Original Article

Some Considerations Regarding the Use of the Delta Lev-L-Sentry Low Level Alarm System

Providence Medical Center, Portland, OR

^* Direct communications to: Howard G. Walton, Providence Medical Center, 4805 NE Glisan, Portland, OR 97213

Abstract

The possibility of infusing an air embolus during extracorporeal circulation is of concern to every perfusionist. The perfusionist uses a variety of devices to prevent such an accident. The Delta Lev-L-Sentry alarm system is one such device. It consists of a disposable sensor tape, an electronic sensor head, and a power/control box. The sensor head and tape are attached to the oxygenator. The unit will warn of a low level situation in the oxygenator when the fluid falls below the preset sensor tape position. This paper describes two possible situations where the Delta-L-Sentry alarm system may not activate properly, and one situation in which it will activate improperly.

A protein coating from the blood can result in a low sensitivity of the sensor tape. This, combined with a rapid draining of the oxygenator, can produce a false negative alarm. To avoid this false negative alarm mode it is recommended that the sensor tapes be cut and attached at the prescribed 50 degree angle (from the horizontal) regardless of the angle supplied by the manufacture. Another situation which can cause a false negative alarm mode is spilling electrolyte solution on the sensor tape. This can be avoided by protecting the sensor head. The one instance of a false positive alarm mode was caused by electrocautery interference during surgery. The use of a grounding cable will reduce the interference thus avoiding the false positive alarm signals.