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2. Circumferential Methods (C) (1,6,8-11,15-19,23,26-28,30,31,33,34,36,40,41,43,46)
A total of 16 papers on circumferential measuring method have been reviewed; among them, only 4 were specifically focused on the validation of this technique (9,26,27,31). Limb volume can indirectly calculated from circumferential measurements made using a flexible tape. This technique is very popular in the clinic setting. The arm swelling is evaluated by different methods: in the first method, circumferential measures are taken at given points along the limb, and the points are measured at each reassessment (9); in the second method the calculation of the volume is done using a geometrical approximation formulas. In this last method, the volume of each arm is calculated using two basic formulas, which are cylinder and truncated cone [frustum] formula. The limb is divided into sections, with each section representing a cylinder or cone. The final volume is determined by adding
the volumes of the sections together. Several authors reported
the formulas normally used to calculate the volume of whole
arm (4,5,9,19,26,27,31,40,41). Other works focused the attention on the
hand volume evaluation (26,27,40). They tackle an issue of how
simplify a so complicated limb segment. They suggest
different geometrical solutions and explain measure procedures.
Papers on the comparison between water volumetric method
and circumferential methods represent the highest percentage of the reviewed articles (60%) (6,8,16,19,23,24,26-28,30,31,33,34,40,46). It can be
explained easily if consider that the first technique is the gold standard and the second one is the most widely used method.
In particular, two works focused the attention on accuracy problem in volume detection (1,29). Accuracy depends on various factors, but the most important are the choice of the geometric formula and the spacing of the measurement. Sitzi (41) compared the cylinder and frustum formulas and stated that the frustum formula is intrinsically the most accurate. Literature about accuracy of circumferential method is here reported (1,9,15,23, 26,40,46). Accuracy clearly depends on the spacing between and the number of measurements. In general measurement are made every 4-8 cm along the axis of the limb (4,5,23,31,40,43).
The estimation of arm volume using circumferential arm measurement is subject to several potential errors. One is related to the interobserver variation. Different degree of tensions applied to measuring tape of the limb leads to different volume estimations (46). Reliabilities have been studied at different measure intervals and compared using different formulas. In a Sander’ s article (40) the Inter Class Correlation index (ICC) has been calculated using cylinder and frustum formulas in three different measure intervals – 3,6 and 9 cm. The results have shown different values of ICC to depending on anatomical segments; ICC (2,1) is equal to 0.99 for arms, while ICC (2,1) for hands is between 0.91 and 0.98. Reliability aspects are studied by several authors (1,9,11,15,18,19,23,26,40, 46).
3. BioimpedanceMethod(BI)(1,10,11,13,18,20,22,32,37,38,43,48)
4. A total of 12 papers on Biompedance measuring method have been reviewed and among them, 3 papers describe in details this technique (22,37,48). Bioimpedance measures tissue resistance to an electrical current to determine extracellular fluid volume. When a current, conventionally of 200–800 mA, is applied to
THE EUROPEAN JOURNAL OF LYMPHOLOGY - Vol. XXIX - Nr. 75 - 2017
the body surface through a set of cutaneous electrodes, it is transmitted through water-containing component within the tissues. The current flow through biological tissue is frequency-dependent. At low frequency, current passes through the extracellular fluid (ECF) space and does not penetrate the cell membrane. At high frequencies, however, the current passes through both the extracellular and intracellular fluid. Based on these concepts, a value for impedance can be calculated. When bioimpedance is applied to the quantitative analysis of lymphedema, the pathological accumulation of extracellular fluid is mirrored by a decrease in the measured impedance, in proportion to the degree of extracellular fluid accumulation. Thus, the impedance value can be converted into an index score, which reflects volume measurement.
Since, impedance decreases while extracellular fluid volume increases. One significant advantage in bioimpedance is the ability to measure bilateral limb lymphedema (1). The measured values of bioimpedance are conventionally expressed as the ratio of the normal limb/abnormal limb. In the absence of segmental excess fluid volume accumulation, this ratio should approximate one; as lymphedema severity increases, the measured ratio rises proportionately. Regarding to the reliability of method, the literature is in contrast: some authors affirmed bioimpedance cannot differentiate between the different types of extracellular fluid, and thus the positive results from bioimpedance resting in the first few months after the breast cancer treatment should be treated with caution (1); on the other side some authors state that bioimpedance spectroscopy should have specific sensitivity to detect latent lymphedema, since it measures only the accumulation of extracellular fluid (ECF), of which lymph is a main component, rather that overall volume (1,11,13,18,48). There is a lack of works on the comparison between bioimpedance and water volumetry methods in terms of errors and reliability. According to Ridner et al (37), in bioimpedance, the use of adhesive electrodes placed on fixed anatomical landmarks reduces the risk of user errors.
5. PerometryMethod(P)(1,10,11,15,18,20,38,43,45)
A total of 9 papers on perometric measuring method have been reviewed. Perometry measures arm volume using infrared light. The machine has a square-shaped sliding frame, which surrounds the perimeter of the limb. This frame contains rows of infrared light emitters and sensors on opposite sides. When the arm is place inside the frame, it interrupts the emitted infrared beam on two planes. This provides two perpendicular diameter measurements of the arm segment. Thus, it is possible to estimate for each measuring point (in general with an intervals of 4.7 mm) the correspondent diameter and then to calculate the volume of the limb. This technique is considered by several authors has excellent intra and inter-observed reliability(1). Theintraraterandinterratercorrelation coefficient between these techniques had satisfactory value racing from 0.937 and 0.997. The infrared optoelectronic volumetry has the best reliability and is the only method that provides no difference between intrarater and interrater reliability. It means that different therapists can use it on the same patient. According to Piller (35), the accuracy of perometry can be compared to the accuracy of the water displacement
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