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Point-of-Care Blood Gas Analysis
Industry Insight

Point-of-Care Blood Gas Analysis

Point-of-Care Blood Gas Analysis
Industry Insight

Point-of-Care Blood Gas Analysis

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Blood gas analysis is an important measurement in critical care patients. Delivering this testing at the point-of-care offers a number of advantages to both the patient and nursing team. Sphere Medical recently introduced Proxima, a miniature in-line blood gas analyser, at the Intensive Care Society meeting in London.

We spoke to Gavin Troughton, VP Business Development, Sphere Medical, to learn more about Proxima, and the features that make it well suited to use in the critical care environment.

AM: Can you tell us a little about the Proxima miniature in-line blood gas analyser?

GT: Proxima is an innovative miniature in-line blood gas analyser (BGA) that supports rapid and frequent blood gas measurements at critical times. Uniquely, the new Proxima system developed by Sphere Medical (Cambridge, UK), enables blood gas testing to be delivered directly at a patient’s bedside.

The CE marked Proxima System incorporates a dedicated bedside monitor, as well as a disposable Proxima Sensor integrated into the patient’s arterial line. The sensor contains a range of biological sensors and sits in series in the arterial line, with the blood pressure transducer. When an arterial blood gas analysis is required, blood is withdrawn from the patient directly into the Proxima Sensor and a panel of analytes is measured. All blood is returned to the patient avoiding any blood loss. The disposable sensor can be used for monitoring blood gases and electrolytes over a 72 hour period as many times as required.

Proven to measure to laboratory analyser accuracy, results are rapidly displayed on the bedside monitor and can be electronically transferred for permanent record. The system also carries out all quality control checks that would be undertaken on a traditional blood gas analyser to ensure validity of test results. It also includes a facility to be challenged with liquid controls.

The best way to understand how Proxima works is by having a look at the following video:

The new Proxima represents the next step on in Point of Care testing (POCT) as it is actually attached directly to the patient through their arterial line, meaning that for the first time blood gas results can be delivered, like blood pressure results, within the patient’s bed space.   

AM: Which design features make the Proxima well suited for the critical care environment?

GT: Proxima operates as a closed system dedicated to use on a single patient. The operating model has been designed specifically to fit into and simplify the workflow and current practices of the critical care environment and to address the needs of critical care patients. 

1. Nursing dependency:  The shift to blood gas analysis being carried out in the near patient environment has put additional work onto the critical care staff and takes them away from the patient at critical times. Having rapid blood gas measurements directly within the bed space means that a nurse can actually continue to look after the patient whilst undertaking these important measurements. 

The benefits of immediate access to frequent blood gas analysis are clear when there is the potential for rapid and life-threatening changes to blood gas chemistry, such as during major cardio, neuro and vascular surgery. Likewise, the critically ill patient, during septic shock or sepsis, or patients with severe hypoxic respiratory failure (SHRF) would certainly benefit from frequent blood gas monitoring. 

The Proxima Sensor, a miniaturised, sterile and biocompatible version of a BGA, is integrated into the patient’s arterial line which enables each patient to have their own BGA. Blood can then be drawn directly into the device to give immediate and more frequent blood gas measurements without leaving the patient.

2. Blood conservation:  There is a high incidence of anaemia in critical care, with blood sampling being a major contributing factor. Due to the fact that it is in-line, the Proxima System enables closed blood sampling. When a blood gas analysis is required, blood is simply withdrawn from the patient directly into the Proxima Sensor  and once analysis is completed, all blood is returned to the patient. This reduces the risk of hospital acquired anaemia and consequent transfusions which are both expensive and carry a risk of adverse reaction. This is particularly important in a critical care environment where blood gases are an extremely widely used measurement and is the most commonly undertaken blood test in ICU and operating theatre settings.

3. Infection control: Any draw of arterial blood requires stringent infection control techniques to avoid the possibility of introduction of a bloodstream infection, which is associated with high mortality rates and increased cost of care, as well as avoiding blood-splash injury to care givers from e.g. hepatitis infection. 

By operating as a closed system, Proxima keeps infection control simple and effective. Furthermore, many patients in critical care require isolation for infection control reasons – either they have a highly contagious condition such as norovirus, or have very low immunity due to disease or chemotherapy treatment. Proxima avoids the transfer of blood samples around the unit to a central point (the blood gas analyser) which can be a vector in the transmission of infection.

AM: How does the Proxima compare to bench top analysis? 

GT: The Proxima system uses proven sensing methods for determining analyte concentrations in patient blood samples, each a miniaturised version of the electrochemical sensors used in a traditional blood gas analyser.

A recent observational method comparison study at Queen Elizabeth Hospital, Birmingham, UK, demonstrated excellent agreement between Proxima and the standard bench top blood gas analysers. During the course of the study over 300 comparative measurements were taken across the system’s analyte range of pH, pCO2, pO2, haematocrit and K+, with each analyte showing excellent agreement with the reference bench top blood gas analyser (Roche Cobas b221).

Dr Tom Clutton-Brock, Senior Lecturer Anaesthesia and Intensive Care Medicine, University Hospital Birmingham and Chief Investigator for the study, commented, “The main aim of this study has been to determine whether Proxima gives the same clinical results as the reference bench top blood gas analyser when it is used on patients in a clinical environment. The answer is unequivocally yes. Just as importantly, the staff using the system really appreciated how simple it was to take a measurement with Proxima. We are really excited about the impact that this could have on management of sick and unstable patients.”

AM: What has feedback from users in the clinical setting been like?

GT: Proxima has been fully evaluated and validated in a clinical setting recently at Queen Elizabeth Hospital, Birmingham, UK. Use of the Proxima system was carried out by the clinical staff at the Queen Elizabeth Hospital who each underwent an initial 90 minute training programme.  

The feedback from the clinical staff using Proxima was that considering that this is a completely new device, with some training and familiarisation with the product, the system is easy to use, especially because the monitor guides you through every step of the process. 

Previously, as part of the CE mark completion; a usability study with the Proxima System was completed at the Queen Elizabeth Hospital, Birmingham, UK. Anaesthetists, ICU nurses and Operating Department Practitioners were trained on the use of the Proxima System before being assessed on the ability to operate the Proxima System in a simulated clinical environment. The majority of clinical staff rated the Proxima System as easy to use.

At the recent AAGBI 2014 Annual Congress, Dr. Tom Clutton-Brock, Senior Lecturer Anaesthesia and Intensive Care Medicine, University Hospital Birmingham, presented in an industry seminar discussing ‘True Point-of-Care Testing’. The seminar considered the challenges of maintaining control of patient physiology in the ICU. The presentation is available to view at: http://www.spheremedical.com/content/clinical-resources

Sphere Medical will be exhibiting the Proxima system from 17 to 20th March at the ISICEM 2015 meeting in Brussels. 

For further information on the product, please visit www.spheremedical.com or if you have a direct request send it to proxima@spheremedical.com