A medication infusion system which includes an infusion line for introducing medication to a peripheral vein of a patient. The infusion system includes a pump for delivering the medication and a pressure transducer within the infusion line for converting sensed fluid pressure waves to electrical signals. An amplifier is provided within the system for increasing the strength of the electrical signal. A gain control amplifier is electrically connected within the system for maintaining the electrical signal at a predetermined amplitude regardless of input variations. A tracking filter is provided within the system to provide an electrical signal representative of the patient's respiration rate over a preselected full clinical respiration rate range. A microprocessor is provided within the system for deriving from the electrical signal a control signal for controlling the operation of the pump. The microprocessor includes the ability to determine the presence or absence of the electrical signal representative of the patient's respiration rate, a comparator for comparing the rate signal with a preselected respiration rate and a storage capability for storing the rates and preselected rate values. The system further includes a motor control for providing a signal to the pump for actuating the pump in preselected increments when directed by the microprocessor.