Untangling Misconceptions about Narrow Cuffs and Safety

It has been well established in medical literature that the probability of tourniquet-related injuries increases as tourniquet pressure increases, and as the pressure gradient near the edges of tourniquet cuffs increase, e.g. [1-7]. Unnecessarily high tourniquet pressure gradients represent a serious and recognized hazard associated with unnecessarily high probabilities of patient injuries, specifically nerve injuries. Hazardously high pressure gradients can be minimized by the design of improved pneumatic tourniquet cuffs and by the design of improved pneumatic tourniquet instruments.

Over the last few decades, the safety and effectiveness of surgical tourniquets have increased greatly as a result of clinical studies, peer-reviewed publications, and innovations in both the tourniquet instrument and the tourniquet cuff. Some of the major advances that resulted in increased safety and effectiveness are listed below:

1. Microcomputer-based tourniquet instruments allowing more accurate and automatic pressure regulation and control, and many important safety features not possible in early pneumatic tourniquet systems [7, 8].
2. Tourniquet instruments with the capability to recommend a safe and effective tourniquet pressure based on the patient’s Limb Occlusion Pressure (LOP). LOP can be defined as the minimum pressure required, at a specific time in a specific tourniquet cuff applied to a specific patient’s limb at a specific location, to stop the flow of arterial blood into the limb distal to the cuff.   The use of LOP to set tourniquet pressure for individual patients is an important factor that allows tourniquet pressures and pressure gradients to be reduced [8-12].
3. Wider tourniquet cuffs that have been shown to reduce the pressures required to stop arterial blood flow [11, 13, 14].
4. Variable-contour tourniquet cuffs that can be adjusted to the shape of the limb, providing personalized fit, and resulting in lower pressure and pressure gradients [11, 13, 14].
5. Limb protection sleeves matched to the tourniquet cuffs help protect the soft tissues underneath the cuffs by reducing wrinkling, pinching, and mechanical shearing of the tissues [14-16].

Even though hazards of high pressures and high pressure gradients are well established in the surgical realm and supported by decades of clinical studies, they are often not well-understood in developing fields.

In recent years, there has been a new and exciting development in improving rehabilitation of injured patients through of use of Blood Flow Restriction (BFR). BFR rehabilitation involves low-load exercise while restricting arterial inflow into the muscle, and occluding venous return from the muscle [17]. Typically, a person needs to lift weights at around 70% of their one repetition maximum (1RM) to have noticeable increase in muscular strength and size [18]. However, heavy resistance training has risk of injuries and may not be used for many at risk population such as the elderly, and patients undergoing rehabilitation. Studies have shown that BFR training at low resistance (20%-30% of 1RM) can increase both muscle mass and strength, and is beneficial for the recovery of injured athletes and patients requiring muscle gain [18-21].

Although BFR has been shown to be successful in the rehabilitation of injured patients, many people in this field do not understand or follow the results from decades of literature on surgical tourniquet safety and effectiveness. As a result, inconsistencies in methodology and equipment have made it difficult to apply a safe and consistent BFR stimulus to patients, preventing a controlled comparison of different BFR protocols, and thus limiting the identification and delivery of optimal patient outcomes. The following is a list of common misconceptions in BFR rehabilitation:

Misconception 1: Setting BFR pressure as a function of blood pressure or at a fixed pressure is safe and effective

Limb Occlusion Pressure (LOP) is the minimum pressure required, at a specific time in a specific tourniquet cuff applied to a specific patient’s limb at a specific location, to stop the flow of arterial blood into the limb distal to the cuff. Loenneke et al. [22,23] demonstrated that setting BFR pressure as a function of blood pressure or at a fixed pressure does not provide a consistent stimulus across patients because these methods of setting pressure neglect important factors that affect LOP, including limb circumference and cuff width, Figure 1. This confirms what has been well established in the surgical tourniquet literature on LOP [7]. Fatela et al. [24] analyzed the effect of relative BFR pressure on the acute neuromuscular response to BFR resistance exercise and showed that muscular activation and neuromuscular fatigue varies as a function of relative blood flow restriction. Consequently, Fatela et al. [24] concluded that it is crucial to determine individual levels of vascular restriction, by quantifying the resting LOP, before engaging in BFR exercise and rehabilitation.

Summary: A restriction pressure level set for each individual patient, based on a percentage of LOP measured at rest, is crucial before engaging in BFR exercise and rehabilitation. Setting BFR pressure as a function of blood pressure or at a fixed pressure will not apply a safe and consistent BFR stimulus to patients. It may result in full occlusion on some patients, and lack of arterial restriction for others.

Misconception 2: Setting pressures based on pain level or intensity level is safe and effective

Some BFR systems recommend setting “individualized” BFR pressures based on the patient’s pain level or intensity level. Typically, they recommend tightening a non-pneumatic belt or increasing pressure in a pneumatic bladder applied to a limb until a 7/10 pain level or intensity level is felt. While this allows some input from the patient in determining the BFR level, this method is highly subjective and will not provide a controlled and consistent BFR stimulus to the patient.

Summary: A restriction pressure level set for each individual patient, based on a percentage of LOP measured at rest, is crucial before engaging in BFR exercise and rehabilitation. Setting BFR pressure based on subjective pain level or intensity level will not apply a safe and consistent BFR stimulus to patients. It may result in full occlusion on some patients, and lack of arterial restriction for others.

Misconception 3: Narrow, non-pneumatic belts and narrow, pneumatic tourniquets are safe

Many BFR devices in the market utilize narrow, non-pneumatic belts or narrow, pneumatic tourniquets to provide BFR stimulus. Most of these devices recommend setting BFR pressures as a function of the patient’s systolic blood pressure, at fixed pressures or based on the patient’s pain level or intensity level which will not apply a safe and consistent BFR stimulus to patients (see misconception 1 and misconception 2). Some devices recommend setting BFR pressures based on LOP which is safer and more effective. However, it has been shown in literature that narrow tourniquet widths result in higher LOPs. Therefore, inherently, narrow non-pneumatic belts and narrow pneumatic tourniquets require and apply higher pressures and pressure gradients resulting in greater risk of patient injury, see Figure 1 [1-7,16].

Summary: Narrow, non-pneumatic belts and narrow, pneumatic tourniquets require higher pressures and higher pressure gradients than wide tourniquets to achieve the same level of BFR stimulus. It has been shown in literature that higher pressures and pressure gradients increase the risk of patient injury. Therefore, use should select and apply a wide tourniquet cuff to reduce the risk of patient injury.

Misconception 4: Blood pressure cuffs are as safe and effective as tourniquet cuffs when used for BFR rehabilitation

Some BFR devices use blood pressure (BP) cuffs to restrict arterial blood flow for BFR rehabilitation. However, BP cuffs do not have inflatable bladders that fully surround the limb, resulting in (1) non-uniform applied pressure, (2) high pressure gradients between the inflatable and non-inflatable regions, and (3) higher risk of tissue displacement and injury under the blood pressure cuff when pressurized at a high level for a sustained period of time. This is because BP cuffs are designed to momentarily restrict and occlude blood flow (1-2 minutes). BP cuffs are not designed to provide sustained pressures. For optimal safety and effectiveness, users should use surgical-grade tourniquet cuffs as they are designed to apply uniform pressures around the limb circumference for sustained and repeated applications.

Summary: Blood pressure cuffs are designed to measure blood pressure. They are not intended to be used for BFR rehabilitation. BP cuffs do not apply uniform pressure to the limb for sustained and repeated applications, resulting in increased risk of nerve and soft tissue injury to the patient. For optimal safety and effectiveness, users should use surgical-grade tourniquet cuffs as they are designed to apply uniform pressures for sustained and repeated applications.

Misconception 5: The patient is safe as long as a BFR device does not occlude arterial blood flow

Some BFR product manufacturers proudly proclaim their systems are inherently safe because the devices physically cannot occlude arterial blood flow. There are videos circulating on the web showing their BFR system applying pressures as high as 500 mmHg to the subject’s limb without occluding arterial blood flow. While it is true arterial blood flow remained non-occluded, the BFR system allows the application of high pressure (500 mmHg), and high pressure gradient over a small surface area (narrow pneumatic belt) resulting in increased risk of patient injury, specifically nerve injuries.

Summary: Narrow BFR tourniquet cuffs apply high pressures and high pressure gradients which increase the risk of patient injury. For safest and optimal BFR stimulus, (1) use wide, variable contour cuffs that provide a personalized fit to the patient resulting in the lowest LOP and restriction pressures, (2) use a tourniquet system that measures the patient’s personalized BFR pressure, based on LOP.

Misconception 6: Any device that applies pressure to a limb is all that is required for a consistent and safe BFR stimulus

Some BFR devices apply pressures to a limb without a microcomputer-based instrument for pressure regulation. This has a negative impact on the safety and effectiveness of the BFR rehabilitation for the following reasons:

1. As the patient exercises, the cuff pressure will deviate from the original set pressure. Without an instrument to regulate the pressure near the set pressure, the cuff may apply occlusive pressure (arterial and venous occlusion) for the entire or majority of the BFR exercise resulting in decreased safety and effectiveness. Beware of narrow cuffs without pressure regulation. The cuff pressure in these devices can change drastically during exercise due to their smaller bladder volume.
2. Without pressure regulation, the belt or tourniquet cuff may shift on the patient’s limb during use, resulting in inconsistent cuff pressure and BFR stimulus.
3. During exercise, the belt may loosen or the tourniquet cuff may leak, resulting in reduced applied pressure and decreased BFR stimulus. Performing BFR with an instrument that provides pressure regulation allows consistent applied pressure and BFR stimulus.

Summary: In order to provide consistent, safe and effective BFR stimulus to the patient, it is important to use a BFR device with the ability to regulate the cuff pressure. For optimal results, users should look for BFR devices utilizing surgical-grade tourniquet cuffs and instruments. Surgical-grade tourniquet cuffs can minimize the risk of cuff movement during use while surgical-grade tourniquet instruments can maintain cuff pressure near the set pressure during exercise. Both surgical-grade tourniquet cuffs and instruments have gone through regulated quality systems ensuring their effectiveness and function.

Conclusion:

Although BFR has been gaining a lot attention in recent years and is shown to be a promising rehabilitation method, users should be aware of the common misconceptions listed above. For optimal BFR stimulus, it is recommended to use personalized restriction pressure based on a relative percentage of LOP, determined automatically on a rest patient by a surgical-grade tourniquet instrument, and applied safely and consistently by a surgical-grade tourniquet cuff.

The use of such tourniquet instruments and cuffs are based on decades of experience in surgical settings, and assures the safe, accurate, and reliable application of pressure to a patient’s limb [7].  Setting and regulating the pressure as a predetermined percentage of the individualized LOP can help avoid adverse events that may result from inadvertently applying pressures that result in complete arterial occlusion [25].  The application of a consistent level of restriction pressure limits variability in BFR intensity for individual patients, since muscular activation, as well as neuromuscular fatigue, varies as a function of relative BFR intensity [24].  Accurately applying a consistent level of restriction pressure enables the outcomes and results of a full range of BFR studies to be compared on a meaningful basis so that optimal protocols can be identified and applied [26,27].

Sources:

[1] Ochoa J, Fowler TJ, Gilliatt RW. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. Journal of Anatomy. 1972 Dec;113(Pt 3):433.

[2] Ochoa J, Danta G, Fowler TJ, Gilliatt RW. Nature of the nerve lesion caused by a pneumatic tourniquet. Nature. 1971 Sept;233:265-6.

[3] Gilliatt RW, Ochoa J, Rudge P, Neary D. The cause of nerve damage in acute compression. Trans Am Neurol Assoc. 1974;99:71-4.

[4] Shaw JA, Murray DG. The relationship between tourniquet pressure and underlying soft-tissue pressure in the thigh. J Bone Joint Surg Am. 1982 Oct 1;64(8):1148-52.

[5] Graham B, Breault MJ, McEwen JA, McGraw RW. Perineural pressures under the pneumatic tourniquet in the upper extremity. The Journal of Hand Surgery: British & European Volume. 1992 Jun 1;17(3):262-6.

[6] Crenshaw AG, Hargens AR, Gershuni DH, Rydevik B. Wide tourniquet cuffs more effective at lower inflation pressures. Acta orthopaedica Scandinavica. 1988 Jan 1;59(4):447-51.

[7] Noordin S, McEwen JA, Kragh Jr CJ, Eisen A, Masri BA. Surgical tourniquets in orthopaedics. JBJS. 2009 Dec 1;91(12):2958-67.

[8] McEwen JA. Complications of and improvements in pneumatic tourniquets used in surgery. Med Instrum. 1981 Jul;15(4):253-7.

[9] Younger AS, Manzary M, Wing KJ, Stothers K. Automated cuff occlusion pressure effect on quality of operative fields in foot and ankle surgery: a randomized prospective study. Foot & ankle international. 2011 Mar;32(3):239-43.

[10] Reilly CW, McEwen JA, Leveille L, Perdios A, Mulpuri K. Minimizing tourniquet pressure in pediatric anterior cruciate ligament reconstructive surgery: a blinded, prospective randomized controlled trial. Journal of Pediatric Orthopaedics. 2009 Apr 1;29(3):275-80.

[11] Younger AS, McEwen JA, Inkpen K. Wide contoured thigh cuffs and automated limb occlusion measurement allow lower tourniquet pressures. Clinical orthopaedics and related research. 2004 Nov 1;428:286-93.

[12]Tredwell SJ, Wilmink M, Inkpen K, McEwen JA. Pediatric tourniquets: analysis of cuff and limb interface, current practice, and guidelines for use. Journal of Pediatric Orthopaedics. 2001 Sep 1;21(5):671-6.

[13] Pedowitz RA, Gershuni DH, Botte MJ, Kuiper S, Rydevik BL, Hargens AR. The use of lower tourniquet inflation pressures in extremity surgery facilitated by curved and wide tourniquets and an integrated cuff inflation system. Clinical orthopaedics and related research. 1993 Feb 1;287:237-44.

[14] Graham B, Breault MJ, Mcewen JA, Mcgraw RW. Occlusion of arterial flow in the extremities at subsystolic pressures through the use of wide tourniquet cuffs. Clinical orthopaedics and related research. 1993 Jan 1;286:257-61.

[15] Olivecrona C, Tidermark J, Hamberg P, Ponzer S, Cederfjäll C. Skin protection underneath the pneumatic tourniquet during total knee arthroplasty: a randomized controlled trial of 92 patients. Acta orthopaedica. 2006 Jan 1;77(3):519-23.

[16] McEwen JA, Inkpen K. Tourniquet safety: preventing skin injuries. Surgical Technologist. 2002;34(8):6-15.

[17] Loenneke JP, Thiebaud RS, Abe T, Bemben MG. Blood flow restriction pressure recommendations: the hormesis hypothesis. Medical hypotheses. 2014 May 1;82(5):623-6.

[18] Loenneke J, Abe T, Wilson J, Thiebaud R, Fahs C, Rossow L, Bemben M. Blood flow restriction: an evidence based progressive model. Acta Physiologica Hungarica. 2012 Sep 1;99(3):235-50.

[19] Bell, Stephanie. “New method may benefit athletes.” ESPN. ESPN Internet Ventures, 11 Nov 2014. Web. 26 Nov 2014. <http://espn.go.com/nfl/story/_/id/11858977/tourniquet-training-change-way-athletes-recover-injuries>.

[20] Martín‐Hernández J, Marin PJ, Menendez H, Ferrero C, Loenneke JP, Herrero AJ. Muscular adaptations after two different volumes of blood flow‐restricted training. Scandinavian journal of medicine & science in sports. 2013 Mar 1;23(2).

[21] Hylden C, Burns T, Stinner D, Owens J. Blood flow restriction rehabilitation for extremity weakness: a case series. J Spec Oper Med. 2015;15(1):50-6.

[22] Loenneke JP, Wilson JM, Wilson GJ, Pujol TJ, Bemben MG. Potential safety issues with blood flow restriction training. Scandinavian journal of medicine & science in sports. 2011 Aug 1;21(4):510-8.

[23] Loenneke JP, Fahs CA, Rossow LM, Sherk VD, Thiebaud RS, Abe T, Bemben DA, Bemben MG. Effects of cuff width on arterial occlusion: implications for blood flow restricted exercise. European journal of applied physiology. 2012 Aug 1;112(8):2903-12.

[24] Fatela P, Reis JF, Mendonca GV, Avela J, Mil-Homens P. Acute effects of exercise under different levels of blood-flow restriction on muscle activation and fatigue. European journal of applied physiology. 2016 May 1;116(5):985-95.

[25] Jessee MB, Buckner SL, Dankel SJ, Counts BR, Abe T, Loenneke JP. The influence of cuff width, sex, and race on arterial occlusion: implications for blood flow restriction research. Sports Medicine. 2016 Jun 1;46(6):913-21.

[26] McEwen JA, Jeyasurya J, Owens J. How can personalized tourniquet systems accelerate rehabilitation of wounded warriors, professional athletes and orthopaedic patients?. CMBES Proceedings. 2016 Nov 9;39(1).

[27] McEwen JA, Jeyasurya J, Owens J. Why is it crucial to use personalized occlusion pressures in blood flow restriction (BFR) rehabilitation?. CMBES Proceedings. 2017 May.