Monday, September 12, 2011

How "Air in-line' alarm work

Ultrasonic sensors provide key safety feature for infusion pumps

Infusion pump is that accurately dispenses medication and fluids, such as morphine and nutrition, into a patient’s circulatory system. A key safety feature of the pump is an ‘air-in-line’ detection system, which monitors for the presence of air bubbles in the fluid.
“Accurate detection of air bubbles is vital in maintaining the health and recovery of patients, Air embolisms can lead to serious complications in blood flow and the heart’s operation.”

There are other technologies that are used to detect air bubbles such as infrared. However, ultrasonic technology provides the most accurate and reliable detection. .



How Ultrasonic Sensors Work

Ultrasonic sensors depend on two separate devices: an ultrasonic transducer and a detector. An ultrasonic transducer is any device that converts energy into an ultrasonic frequency. Though dog whistles and several other devices can convert mechanical energy into an ultrasonic frequency, ultrasonic transducers are usually made from piezoelectric crystals that can change size when a voltage is applied to them. When an alternating current is applied to a piezoelectric crystal, it vibrates extremely fast and produces an ultrasonic sound wave. The detector is also made of a piezoelectric crystal, but produces a voltage when an ultrasonic frequency comes in contact with it, effectively producing the opposite results. A sensor calculates the time that it takes in between broadcasting the ultrasonic frequency and receiving the incoming waves.

How to detect air in line 

 If there is fluid in the infusion line between the sensors then a signal is received, but when air passes through a reduced signal is received. This change in signal generates an alarm, alerting the user that an air gap is present, and the pump automatically stops infusion.



 

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