Jeffrey M. Haynes, RRT, RPFT, FAARC
Blood gas quality control (QC) is an essential and mandatory part of a laboratory’s quality plan. The QC range should be 2 standard deviations (SD) from the mean value. Two SD is the recommended range because the empirical rule states that if the blood gas analyzer is operating normally, and the QC material is untainted, 95% of all QC results should be within 2 SD of the mean. In other words, a QC value 2 SD from the mean should only occur once in 20 measurements (5%).
The empirical rule also states that 99.7% of QC results should be within 3 SD of the mean. In other words, a QC value more than 3 SD from the mean should never occur if the analyzer is operating normally.
If a QC test is outside of 2 SD (Westgard 12S violation), a “warning” condition is present, and the analyzer should be inspected for problems. If a repeat QC test is also outside of 2 SD (Westgard 22S violation), the device should be taken out of service. (Remember, a value 2 SD outside of the mean should only happen 5% of the time). If a QC test is outside 3 SD (Westgard 13S violation), the QC test fails and the device must be taken out of service. The corrective action must be documented and the analyzer can only be placed back into service when the problem is resolved.
Many blood gas analyzers utilize assayed QC material. Assayed QC material has manufacturer-provided ranges, whereas unassayed QC materials require the user to calculate the mean and ranges from 20+ measurements. However, the use of assayed QC material does not remove the
responsibility of the laboratory to calculate the mean and ranges of QC measurements. The laboratory must make these calculations to verify that the manufacturer-provided QC ranges are valid. Validating assayed QC ranges is a Clinical Laboratory Improvement Amendment (CLIA) requirement: “the laboratory may use the stated value of a commercially assayed control material provided the stated value is for the methodology and instrumentation employed by the laboratory and is verified by the laboratory.”
If the manufacturer-provided QC ranges do not represent the true performance of the analyzer, QC testing may not alert the laboratory’s clinicians that a problem exists. Such a situation may affect the accuracy of patient data and potentially affect patient care.
Figure 1 shows a Levey-Jennings plot from a malfunctioning analyzer that remains within the manufacturer-provided ranges but is outside of the measured 2 SD range.
Recently, the QC lots in our laboratory changed. Setting up the new QC lots requires scanning bar codes, which populate the software with the manufacturer-provided QC ranges, However, the mean value and ranges can be adjusted.
Figure 2 shows the measured mean and 2 SD range vs. the manufacturer-provided ranges.
In addition, I calculated the true SD of the manufacturer-provided ranges. The measured mean agreed with the manufacturer-provided mean. However, the manufacturer-provided ranges were very wide. The manufacturer-provided ranges were particularly wide for hemoximetry, ranging from 12.5 to 75 SD from the mean.
Figure 3 shows a Levey-Jennings plot of PO2 QC testing; the manufacturer-provided ranges were more than 9 SD from the mean.
Verifying assayed QC ranges is a CLIA requirement for good reason. Manufacturer-provided QC ranges may be much wider than 2 SD from the mean. As shown in Figure 3, a PO2 QC on our analyzer could be 9 SD away from the mean and the QC would still pass if the manufacturer-provided ranges were used.
Most, if not all, blood gas analyzers should provide the user with the measured mean and SD derived from QC testing. If you’re not sure how to verify and adjust your QC ranges, contact your manufacturer for assistance. QC range verification and adjustment need to be performed each time the QC lot changes.
Jennie Weltz Horpedahl, BSRT, RRT, RRT-NPS, RPFT, AE-C
Tri-cities Washington is located in the southeast corner of the state. Surrounded by fertile fields and lots of sage brush, this high desert community is home to approximately 300,000 residents. It is a wonderful place to live, but for residents diagnosed with ALS, the remote location of the Tri-cities and lack of specialty physician support can be a huge barrier to getting the specialized care and support needed to deal with their disease. Or at least it was until 2018.
It all started with one patient and her family.
When Pamela Foucault was diagnosed with ALS in 2013, the closest specialized, multidisciplinary clinic was located more than 150 miles away. Her family eventually relocated to be closer to specialty care, and after her death her husband began advocating for improved access to local resources for patients diagnosed with ALS.
Our lab got involved in late 2017 as part of an effort to develop a multidisciplinary ALS telehealth clinic in partnership with the Swedish Neuroscience Institute in Seattle. The Tri-cities clinic was modeled after their in-person clinic and includes two physicians who join a live in-person multidisciplinary team via telehealth computer stations. The multidisciplinary team includes representatives from physical therapy, occupational therapy, speech therapy, nursing, respiratory therapy, social work, palliative care, and the local ALS chapter.
The once-a-month clinic sees up to four patients each time, with each clinic lasting three hours. Groups of providers rotate through to each patient every 45 minutes. The multidisciplinary team meets 30 minutes prior to the start of the clinic to review that clinic’s patients and identify key concerns or issues to address. The team comes back together after the three hour clinic to share information and collaborate on unresolved issues for each patient.
The respiratory therapist from the pulmonary function laboratory is teamed up with the clinic’s neurologist and RN. Testing performed includes sitting and supine FVC measurements, MIP measurements, and cough peak flow measurements. Diagnostic measurements not only help to trend the patient’s respiratory status and qualify the patient for respiratory support devices, but also to guide conversations and decisions for other procedures, some of which may require anesthesia, such as feeding tube placement. The respiratory therapists get a chance to step outside their diagnostic role a bit to help provide education, coordination of respiratory support
equipment (cough assist, noninvasive ventilation, etc.), and when necessary, additional patient assessment, acting as the physician’s eyes and ears.
In preparation for the clinic our staff were fortunate to shadow the respiratory therapist at the Swedish clinic. It was very helpful to see not only the clinic’s flow, but to learn many tips and tricks to ensure we were prepared with the right equipment and the knowledge we would need to adapt to meet the patients’ needs. Their respiratory therapist, Janis, was a wealth of information, having worked with this patient population for a number of years, and she remains a valuable mentor.
Reflecting on our first year, we have had to overcome some road bumps and have certainly learned a lot, but we also have met some wonderful patients and families who are so grateful that they can stay close to home for their care. For me personally, it is nice to step outside the lab and connect with our patients in a different capacity.
As our region looks to increase the use of telehealth to bring additional services to our community, as well as provide support to surrounding areas, our lab looks forward to bringing our skills to support more patients and providers in the years to come.
Jennie Weltz Horpedahl, BSRT, RRT, RRT-NPS, RPFT, AE-C
This has been an interesting time here in Washington State and undoubtedly across the country. As I write this column in late March, I know my acute care colleagues will be on the frontline caring for these patients, and indeed, RTs across the mountains in the Seattle area already are. Over the last few weeks, as incidences of COVID-19 have increased across the country, it has been a challenge to keep up with new recommendations, changing guidelines, and the best way to keep ourselves and our patients safe.
As of today here in Washington, there have been 200 COVID-19-related deaths in the state and we are a few days into a statewide “Stay Home, Stay Healthy” initiative in which only essential businesses are operating in our communities. Similar initiatives have been rolled out in other states and communities, but what we are doing is all a little unique.
In the outpatient setting we were challenged to look at our processes, environment, and criteria for testing in the PFT lab. Some health systems have elected to suspend testing, while others remain open for essential testing and/or are still seeing patients as long as they screen out for COVID-19 exposure.
I think this is a wonderful opportunity for labs across the country to look at their practices and (hopefully) be ahead of the curve and have a game plan in place not only for this current crisis but future events as well. Based on our recent experience, here are ten things to consider:
Fast forward a few days from when I began to draft this article and cases of COVID-19 positive patients have continued to increase, along with caregiver and community anxiety. Hardly an hour goes by when I don’t hear someone discuss social distancing, hand hygiene, or the shortage of toilet paper at the grocery stores. It is truly a very interesting time. I am so proud of my respiratory colleagues, both inpatient and outpatient, who continue to show up and step up to provide the best patient care and adapt to the constant changes and updated recommendations to keep our community and patients safe.
I hope by the time this Bulletin is published this crisis will have passed or at least eased. Many of us here in Washington had little time to formulate a game plan for our outpatient labs. I do, however, take comfort that should another crisis arise we are better prepared to implement changes at a moment’s notice. From Washington — stay safe, stay healthy.
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