An Infusion Pump for Arterial Pressure Recording

Abstract

The purpose of this communication is to describe an infusion pump which will make possible the continuous recording of blood pressure over long periods without an anticoagulant using high frequency recorders of the Hamilton, Sanborn, or Statham type. The principal requirements for such a pump are as follows: 1) it must deliver saline smoothly at a very slow constant rate into the artery from which the pressure recording is being taken; 2) it must not alter the magnitude of the pressure recorded but it must build up and sustain a pressure exceeding arterial by a small increment; 3) it must be provided with a device which will protect the artery and the pump in case of obstruction of the outlet because of a blood clot or for any other reason; 4) it must not introduce mechanical damping which would impair the frequency response of the manometer. The pump described below appears to meet these specifications.

In Fig. 1 is shown a schematic plan of the pump. The syringe holder and plunger drive assembly, which may be obtained commercially,∗ is mounted on any convenient base. It consists in a spur gear (not visible) which runs inside block A and drives rack B; this, in turn, drives a 50 cc standard syringe which is held in clamp C. It is necessary to ream the threaded hole in block A at the arrow to fit a piece of 1/4′′ drill rod D. This rod passes through the spur gear to which it is attached by a pin and terminates in a radio dial knob at E. The other end of the drill rod goes through a standard 1/4′′ radio panel bearing assembly in a vertical partition of masonite F, and terminates in spur gear G which meshes with spur gear H on the reduction box.