and sometimes are the only linear measurements recorded (see Table 4.3).
The clock method is another way to measure the SA of wounds. In this method, you imagine the wound as the face of a clock. Select a 12:00 reference position on the wound; this posi- tion is usually toward the patient’s head. Then, take the mea- surement from 12:00 to 6:00 and from 3:00 to 9:00. The four steps of the procedure are as follows:
1. Establish the 12:00 position by choosing an anatomic land- mark that is easy to identify and document it for all follow- ing measurements (e.g., 12:00 toward head).
2. Mark 12:00 with arrow on the skin. Repeat with marks at 6:00, 3:00, and 9:00.
3. Measure from wound edge at 12:00 to wound edge at 6:00 position.
4. Measure from wound edge at 3:00 to wound edge at 9:00 position.
In situations such as severe contractures of the trunk and lower extremities, it may be more convenient and easier to reproduce the measurements if another convenient anatomic landmark is selected as the 12:00 reference point; for example, measurements in the foot may use the heel or toes. In a person whose body is con- tracted in the fetal position, a trochanteric pressure ulcer may be more easily tracked if the 12:00 reference point is toward the knee.
computer-assisted technologies can increase precision, infor- mation about measuring with such equipment has been omit- ted from this chapter because these devices are usually research tools and are not commonly available in clinical practice settings.
wounds are diffi cult to position for accurate measurement.
Once a convenient and comfortable position is found, record the position that works best. This will save time and effort and improve the uniformity of measurements over time.
Example: Coccyx wound—position: right side-lying; heel wound—position: left side-lying.
2. Don gloves and remove wound dressing and packing.
3. Place dressing and packing in disposable infectious waste bag.
4. Clean wound with normal saline and syringe with 18-gauge needle or angiocatheter (see Chapter 17 for wound cleansing procedure).
5. Take measurements with disposable wound measurement ruler.
Both of these measurement methods are acceptable and widely used. It is important to bear in mind two things when using them:
1. The geometric formula for the area of a rectangle (length times width) gives only an approximation of a wound’s SA. In fact, it has been estimated to infl ate the size of the wound by as much as 44% if the wound is irregularly shaped and large.10 2. All wound shapes are irregular, so assume that this measure-
ment will be infl ated.
In short, the goal is not to make a precise measurement, but rather to make consistent measurements that can be used to monitor healing. So choose a method that you are comfortable with and record which method is used. Then, use this method consistently. Exhibit 4.3 lists advantages and disadvantages of the clock method and the greatest length and greatest width method.
Gather Your Supplies
Assemble the supplies needed for wound measurement in advance to improve effi ciency and reduce patient fatigue. If wound measurements are taken frequently, assemble a kit made up of these supplies. Keep it with you in a small plastic carrier. These supplies include
• Pen or pencil
• Disposable, plastic straight-edge ruler with linear measure ruled in centimeters
• Disposable gloves
• Normal saline
• Disposable syringe with 18-gauge needle or angiocatheter (for cleaning)
• Gauze paper, pocket-sized notebook, or wound measurement form to record data (see Exhibit 4.4)
Follow a Step-by-Step Procedure
Before measuring, the wound should be cleaned and exam- ined closely. Look carefully at the edges to determine whether they are distinct so that you can measure from wound edge to wound edge. You may wish to use an assistant to help you posi- tion and comfort the patient, control wound “sagging” (see Step 6), record measurements, or seek additional supplies or assistance. Take the following steps:
1. Position the patient. It is easier for everyone if the patient is comfortable during the procedure. Some patients and some
12
9 Greatest
length by greatest width method
Clock Method 12:00 to 3:00 Perpendicular to each other
3
6 FIGURE 4.2 Two wound measurement methods.
EXHIBIT 4.3
Comparison of Two Wound Measurement Methods Greatest Length by Greatest Width Method
Advantages
● Simple and easy to learn and use
● Most common method
● Reliable Disadvantages
● Diameters change as size and shape change, so different diameters are measured each time
● Wound open area will be larger than in clock method Clock Method
Advantages
● Simple and easy to learn and use
● Tracks same place on the wound over time
● More conservative measure of area Disadvantages
● Requires more steps to perform
● More precision required to line up wound points along the clock “face”
● Less commonly used
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10. Apply fresh dressing.
11. Calculate wound SA.
12. Repeat weekly or more frequently, if indicated.
Measuring Undermining and Tunneling
Measurements of undermining (erosion under the wound edge) and tunneling (a sinus) indicate the extent of wound damage into surrounding deep tissue. Undermining/tunneling is often the consequence of wound debridement: when a body of necrotic tissue is removed, the fascial planes can separate during the probing action. Tunneling can progress to become a sinus tract and a pathway for infection. For this reason, any measurement of undermining and tunneling requires careful, gentle probing to avoid further separation of the fascial planes.
A measurement of extensive tunneling is a red fl ag that indicates the urgent need to contact the physician and report the fi nding.
6. Measure the wound using one of the three methods just described. If measurements are always taken in the same order, the tracking of wound size will be more consistent.
Take the length fi rst and the width second. If the clock method is used, take measurements from 12:00 to 6:00 then from 3:00 to 9:00 for consistency. While measuring, control sagging wounds. Full-thickness wounds with undermining can sag from lack of subcutaneous support and the pull of gravity. Try to keep sagging to a minimum and maintain uniform tension for accurate length and width measurements.
7. Record each measurement as it is taken.
8. Dispose of measurement instrument and gloves in infec- tious waste container.
9. Dispose of syringe with 18-gauge needle in sharps container.
CLINICAL WISDOM
Using a Template to Improve Measurement Accuracy To improve accuracy and better align the measurements, cut a circle from paper folded in half twice and mark the four clock points at the four paper folds. Place the circle over the wound to use as a template or guide, taping it to the periwound skin to keep it from shifting.11 Take all measure- ments with the template in place to uniformly track the same wound locations for SA, undermining, and depth (Fig. 4.3).
FIGURE 4.3 Using a template to improve measurement accuracy.
EXHIBIT 4.4
Calculating Percentage Rate of Change in Wound Size
One interesting way to determine how a wound is progressing is to look at the percentage rate of change. This is also an effective way to measure and predict successful outcomes. Percentage rate of change is a simple statistical calculation that uses the follow- ing formula:
1. Baseline (week 0) wound size (0A or overall 0A size) measurement is used as the original size.
2. Subtract the next wound size 0A or overall 0A size measurement (interim) taken from the baseline.
3. Divide by baseline wound measurement and multiply by 100%.
Formula for computing rate of change in wound open area:
−
Baseline open area (OA) Interim open area (OA)
× 100%
Baseline open area Example: Wound open area (OA) baseline week 0 = 30 cm2
Wound open area (OA) week 1 (interim) = 28 cm2 OA baseline – OA week 1 (interim) = 30 − 28 = 2 Divide the remainder by the baseline OA = 2/30 = 0.066
Multiply 0.066 × 100% = 6.6% = Percentage rate of change
Note: A weekly percentage of change would use the prior week’s size measurement instead of baseline. Wound size often changes signifi cantly from week to week in the early phases of healing, and then the rate slows. Referring to the percentage rate of change on a weekly or biweekly basis is a reliable measure of how the wound is healing.
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FIGURE 4.4 Mapping undermining around the entire wound perim- eter. (Courtesy of Evonne Fowler, MN, RN, CETN.)
the total wound area when undermining is calculated, com- pared with measurement of the SA alone. Figures 4.6 and 4.7 demonstrate the extent of the tunneling process in a trochan- teric pressure ulcer.
In a principal component analysis of the Pressure Ulcer Scale for Healing (PUSH) (see Chapter 5), the addition of a tunneling measurement was not found to improve the valid- ity and reliability of that tool; therefore, the measurement is not part of the tool components.12 Facilities and health- care organizations need to determine if the measurement of undermining and tunneling should be part of wound docu- mentation and thus included in the wound care policies and procedures.
Choose a Consistent Method
Three methods for measuring undermining and tunneling are described below. Choose one and use it consistently (see Figs. 4.8 and 4.9).
Method 1
1. Map undermining around the entire wound perimeter by inserting a moist, cotton-tipped applicator into the length of the undermined/tunneled space and continuing around the perimeter. Dip the cotton tip into normal saline before insertion, so it slides in easier and is less likely to cause tissue trauma (Fig. 4.4).
2. At the end point, do not force further entry, but gently push upward until there is a bulge in the skin. Mark the points on the skin with a pen and connect them. Measure the length Some wound experts claim that the true extent of a wound is not
known unless undermining/tunneling is measured.12 Figure 4.4 shows the larger perimeter of a wound when undermining is mapped, and Figure 4.5 compares measurements over time of
FIGURE 4.5 Wound healing trajectory: recovery of a pressure wound.
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FIGURE 4.7 Same wound as in Figure 4.6 with surgical dissection demonstrating the extent of the tunneling process, forming a sinus tract. (Copyright © J. Wethe.)
2. Wet the cotton-tipped applicator with normal saline and insert gently into tunnel. Mark the place on the skin where the cotton tip causes a bulge, and withdraw the cotton-tipped applicator.
3. Grip the cotton-tipped applicator at the point at which the skin and wound edge meet, and withdraw it. This is the length of the tunnel.
and width, and multiply these measurements to calculate the overall undermined estimate (explained below).
Method 2
1. The Sussman method for wound measurement applies the four cardinal points of the clock method to measurement of undermining and tunneling.9 The 12:00 position is toward the head unless otherwise noted.
FIGURE 4.6 Unobservable tunneling. (Copyright © J. Wethe.)
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3 1 2
FIGURE 4.8 Wound with tunneling before insertion of a cotton-tipped applicator. Note: (1) Ulcer reoccurrence at site of old scar tissue; (2) Skin bridge between two open ulcers; (3) Surrounding skin has unblanchable erythema; wound edges rolled under demonstrate chronic infl ammatory phase. (Copyright © B.M. Bates-Jensen.)
1
FIGURE 4.9 Same wound as in Figure 4.8. The wound’s overall size is much larger than the surface open area. Tunneling is present. Note the bulge from the end of the cotton-tipped applicator. (Copyright © B.M.
Bates-Jensen.)
RESEARCH WISDOM
Accuracy and Reliability of Wound Undermining Measurements
Taylor11 studied the variability of measurements of wound undermining among physical therapists trained in the Sussman wound undermining measurement method. Her fi ndings show that the most signifi cant variation occurred when the 12:00 position coincided with the greatest length of the wound’s open SA, which infl ated the area measurements.
The results of studying measurements by 39 physical therapists over a 4-week period demonstrated several inter- esting fi ndings. Three common errors occurred: misread- ing the measuring device, transferring the numbers, and calculating. As would be expected, there were more errors in measurement when the wounds were smaller. Overall, the variation was 10.5% or less. Validation of the measur- ing technique was proven highly reliable, suggesting that this measurement can be used to document progress in the heal- ing of undermined wounds.11
4. Place the length of the cotton-tipped applicator up to the withdrawal point against a centimeter ruler or measure from wound edge to mark on skin as in method 1. Record the length measurement.
Method 3
1. Test the perimeter for undermining with a cotton-tipped applicator, and then select the longest tunnel to measure.
2. Use the clock method to identify the location(s) on the wound perimeter where tunneling is present, and then track the tunnel over time.
Calculating the Overall Undermined Estimated Size
To derive an estimate of the overall undermined estimated size of the wound area, add the measurements of undermining/
tunneling to the SA length and width to derive the overall length and overall width. Next, multiply the overall length by the overall width.9 For example, using the clock method:
12:00–6:00 length + 12:00 undermining + 6:00 undermining
= overall length
3:00–9:00 width + 3:00 undermining + 9:00 undermining = overall width
Overall length × overall width = overall estimated area
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80 70 60 50 40 30
healed
Weeks in Study at 2 Week Intervals
% wounds Healed
Trajectory of Healing for Healing and Non-Healing Diabetic Ulcers
not healed
20 10 0 FIGURE 4.10 Trajectory of healing for heal-
ing and nonhealing diabetic ulcers. (Source:
Robson MC, Hill D, Woodske M, et al.
Wound healing trajectories as predictors of effectiveness of therapeutic agents. Arch Surg. 2000;135(7):773–777.)
The product is a single number that can be monitored and graphed to show the trajectory of healing over time, as indi- cated by the dashed line in the graph in Figure 4.5. This fi gure also shows how the overall undermined estimated size com- pares with the SA estimate.9 If only the open SA is monitored for change in size, the wound appears signifi cantly smaller than it actually is, and information about incremental changes in size is lost.
Graphing the Trajectory and Percentage of Healing
Wound SA and undermining measurements can be plotted on a graph to show a trajectory of healing that identifi es those patients whose wounds are on track to heal and those whose wounds are not healing. The points on the trajectory can be used as end points to compare results, rather than complete healing.13 Graphs showing the wound healing trajectory, such as the one shown in Figure 4.10, are a very useful visual method for monitoring healing over time. Graphing is recommended for tracking the scores obtained using the Pressure Ulcer Scale for Healing (PUSH) tool (see Chapter 5). Recently, the wound healing trajectory has been suggested as a method for tracking signifi cant points along the continuum of healing, rather than a single end point, when determining the effi cacy of treatment interventions.13
Controlled clinical trials of many types of wound healing products use reduction in ulcer SA as the dependent variable, and results are reported as a percentage of reduction in unit area per unit time (cm2/mm2 or %/day/week).14 Percentage of heal- ing per unit of time (PHT) refers to the decrease in wound area from the baseline to the day of measurement for each reevalu- ation period (e.g., per week) as a percentage of the wound size.
PHT rates have been used to calculate the linear daily or weekly healing rates analyzed for different wound etiologies (pressure ulcers, venous ulcers, and diabetic ulcers). (Refer to Part II for information about different wound etiologies.) These rates are now becoming the standard predictor of whether the wound will heal, and are also useful for comparing the results and costs of different interventions.2–4,15–17
Steps for Graphing the Trajectory and Percentage of Healing
Creating a trajectory of healing involves the following basic steps. Note that the graph can be generated as part of a database program or manually drawn on graph paper:
1. Perform the size measurements following a defi ned protocol.
2. Calculate the total wound area (cm2) or the percentage change in size. Methods of calculating the PHT vary. See Exhibit 4.4 for an example. Plot the wound healing curve on a graph. This requires two axes: horizontal and vertical. The horizontal axis represents time, and the vertical axis rep- resents size in square centimeters or percentage of change.
Time should be graphed at consistent intervals (e.g., weekly, with the baseline week 0). See Figure 4.10 for example.
Using the Trajectory Graph to Determine Phase of Healing A great deal of information can be gleaned from trajectory graphs. For instance, consider again the simple trajectory graph in Figure 4.5. Note the signifi cant variations in the extent of the wound between May and July. However, notice the linear reduction in wound extent from September to December. As the wound healed, undermined/tunneled spaces closed, tissue integrity was restored, and the overall size was reduced.
Graphing can also show how changes in the undermined esti- mate parallel the changes in wound phase. For example, notice the abrupt jump in wound overall undermined estimate from 42.25 cm to 122.43 cm; this frequently coincides with the early prolifera- tive phase. The expansion of the wound extent refl ects the effects of wound debridement on loss of subcutaneous tissue integrity (the separation of fascial planes), producing tunneling. Loss of subcutaneous tissue integrity produces increased risk of infection, but subcutaneous tissue integrity is restored as the wound pro- gresses through the proliferative phase to the remodeling phase.
Using the PHT to Predict Healing and Nonhealing
As you can see, percentage reduction in wound size—rather than the actual size measurements—is a valid and useful method for predicting wound healing rates and tracking the healing of pressure ulcers, venous ulcers, and diabetic ulcers.16,18,19
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Comparing Healing Rates
Venous ulcers that healed in 4 weeks or more had an initial heal- ing rate of 0.049–0.065 cm per week, and diabetic ulcers had a rate of 0.063 cm per week, suggesting that there may be a fairly uniform rate of healing for chronic ulcers, regardless of etiol- ogy.23 Because repairing wounds appear to heal at the same rate, there should be no correlation between initial ulcer size and the rate of healing. By using the 0.062 cm per week rate of healing for full-thickness chronic ulcers, a 4-week period could be suf- fi cient to establish a healing trend.23 Before this recommenda- tion can be used as a standard for all chronic wounds, consider the fi ndings that the trajectory for healing differs for partial- thickness and full-thickness ulcers. Linear advancement of the wound margin was 0.056 mm per day (0.0392 cm per week) for partial-thickness ulcers and 0.021 mm per day (0.0147 cm per week) for full-thickness ulcers. Median time is the time by which at least one-half of the patients have healed. Median time to healing for the partial-thickness ulcers was 28 days, and it was 56 days for full-thickness ulcers. These fi ndings suggest that norms for duration and rate of healing are specifi c to the level of tissue injury (Exhibit 4.6). Polansky and vanRijswijk suggest using the median time of healing for study groups, rather than The conclusion supported by a number of studies is that
pressure ulcers and leg ulcers (venous and diabetic) that do not reduce in size between 30% and 50% in a 2- to 4-week period are not on a healing trend and are less likely to heal than ulcers that do reduce by these amounts.5,15,16,19–21
Healing trajectories are signifi cantly different for healers and nonhealers (see Fig. 4.10)13. By plotting the percentage of change on a graph, you will create a trajectory that you can then use to compare against these numbers. This will indicate whether the wound is following a course for healing or for nonhealing.
In addition, review of the PHT at clinical decision points can be extremely valuable in helping you identify early on the patients who require more aggressive and possibly more expen- sive interventions.
It can also help you identify those who are likely to heal with standard care. Shifting of the wound healing trajectory from an impaired course to a more ideal course can also be one way to evaluate the effi cacy of the treatment plan.
It is clear that the precision of wound measurement and the method of calculating the rate of change can and should infl u- ence clinical decision making. Clinicians today are responsible for setting the goals of treatment and differentiating wounds that will go on to heal with standard care from those that should be triaged to adjunctive therapy.
Limitations of PHT Calculations
The calculation method presented in Exhibit 4.4 is commonly used to measure healing. However, this method can exagger- ate the progress made by larger wounds relative to smaller ones, and the percentage of reduction in area can minimize the actual progress made by large wounds relative to the progress made in small wounds.19 Wounds of different sizes and shapes present special problems. To compensate for these problems, Gilman22 proposed a formula for measuring the wound perim- eter change over time (Exhibit 4.5). Tallman et al.3 found that using initial wound size as the baseline for percentage of change in size calculation to determine the weekly healing rate gave healing rate instability from week to week, which decreased the ability to predict complete healing. They created another method to compare healing rates, which takes the mean of all previous healing rates between each visit (which becomes the mean adjusted healing rate) and uses that rate as the base- line size to calculate the percentage of change. This method improved healing rate stability from week to week and allowed prediction of complete healing as early as 3 weeks from start of therapy (p <0.001).3
CLINICAL WISDOM
Healing Rates
Healing rates should not be used to predict a specifi c antici- pated healing date because factors that affect healing can- not be controlled. The rates should be used to help clinical decision making and identify effective and ineffective treat- ments. Accurate measurement of wound size is the basis for reliable predicting.
EXHIBIT 4.5
Gilman Method of Measuring Wound Healing Using the Wound Perimeter
d = DAp
d = units of distance; d represents the average distance of advance of the wound margin over the study time T, in a direction toward the wound center DA = the difference in area of the wound before and after
the study time T
p = the average perimeter before and the wound perimeter after time T
Reprinted with permission from T.H. Gilman, Parameter for Measurement of Wound Closure, Wounds: A Compendium of Research and Practice, 1990;2(3):95–101. Health Management Publications.
EXHIBIT 4.6
Factors that Signifi cantly Affect Healing Outcomes
● Initial SA size: Larger ulcers take longer to heal.4,16
● Duration: Ulcers of short duration are most likely to heal.4
● Healing rate: A 30% to 50% reduction in area size in the fi rst 2 to 4 weeks predicts healing.4,15,16,19
● Circulation: Moderate arterial insuffi ciency (ankle-bra- chial index (0.5–0.8) increases risk of delayed healing.2
● Nutrition: Full-thickness pressure ulcers heal faster with proper nutrition.16
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