Manufacturers expand menus and point-of-care features to improve delivery of patient care.
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The results of a blood gas analysis, also known as arterial blood gas analysis, can provide physicians with much clinically valuable information and answer a host of questions about a patient’s condition. What is the patient’s respiratory status? How effectively are the lungs delivering oxygen to the blood? How efficiently are they eliminating carbon dioxide? If the patient is on oxygen therapy, is delivery at appropriate levels? How well are the lungs and kidneys functioning together? Does the patient require immediate treatment for an acid-base imbalance?
Patients presenting with difficulty breathing or shortness of breath will likely have blood gasses ordered, as will those with a history of respiratory distress or associated ailments, including trauma. The test will often be ordered during the initial workup and, particularly for patients on oxygen therapy or in critical care units, throughout treatment.
The test measures the concentrations of blood gasses, such as oxygen, carbon dioxide, and bicarbonate, as well as pH. Today’s analyzers can provide additional information, including values for hematocrit, hemoglobin, bilirubin, sulfur dioxide, electrolytes, glucose, lactate, and blood urea nitrogen.
Some of these results are calculated using sophisticated equations that take into account multiple factors, including pH, oxygen pressure, and levels of carbon dioxide and bicarbonate. Though the formulas are taught in medical school, today’s analyzers complete these calculations automatically, saving time and reducing the opportunity for human mathematical or transcription error.
Today’s instruments also act fast—a necessity for blood gas analysis. “Blood gas testing is different from all other clinical diagnostic tests. It is truly a critical care test. The test uses heparinized arterial whole blood for a sample, to prevent the sample from clotting, and requires a physician, respiratory therapist, or nurse draw the sample. It must be run within 15 minutes from the time of collection,” summarizes Larry Healy, marketing manager of Blood Gas Product at Roche Diagnostics Corp, Indianapolis. This presents challenges because neither speed nor quality can be compromised.
Because the test requires an arterial blood sample, the blood draw is more painful than that for more commonly ordered tests requiring venipuncture, but blood gas analysis also offers more information than less invasive options, such as pulse oximetry. Pulse oximetry, for instance, is limited to oxygenation information and does not address acid-base normality.
Different facilities develop different usage patterns as well as different testing structures. “Many hospitals use a combination of centralized and point-of-care testing. Point-of-care testing offers fast turnaround and gets the test result to the clinician quickly, but testing quality may suffer depending on how and by whom the test is performed. Testing in the central laboratory raises the likelihood that tests are run by the appropriately trained personnel and regulatory compliance is maintained,” says Heidi Egensperger, product manager for Clinical Instruments and IT at Radiometer America Inc, Westlake, Ohio.
How Much
Experts believe the frequency with which blood gasses are ordered in any facility is dependent on the local environment. Some facilities are more educated about the use of blood gasses than others, which can impact use of the test. Those more familiar with the results’ clinical value are likely to order the test more frequently.
Blood gasses are used most frequently in acute care situations, so testing is commonly seen in emergency departments, intensive care units, and surgical units. Egensperger estimates that “a large critical facility may run as many as 1,000 blood gasses per day.”
“Emergency room volumes will vary based on caseload and case type on a given day. What is important to the operator and supervisor is the capacity of the analyzer to handle any given sample load and the confidence that the analyzer is always ready to run a sample,” Healy says.
Even so, the use of blood gas analysis may be restricted when providers are less comfortable ordering what can be an uncomfortable test. Samples for blood gas analysis are typically drawn from a radial artery in the wrist, which is more painful and time-consuming than the more common venipuncture. Specimens from elderly patients or those who undergo frequent testing (such as diabetics) may be more difficult to gather since physical changes can occur in the arteries that can result in hardening of the walls, restriction of the lumens, and/or rolling vessels. Patients with arterial lines already in place, however, present few challenges.
By Whom
Typically, the sample is drawn by a respiratory therapist or a nurse. If the test will be run at or near the point of care, this same provider may run the sample as well. If the test is transported to a central laboratory, it will often be processed by a medical technologist.
“Minutes and seconds count in acute care. For the physician to make a diagnosis and initiate treatment, he or she must have the test results. Obviously, in acute care situations, the sooner those results are available the better,” Egensperger says.
“Depending on the hospital’s testing model, the test itself may be run on an analyzer located in a central lab or on a point-of-care analyzer located in or near the clinical department. Point-of-care testing may be performed by a clinician who is less skilled with the analyzer than a laboratorian,” he continues.
Analyzers are available for both models of care delivery, often from the same manufacturer. Some vendors will offer decentralized systems with integrative and remote control features. Software can enhance the operational efficiency of connected systems through features, such as screen sharing, that provide immediate real-time performance status, maintenance updates, and remote access for IT technical support 24/7.
Those intended for point-of-care testing often offer faster turnarounds and simpler use. Quicker results enable quicker action; trending information adds even more clinical value.
Ease-of-use features can include automatic specimen identification, mixing, and aspiration, as well as automatic quality control. “RT directors, lab managers, and POC coordinators [can] meet compliance requirements with centralized command and control of analyzer operation, documentation, and reporting. [Systems can] provide remote real-time monitoring of calibration data, QC, maintenance, and operator activity of all connected analyzers from one central location—without interrupting analyzer workflow,” Healy says.
Where and When
Despite the benefits, not all institutions rely solely on point-of-care testing to deliver blood gas results. “In many institutions, benchtop blood gas analyzers are used in the central laboratory to provide greater menu options and special applications, such as pleural fluid pH testing,” Healy says.
The addition of an application, such as pleural fluid testing, can bring added benefits in areas that include compliance and staffing. “It can help to simplify regulatory compliance by allowing the [pleural fluid] test to be run as a moderately complex test versus highly complex. This allows any qualified staff member in the lab to run the test, versus requiring a degreed supervisor who may not be available on late shifts,” Healy says.
Turnaround is fast. Many analyzers can run samples in 1 to 2 minutes. Turnaround from the sample draw to results delivery will vary with the institution and factors such as measured parameters, the analyzer and its location (ie, centralized or decentralized), and hospital processes. “The recommendation of various oversight organizations, such as The Joint Commission and CAP [College of American Pathologists], is 30 minutes,” Healy says.
Some vendors will assist organizations with evaluation of their workflow processes intended to find and create efficiencies that result in faster turnarounds, improved quality, and/or reduced costs. “A solution may include not just analyzers, but samplers and IT as well. Optimization of all testing phases—preanalytical, analytical, and postanalytical—will expedite turnaround,” Egensperger says.
Connectivity and integration can also help to improve turnaround, quality, and cost efficiency. Direct and middleware solutions exist to link blood gas analyzers with LIS and EMR systems.
New features enhance the usefulness of a system, from automated preanalytical and postanalytical steps to expanded menus. One system’s co-oximetry module measures both hemoglobin derivatives and bilirubin using spectrophotometry and an accepted mathematical algorithm to eliminate interference and inaccurate values. Acid-base map trending and patient trending of single-test parameters are also new. Previous advances have included the addition of electrolytes and hemoglobin derivatives measurement, digital elements, liquid calibration, and smart reagents.
Vendors are expected to continue to expand the clinical usefulness of their blood gas analyzers. “We would expect the next generation of analyzers to feature broader test menus, automation, ease of use, and smaller sample requirements, as well as features that help hospitals improve patient care while decreasing the need for analyzer ‘care and feeding,'” Egensperger says.
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Some of these advances will be expected to occur in instruments intended for use at or near the point of care. “Research and development is now incorporating advances to create a new-generation blood gas system that meets and exceeds the needs of the decentralized areas of the hospital to provide actionable information at the point of care,” Healy says.
As blood gas analyzers become more useful and more efficient, the results are also more useful—they are delivered more quickly and reveal more clinically valuable information. Diagnoses are made with greater speed and greater confidence. Appropriate treatments are started more quickly. Patient care and potential outcomes improve. Simply put: more questions are asked and answered.
Renee Diiulio is a contributing writer for CLP.
