ASSESSMENT OF THE DYNAMIC EFFICIENCY OF COMPRESSION STOCKINGS WITH QUANTITATIVE DIGITAL PHOTOPLETHYSMOGRAPHY

Background: The resting pressure exerted on the leg by a compression s tocking can be measured exactly. It would be more useful, however, to determine the dynamic efficiency of the stocking during exercise, whic h has not been possible in the past because of the lack of a suitable measuring technique. The technique of digital photophlethysmography (D -PPG) seems to be particularly suitable for this purpose since it is a calibrated device with a flat optical measuring head. Objective: To s tudy the correlation between the dynamic efficiency of compression sto ckings and the clinical stages of chronic venous insufficiency (CVI) a nd the functional degree of calf pump insufficiency by means of quanti tative photoplethysmography. Design: Prospective controlled study of p atients with chronic venous insufficiency of different degrees using c alf length stockings of two pressure classes (20-30 mmHg and 30-40 mmH g, Jobst Co., Germany) and the quantitative photoplethysmography D-PPG (Elcat Co., Germany). Setting: Department of Dermatology, Medical Cen tre of Berlin-Buch, Berlin (Germany). Patients and Method: The study, which is not yet completed, comprises the following clinical and PPG g roups (Table 1, overlapping classification). In most of the PPG groups two subgroups were made according to the improvement in venous functi on found in the tourniquet test. This fine classification possibly cou ld be an advantage over the more rigid clinical classification accordi ng to Widmer. The D-PPG sensor was inserted under the stocking at the standard location above the inner ankle. The increase in pressure caus ed by the measuring head had been calculated on the basis of a pressur e-stretching diagram (around 0.4 kPa, i.e. 3 mmHg only). Thus it was n ot necessary to cut a window in the stocking as has been recommended i n the past. For the dynamic measurements the usual software program of the device and the standard exercise test were used (eight dorsal ext ensions in the sitting position). Repeated measurements were performed without the stocking and with a stocking of each of the two pressure classes following a strict protocol. Results: In healthy legs the comp ression stockings did not show any dynamic efficiency. The mean T-o va lues remained almost unchanged, namely 40 s without a stocking, 39 s w ith the 20-30 mmHg stocking and 37 s with the 30-40 mmHg stocking. In the CVI stage I group the 20-30 mmHg stocking effected an improvement in all the cases whereas the 30-40 mmHg stocking showed an improvement in only some of the cases. In the CVI stage II group the 20-30 mmHg s tocking produced a slight prolongation of T-o in all the cases. The 30 -40 mmHg stocking failed to produce an improvement in two cases and in some of the legs T,decreased; others improved more than with the lowe r class stocking. In the CVI stage III group T-o improved in more than 90% of the legs with the 30-40 mmHg stocking but in only 75% with the 20-30 mmHg stocking. In the D-PPG stage I group the 20-30 mmHg stocki ng produced an improvement in all the legs whereas the 30-40 mmHg stoc king brought about an improvement in only one case. In the D-PPG stage IIa group all legs but one showed the highest dynamic efficiency with the 20-30 mmHg stocking. The D-PPG stage IIb group was especially inh omogeneous. Compared with the findings without a stocking, the 20-30 m mHg stocking caused an increase of T-o in all the cases, at least of s light degree. The 30-40 mmHg stocking did not result in any improvemen t in two cases. In some cases it triggered an increase of T-o which wa s lower, and in others higher, than with the 20-30 mmHg stockings. Thu s it is not possible to give a general recommendation for the optimal compression stocking, especially in this subgroup. In the D-PPG stage III group the 30-40 mmHg stocking improved the initial findings in all the cases, which was true for the 20-30 mmHg stocking in only five ca ses. Only in two cases was T-o improved more with the stocking of the lower pressure class. Conclusions: All results are somewhat preliminar y since the planned number of cases has not been reached in the D-PPG stage I and III groups. For this reason we did not undertake statistic al analysis. Nevertheless, the results demonstrate interesting trends which are in good congruence with each other (cf. Table 2). With healt hy legs there was no dynamic efficiency of either of the two stocking classes. The 20-30 mmHg pressure class was superior in the D-PPG stage T and IIa groups. The 30-40 mmHg stockings are indicated in the D-PPG stage IIb and III groups but individual dynamic measurements with bot h pressure classes may be necessary. There is still another point of a ssessment. The maximum increase of T-o caused by the respective stocki ng with the best efficiency was around 50% in the D-PPG stage I group, 60% in the D-PPG stage IIa group, 80% in the D-PPG stage IIb group an d 100% in the D-PPG stage III group. Thus it can be concluded that the dynamic efficiency of appropriate compression stockings is very high and even increases with the severity of insufficiency. In absolute ter ms, the mean T,values of the D-PPG stage IIb and III groups did not re ach the normal range, but in the stage I and IIa groups it even return ed to normal.