, ratchet-based tightening system allows

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