Tapping enhances vasodilation for venipuncture even in individuals with veins that are relatively difficult to...

This study evaluated whether tapping enhances vasodilation in individuals with veins that are relatively difficult to palpate.

Twenty participants (4 men and 16 women, aged 19-22 years) with cutaneous veins that were relatively difficult to palpate even after tourniquet application were recruited. A crossover trial with/without tapping (10 times in 5 s) was performed under tourniquet inflation on the upper arm. Vasodilation was evaluated by venous cross-sectional area, depth of the vein, and elevation of the overlying skin by ultrasonography. Venous palpation scores were also measured. The degree of improvement was estimated by simulation.

In total, 60% of participants "sometimes" or "often" experienced unsuccessful venipuncture. After the tapping procedure, the venous cross-sectional area significantly increased (14.6 ± 9.12 mm² for control and 15.2 ± 9.79 mm² for tapping) and venous depth significantly decreased (4.57 ± 2.31 mm for control and 4.23 ± 2.41 mm for tapping). A simulation study using these values suggested that tapping increased the longitudinal and crosswise successful ranges of venipuncture by 5-6%.

Tapping in this study enhanced the vasodilation of cutaneous veins that are relatively difficult to palpate. The effectiveness of various vasodilation methods may be compared through the estimation of improvement.