title: An evaluation of the standard bubble time technique for the measurement of extracorporeal blood flow.
abstract: Manual BT is the standard technique to use when measuring Qb for dialysis. An electro-optical system (QB-1) was devised for the measurement of BT and its relationship to real Qb. We investigated the accuracy of standard manual timing methods, the roller pump induced effects of high amplitude low frequency pulses (HALFP), the fundamental pulse of flow (Lp), and the effect of hematocrit (HCT) on BT. Blood with 15, 24, and 38 HCT was used. During dialysis, BT's were measured manually and by QB-1. With Qb greater than 200 ml/min, variations in length became insignificant. HCT did not influence BT at the values studied. In conclusion, 1) QB-1 is more accurate than manual measurements of BT, especially at higher Qb. 2) Qb greater than 200 ml/min dampens the effects of HALFP at any length of tubing. 3) HCT has no effect on BT.
mesh_terms: D000704:Analysis of Variance; D001783:Blood Flow Velocity; D005112:Extracorporeal Circulation; D006801:Humans