Effects of compression bandages and a protection boot on sub-bandage pressure and lymph flow on the distal equine limb

摘要

Horses on box rest or with reduced mobility after injuries often suffer from distal limb oedema. It also occurs in aged horses with chronic limb diseases. Polo wraps are commonly used to avoid oedema, however a disruption of lymph flow by tightly applied bandages might occur. In this prospective, randomised, experimental study the effect of two elastic compression bandages made of knitted fabric (EquiCrown (R) active ("active") and EquiCrown (R) fit ("fit")) on lymph flow and sub-bandage pressure was investigated. In comparison, a standard protection boot made of a hard shell and neoprene lining, commonly used during workout, was also included. In five warmblood research horses without forelimb disease, all three bandage types were randomly applied. Compression bandage application was always done by the same person. A period of 5 minutes for acclimatisation was maintained between bandage changes. For each bandage type lymph flow and sub-bandage pressure was assessed. To visualize lymph flow, indirect lymphangiography was performed under sedation. Briefly, after intracutaneous bolus injection of iodinated contrast agent at the coronary band, lateromedial radiographs of the respective distal forelimb were taken before and 10 minutes after bandage application. Radiographs were assessed for consistent visible lymphatic vessels (yes/no). On the contralateral limb, 16 pressure sensors were placed underneath the bandage on predetermined localisations (four rows with one sensor at the dorsal, lateral, palmar and medial aspect, respectively) to measure sub-bandage pressure. Data was collected over a minimum of 60 seconds with a frequency of 1 Hz. Parameters were post-hoc analysed for mean pressures, peak pressures and distribution of pressure over the distal limb by descriptive statistics and non-parametric tests (Wilcoxon signed-rank test) for comparison within each individual (significance was set at p < 0.05). Continuous distal limb lymph flow was visible on the distal limb in all three bandage types (compression bandages "active" and "fit", standard protection boot). Meander-shaped lymph vessel course were found in four out of five horses. Total pressure on the distal limb (accumulated pressures of all 16 sensors) did not differ between both compression bandages. Compared with the protection boot, pressure was significantly higher beneath the compression bandages (p < 0,001) with a more homogeneous distribution of the pressure. In 91.3 % (compression bandage "fit") and 88.8 % (compression bandage "active") sub-bandage pressure was higher than 30 mmHg, and in 66.3 % ("fit") und 60.0 % ("active") lower than 70 mmHg. This range (30-70 mmHg) is considered to be effective in humans to reduce limb oedema. The median pressure was 50.6 mmHg (interquartile range 23.4 mmHg "fit")/55.3 mmHg (IQR 32.8 mmHg "active") on the dorsal, 48.3 mmHg (IQR 19.0 mmHg "fit")/39.9 mmHg (IQR 29.8 mmHg "active") on the lateral, 49.7 mmHg (IQR 93.3 mmHg "fit")/51.6 mmHg (IQR 57.9 mmHg " active") on the medial, and 130.7 mmHg (IQR 117.5 mmHg "fit")/133.1 mmHg (IQR 147.0 mmHg "active") on the palmar aspect of the limb. The anatomical position of the flexor tendons on the palmar aspect might contribute to the higher pressures obtained in this area due to smaller contact zone with the bandages. In conclusion, compression bandages maintained a continuous lymph flow on the distal limb and did not disrupt circulation of applied contrast media.