EXTERNAL QUALITY ASSESSMENT Evaluating pO2 accuracy


using commutable EQA materials: a 20-year review


Arterial blood gas analysis is an important part of the diagnosis and management of several health conditions, and is increasingly conducted at the point of care. With EQA paramount for such devices, Ceri Parfitt and Annette Thomas present a retrospective study examining the performance of laboratory and POC analysers.


Arterial blood gas (ABG) analysis is an essential component of assessment of critically and acutely ill patients in emergency departments and in intensive care units.1


Many wards and


outpatient departments also use blood gas analysers in providing care to their


patients, such as those with respiratory disease. ABG analysers provide a rapid assessment of patient oxygenation, acid-base balance and metabolic status, through measurement of partial pressure of oxygen (pO2 (pCO2


) and carbon dioxide ), hydrogen ion and bicarbonate


concentrations. As a result, conditions such as sepsis, respiratory failure and diabetic ketoacidosis can be quickly diagnosed and treated.


Blood gas analysis The earliest blood gas analysers, developed in the 1950s were able to measure a limited number of analytes, including pH, pCO2


and pO2 . These


Blood gas analysers are now routinely found in intensive care units, emergency departments and even ambulances.


2


devices, typically located in central hospital laboratories were large and complex, requiring trained laboratory staff to operate, as well as extensive sample handling time. As advances in microprocessor technology and miniaturisation of components progressed in the late 20th Century, analysers became more compact and easier to use, with an expanding testing repertoire, including electrolytes, glucose, lactate and haemoglobin. However, most analysers remained in laboratories, with relatively lengthy turnaround times. In recent years, rapid development within the point-of-care testing (POCT) market has led to dramatic improvements in access to blood gas analysers, which are now routinely found in intensive care units, emergency departments and even ambulances. Innovations include smaller sample volume requirements and rapid turnaround time (<2 minutes); as well as improved user interfaces, allowing use


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