Tourniquet Cuff Technology
Tourniquet Cuff Technology: What is the purpose of a tourniquet cuff?
The purpose of a tourniquet cuff is to safely stop or restrict arterial blood flow into a portion of an extremity by applying a uniform circumferential pressure around the extremity at a desired location.
Pneumatic tourniquet cuffs
In general, a pneumatic tourniquet cuff is composed of an inflatable bladder with one or two pneumatic connections (ports), a stiffener, contact closures, and a stabilizer. The inflatable bladder holds pressurized gas provided by a tourniquet instrument and exerts pressure around the extremity. The pneumatic port(s) deliver the compressed air from the tourniquet instrument to the cuff bladder through the pneumatic tubing. The stiffener helps direct the pressure exerted by the bladder inward toward the extremity, and helps maintain the cuff in a stable position on the limb when inflated. Hook and loop contact closures are typically used to fasten the tourniquet cuff around the extremity. Some cuffs utilize hook and loop contact closures with pull tabs on the hook component to facilitate easier and faster cuff removal. The stabilizer is used to assist cuff application and helps prevent the cuff from shifting on the limb during use.
In the United States, pneumatic tourniquet cuffs are regulated as Class I medical device by the Food and Drug Administration (FDA). Risks of injuries to patients and legal liability for users arise from use of a pneumatic tourniquet cuff not meeting the FDA requirements. Therefore, it is important to only use pneumatic tourniquet cuffs that meet all relevant FDA requirements. Click here to learn more about FDA requirements for pneumatic tourniquets in the United States.
Personalized tourniquet cuffs
Personalized tourniquet cuffs are state-of-the-art tourniquet cuffs that are designed to better match patient limb shape and size, and thus provide more efficient application of cuff pressure to the limb, allowing lower and safer tourniquet pressures to be used [1]. Personalized cuffs better match patient limb shapes through a variable-contour design that allows the user to adapt the shape of the tourniquet cuff to a wide range of non-cylindrical (i.e. conical) limb shapes. They also better match patient limb sizes through pediatric, adult and bariatric cuff designs.
In order to select the correct personalized tourniquet cuff it is important to understand the key properties of a tourniquet cuff. This includes the cuff shape, size, number of bladders and ports, reusability and stabilizer.
In addition, personalized tourniquet cuffs are accompanied by matching limb protection sleeves that are used to minimize skin pinching and bruising. Click here to learn more about matching limb protection sleeves.
Cuff shape
Tourniquet cuffs can be cylindrical or contour in shape. Cylindrical tourniquet cuffs are designed to fit optimally on cylindrically shaped limbs. However, human limbs may be conically-shaped (i.e. tapered), particularly in extremely muscular or obese individuals. Applying a cylindrical cuff on a tapered limb can result in poor fit, sliding of the cuff distally on the limb during the procedure, and inability to achieve a bloodless field at normal pressures. Figure 1 demonstrates the poor fit caused by applying a cylindrical cuff to a tapered limb.
Figure 1: Cylindrical cuff applied to a tapered limb. Note: large distal gap.
Contour cuffs have an arc-shaped design that, when wrapped around a limb, gives them a smaller diameter distally than proximally. Contour cuffs enhance comfort in patients with tapered limbs and reduce the risk of mechanical shearing. It has been reported that contour tourniquet cuffs occlude blood flow at lower inflation pressures than standard rectangular cuffs of equal width, which may be attributable to better cuff fit and more efficient transmission of pressure to deep tissues [2]. There are two types of contour cuff designs; fixed-contour and variable-contour.
Fixed-contour cuffs are designed to optimally fit one specific limb shape. Applying a fixed-contour cuff on a limb with a different shape will result in a distal gap. Fixed-contour cuffs cannot be adjusted to fit a wide range of limb shapes. Variable-contour cuffs are better for non-cylindrical limb shapes, as explained below.
Figure 2 Pivoting fastening straps on a variable-contour cuff.
Variable-contour cuffs are contour cuffs that can be adjusted to the shape of the limb. They have pivoting fastening straps that allow the proximal and distal circumferences to be adjusted, allowing the cuff to conform to a variety of limb shapes, and thus be personalized to each patient, as shown in Figure 2. Variable-contour cuffs enhance comfort in patients with tapered limbs, decrease the risk of mechanical shearing, and can occlude blood flow at lower pressures due to the improved fit to the limb. Notice there is no distal gap when a personalized cuff is applied to a tapered limb (Figure 3) compared to the large distal gap when a cylindrical cuff is applied to a tapered limb (Figure 1).
Figure 3: Variable-contour cuff applied to a tapered limb. Note: personalized fit and elimination of the distal gap.
Cuff size
Tourniquet cuffs come in a variety of sizes. Different cuff sizes are used on the upper arms, forearms, thighs, and lower legs. Cuff size is also specific to the patient population, with different sizes used for pediatric, adult, and bariatric patients, as shown in Figure 4 and Figure 5.
Some manufacturers color-code their cuffs to assist the user in selecting the most appropriate cuff for the patient. The perioperative staff should follow the manufacturer’s guidelines to determine the correct cuff size.
Figure 4: Pediatric cuffs with matching limb protection sleeves.
Figure 5: (top to bottom) 52” and 44” bariatric cuffs, 34”, 24”, and 18” adult cuffs.
Cuff length
The length of the cuff is determined by the size of the limb. A cuff that is not appropriately sized for the limb (i.e. too long or too short) can cause problems.
Selecting a cuff that is too long, resulting in excessive overlap, may be difficult to apply snugly and may be less stable (causing the cuff to move distally or shift on the patient’s limb). These problems may prevent occlusion of arterial blood flow at normal cuff pressures, lead to loss of occlusion during the procedure, and lead to skin injury.
Selecting a cuff that is too short, resulting in too little overlap of the inflatable bladder portion of the cuff, produces uneven distribution of pressure and can lead to loosening of the cuff or an inability to sustain occlusion.
To determine the appropriate cuff length, measure the circumference of the limb near the middle of the location chosen for the cuff and refer to the cuff manufacturer’s instructions for the appropriate cuff size.
In general, the shortest cuff giving at least the manufacturer’s specified minimum overlap should be used. Some advanced cuffs have a secondary fastener on the inside surface near the strap end of the cuff to assist with cuff application and to increase cuff stability, as shown in Figure 6. If this patch does not fully engage the loop fastener on the outside of the cuff, overlap is insufficient and a longer cuff must be selected.
Some cuffs incorporate an engagement shield on the outer surface of the cuff to make cuff application easier and faster by preventing the contact closures from engaging prematurely (Figure 7).
Figure 6: Additional hook-type fastener patch on the inside surface of some advanced tourniquet cuffs.
Figure 7: Engagement shield on the outside surface of some advanced tourniquet cuffs.
Cuff width
It has been shown that a cuff with a wider bladder occludes blood flow at a lower pressure level than a cuff with a narrower bladder [2, 3, 4]. This may be related to more efficient pressure transmission to the deeper tissues with a wider cuff. Lower pressures, and associated lower pressure gradients, may reduce the risk of pressure-related injuries to the patient [5, 6]. Furthermore, Estebe et. al [7] demonstrated that a wide tourniquet cuff is less painful than a narrow cuff if inflated at lower pressures and at these lower pressures it is still effective at occluding blood flow.
Extra care must be taken with unusually small adult patients and pediatric patients to ensure that the correct cuff width is used and that the cuff edges do not lie close to the joints of the limb to reduce the risk of nerve injury. Click here to find out how wider cuffs reduce tourniquet pressures and pressure gradients, and increase patient safety.
Number of bladders and ports
Most tourniquet cuffs contain a single pneumatic bladder. However, cuffs designed for Intravenous Regional Anesthesia (IVRA) have two bladders side by side inside a single tourniquet cuff. These dual-bladder cuffs allow the inflation and deflation of each bladder to be controlled independently, which allows anesthesia professionals to control patient pain, thereby increasing patient comfort. Click here to find out more about Intravenous Regional Anesthesia.
Cuff bladders can have either one port connector (single-port) or two port connectors (dual-port). A single-port bladder is used with a single-port tourniquet instrument; the same port is used for both pressure sensing and pressure control. A dual-port bladder is used with a dual-port tourniquet instrument; one port is used for pressure sensing and the other port for pressure control. Each port is connected to the instrument via a pneumatic tubing.
Care must be taken such that the proper cuff is selected for the specific patient and surgery. Figure 8 shows examples of tourniquet cuffs with different combination of port connectors and bladders. The perioperative staff should follow the manufacturer’s guideline for proper cuff selection. Click here to learn more about Tourniquet Cuff Selection.
Figure 8: (A) Single-port, single-bladder cuff; (B) dual-port, single-bladder cuff; (C) single-port, dual-bladder cuff; and (D) dual-port, dual-bladder cuff.
Offset port connectors
Some advanced tourniquet cuffs have an offset port design that facilitates cuff application and improve patient safety (Figure 9). In some cuffs with an offset port design, the ports and tubing can be positioned in the desired location prior to securing the cuff around the limb. By positioning the cuff port connectors on or near the lateral aspect of the limb, the perioperative staff can avoid pressure on the nerves, kinking of the tubing, and pneumatic occlusion at the port connections. Some cuffs with an offset port design have extended port tubes to ensure the pneumatic tubings are clear of the surgical site (Figure 9).
Figure 9: Cuff designs with offset ports (top and middle), and cuff design without offset ports (bottom). Cuff design with extended port tubes (middle).
Pneumatic tubing
Pneumatic tubing provides a pneumatic passageway between the tourniquet cuff and the tourniquet instrument. It allows the tourniquet instrument to inflate, deflate and regulate the cuff, as well as to monitor the pressure in the cuff. Depending on the type of cuff used, there may be one or two sets of pneumatic tubing per bladder. Most pneumatic tubing sets are color-coded to assist the surgical staff in identifying the correct tourniquet during the surgery. Modern tourniquet systems typically use positive-locking connectors which are safer because they are less likely to disconnect accidentally during use, in contrast to Luer-lock connectors used on some older tourniquet systems.
Figure 10: Positive-locking connectors with color-coded pneumatic tubing.
Cuff reusability
Reusable and single use tourniquet cuffs are available.
Sterile, disposable cuffs are available for situations that require placement of a sterile tourniquet near the operative site, or for use in contaminated surgical cases [8]. The design and materials of disposable cuffs are suitable for a single sterilization cycle and single use only and must not be re-sterilized or reused. If a disposable cuff is selected, it must be discarded at the end of the procedure.
Reusable cuffs are not designed to be sterilized and must be used with sufficient sterile draping to isolate the cuff from the sterile field. Reusable cuffs are intended to be used multiple times and cleaned following proper procedures between each use.
The perioperative staff should follow the cuff manufacturer’s instructions and their facilities’ procedures for cuff cleaning and reuse. Click here to learn more about cuff maintenance, cleaning and reprocessing.
Cuff stabilizer
Proper application of the pneumatic tourniquet cuff is critical to minimize the risk of patient injury [8, 9]. A loose fitting cuff may shift after placement, which causes frictional burn to the patient’s skin [9]. In addition, higher pressures may be needed if the cuff is applied too loosely.
The cuff stabilizer is used to assist snug cuff application and to prevent the cuff from shifting during use. Cuff shifting can interfere with the surgical site and may result in loss of arterial occlusion. Generally, tie ribbons are used as the stabilizer, as shown in Figure 11. However, some newer cuffs use releasable application handles as the stabilizer, as shown in Figure 12. Releasable application handles allow more consistent cuff application, faster cuff removal, and maintain the cuff in a stable position on the limb during use. Click here to learn more about Tourniquet Cuff Application.
Figure 11: Tourniquet Cuff with a Tie Ribbon Stabilizer
Figure 12: Tourniquet Cuff with a Releasable Application Handle Stabilizer.
Matching limb protection sleeves
Matching limb protection sleeves are matched to the personalized tourniquet cuff to help protect the soft tissues underneath the cuff by reducing wrinkling, pinching, and mechanical shearing of the tissue. These sleeves are formed from elastic, low-lint, and soft material designed and sized to give optimal protection to limbs within the recommended size range of the matching cuff. Some tourniquet cuff manufacturers color code their matching limb protection sleeves to help ensure that the correct sleeve is used with the selected cuff. As this color coding is specific to each manufacturer, tourniquet cuffs and sleeves from different manufacturers should never be mixed.
Figure 13: Matching limb protection sleeves.
In terms of safety and effectiveness, a sleeve that is not specifically matched to the cuff being used may not optimally protect the underlying tissues, may impair the performance of the cuff, and may interfere with venous blood flow when the cuff is deflated, as explained below. In addition, materials that may shed loose fibers, such as cotton cast padding or sheet padding, should be avoided, as lint from these materials can become embedded in the fasteners and reduce the effectiveness, potentially leading to an unexpected release of the cuff from the limb during the procedure.
Evaluation of different limb protections in literature
Tredwell et al. [10] conducted a quantitative analysis of wrinkling and pinching of the skin in a cuff-limb interface study in children. In a total of 44 trials on the upper arms and thighs of two healthy child volunteers, one type of pediatric cuff with a matching limb-protection sleeve designed and recommended by the manufacturer produced significantly fewer, and less severe pinches and wrinkles in the skin surface than a second type of tourniquet cuff with or without two layers of commonly available cast padding, and a third type with padding. With the second type of cuff, using cast padding reduced skin wrinkling compared to applying the same cuff on unprotected skin.
Based on a total of 55 trials of five different limb protection types on the upper arms and thighs of five adults, stretched sleeves made of two-layer tubular elastic material and matched to specific tourniquet cuffs produced significantly fewer and less severe pinches and wrinkles in the skin surface than all other padding types tested [11]. With cast padding and no limb protection, the most severe wrinkling and pinching usually occurred at the cuff overlap. The matching sleeve was designed to stretch a controlled amount when applied to the limb, applying light compression and in effect “artificially” improve the tone of the skin under the cuff and make the skin resistant to being fathered up into a pinch by the cuff, particularly at the cuff overlap. Using a molding and digital measurement technique, the maximum wrinkle heights and the sums of all wrinkle heights in the skin surface under four different cuff and padding configurations were measured.
Olivecrona, et al. [12] conducted a randomized study to confirm that padding under a pneumatic tourniquet cuff protected against the development of blisters during total knee arthroplasty. The study included 92 patients who were divided into three groups. In group one the limb was protected by a two-layer elastic stockinette (n=33). In group two the limb was protected by cast padding (n=29) and in group three no protective material was used (n=30). The tourniquet used for all patients was a 140-mm-wide contoured cuff or a 100 mm-wide cylindrical cuff. Cuff pressure was determined by the surgeon but 70-100 mm Hg above the patients’ blood pressure was recommended for the contoured cuff. For the cylindrical cuff 100-150 mm Hg above the systolic pressure was recommended. Findings indicated that the two groups with skin protection had fewer skin injuries and no patient with the stockinette had blisters. A total of 10 blisters occurred in the 92 patients. Seven were in patients with no protection and three in patients with cast-padding.
Figure 14 shows a comparison of molds taken under a typical tourniquet cuff with no underlying limb protection, with only cast padding used as limb protection, and with a limb protection sleeve specifically matched to the tourniquet cuff being used.
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| Figure 14. Comparison of molds taken under a typical cuff with: a) no limb protection sleeves b) cast padding c) a limb protection sleeve matched to the cuff being used. | ||
These studies provide evidence that limb protection sleeves improve safety by protecting the skin underlying tourniquet cuffs during tourniquet use, and further provide evidence that greatest safety is achieved through the use of matching limb protection sleeves, designed as described in an above section.
Non-pneumatic tourniquet cuffs
The use of non-pneumatic tourniquets in surgery is very limited due to concerns related to safety and effectiveness. Historically, the use of a surgical glove as a wrist tourniquet for hand surgery has been reported, as has the use of a Penrose drain for digit surgery. However, in surgery today, non-inflatable tourniquets have been supplanted by the safer, more effective and more convenient use of modern electronic tourniquet systems that include pneumatic tourniquet cuffs. For phlebotomy or intravenous infusion, simple rubber tubing may be utilized to stop venous flow temporarily. For prehospital care of a patient with trauma to an extremity, a non-pneumatic tourniquet may be employed if required by special circumstances to control hemorrhage. However, for many prehospital applications, specialized pneumatic tourniquets are available and incorporate many of the safety features of surgical-grade systems [5, 13].