Do antisiphon valves reduce flow irregularities during vertical displacement of infusion pump systems?

Vertical displacement of syringe pumps may cause irregular drug delivery du e to hydrostatic pressure changes in the infusion line. The extent of flow fluctuations depends on the internal compliance of infusion lines, syringes and syringe pumps. We evaluated whether pressure regulation by antisiphon valves (ASV) reduces the flow variation during vertical displacement of 50 mi standard syringes and infusion pumps. An infusion assembly comprising a standard 50 mi ED Plastipak(R) or a 50 mi Fresenius syringe, with syringe pump and 2m low compliance infusion line w as used for in vitro measurement of fluid delivery. The assembly was tested without ASV and with two ASVs of differing operating pressure (AST:75: val ve opening pressure=75 mmHg; ASC:155, 155 mmHg). Retrograde aspiration volu me, zero-drug delivery time and valve opening bolus were determined after l owering the syringe pump by 50 cm. After elevating the syringe pump to its initial position the ensuing infusion bolus was recorded. Without an antisiphon valve the observed zero-drug delivery times after low ering the syringe pump were (mean+/-SD) 2.4+/-0.2 min using the ED Plastipa k(R) syringe and 4.09+/-0.55 min using the Fresenius(R) syringe. Introducti on of the antisiphon valve prolonged the zero drug delivery time 58% (ASV:7 5) and 88% (ASV:155) in the ED Plastipak(R) syringe assembly and 43% (ASV:7 5) and 81% (ASV:155) in the Fresenius(R) syringe assembly (P<0.001). Antisiphon valves worsen flow irregularities caused by vertical displacemen t of syringe pumps and when used with delivery of concentrated inotropic dr ugs at low infusion rates, they may aggravate haemodynamic consequences of inconstant drug delivery.