Device-level diagnostics

In addition to device-level diagnostics, networked final control elements, process controllers, and transmitters can provide loop level diagnostics that can detect loops that are operating below expectations. Process variability, time in a limit (saturated) condition, and time in the wrong control mode are metrics used to detect problems in process loop operation. 

Some of the first applications of SBC in medical applications were for drainage units. The units are clear to allow ease of reading fluid levels, and breakage resistant to contain fluids if the parts are dropped or impacted. Applications have expanded in other medical devices and diagnostic equipment, including yankaeurs, centrifuge tubes and medical films. Other application areas include safety needles and various respiratory care devices. 

Use of self-diagnostics at systems and device level to reduce mean time to repair and overall SIF PFD. Use of deenergize to trip logic. 

Four major areas of electrochemistry related to medical diagnostics have been reviewed. Blood pH and gas measurements as well as ISE s represent relatively mature areas which enjoy widespread commercialization. New approaches should yield devices which have superior performance and which are less expensive to produce. Enzyme electrodes and electrochemical immunoassay arc still largely experimental, but the intense level of current research effort coupled with some interesting recent developments should lead to commercial success over the next decade. 

Hospital and commercial diagnostic testing laboratories rely on monoclonal antibody tests to measure the amounts of specific proteins, hormones, or drugs in blood. Monoclonal antibodies tagged to fluorescent dyes are also used with lasers to determine the kind of tumor a patient has, to track the number of tumor cells, and to monitor the level of immune system cells. The CD4 count test, important to patients with HIV infection, uses monoclonal antibodies and a laser-driven device that checks cell by cell for the CD4 protein, the marker for the critical immune system cell. The same technology and a set of antibodies to immune system cell proteins are used to diagnose children suspected of having inherited an immune system deficiency. 

Precision is normally one of the easiest performance parameters to measure for an in vitro medical diagnostic test. Multiple tests are run using the same sample and the standard deviation is calculated. Precision is not so easily tested for in vivo medical diagnostic tests. If we want to perform the normal precision test on an in vivo device, we would need to insert multiple devices in the same person. This would introduce the question of the glucose being the same at every spot in the body. The best that the CGM manufacturers have been able to do is to place two CGM devices in the same person and compare the results from the two sensors for precision. Because both devices are in the same person, they should read the same glucose level. This in vivo precision measurement is not the same as the in vitro measurement. The in vivo measurement can produce thousands of paired points from one subject, but are the data points independent because they are coming from the same person The precision data from the three manufacturers are shown in Table 5.7. 

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