Role of the Elasticity of Rubber in the Controlled Administration of Drugs

Abstract

The energy stored in an extended elastomeric reservoir can be usefully employed in the controlled delivery of drug solutions at constant rates of flow through a fixed resistance. The absolute level and constancy of pressure presented to the upstream end of the flow restrictor can be related, respectively, to the geometry and composition of the elastomeric reservoir. (The reservoir is to contain, in its distended form, the volume of drug to be delivered to the human venous system.) It has been established that the defining criteria for minimizing static pressure loss in the reservoir and for maintaining constancy of pressure through most of the delivery interval are stress decay and hysteresis, as measured in uniaxial stress-strain testing. The elastomeric composition most successfully meeting these requirements has been found to be non-reinforced isoprene rubber, crosslinked with a peroxide.

The flow Rate Accuracy of Elastomeric Infusion Pumps After Repeated Filling

“…This flow pattern is common to all elastomeric pumps (18-20) and is due to variations in pressure within a stretched elastomeric reservoir (21). This variation in infusion rate is considered clinically acceptable with no hazard to patients (22, 23).…”

“…The examined elastomeric pumps initially infused at a rate faster than their nominal flow, and then returned closer to their set rates up to the complete deflation. This flow pattern is common to all elastomeric pumps ( 18 - 20 ) and is due to variations in pressure within a stretched elastomeric reservoir ( 21 ). This variation in infusion rate is considered clinically acceptable with no hazard to patients ( 22 , 23 ).…”

A novel device for patient‐controlled sedation: laboratory and clinical evaluation of the Baxter Intermate LV250 infusor and patient‐control module

“…The pressure-volume relationship within the bladder is a function of the physical characteristics of the elastomer and the elastic recoil that is generated by the tension of the distended bladder [5]. The pressure within the bladder is described by LaPlace's Law which states that the pressure generated is inversely proportional to the radius of the sphere and proportional to the surface tension of the bladder skin, or:…”

Laboratory assessment of the Baxter disposable patient‐controlled analgesia system

“…The pressure-volume relationship is determined by the geometry of the balloon, and is related to the composition of the elastomer and biaxial stress generated within the distended elastomeric reservoir [8]. During fluid release, the elastomeric balloon deflates primarily in the axial direction, while the distended radial diameter (hoop stress) is maintained.…”