Abstract
Background:
Specimen transport is a pre-analytical factor that can influence the accuracy of blood gas results as gas exchange can occur between an air bubble and the sample. A literature review determined that there is no uniform consensus as to whether pneumatic tube transport is appropriate for blood gas specimens. Our study was designed to determine acceptability of pH, PCO2 and PO2 results for specimens transported via a pneumatic tube
Methods:
Blood gas measurements were conducted on performance comparable Siemens Rapidpoint 500 analyzers. Blood gas samples were analyzed at point-of-care then sent through the pneumatic tube system for repeat analysis. Sample integrity was evaluated prior to tube transport. All sample analysis was performed by two experienced respiratory therapists. All point of care testing was performed by one therapist and the second therapist performed the post tube transport analysis. CLIA/CAP total allowable error limits were utilized to establish acceptable limits for pH, PCO2, and PO2. Phase two testing introduced a rubber stopper and immobilization padding prior to specimen tube transport.
Results:
Sixty blood gas specimens were analyzed pre and post-tube transport. 96.7% of pH results, 88.3% of PCO2 results, and 50.0% of PO2 results were within the acceptable range. The average biases between pre and post pneumatic tube specimens were -0.0048 for pH, 1.25 mm Hg for PCO2, and 0.99 mm Hg for PO2. In phase two, 54 blood gas samples were measured pre- and post-tube transport utilizing the mitigation interventions, 74.1% of PO2 results (average bias of -0.59 mm Hg). 92.6% of PCO2 results and 100% of pH measurements were within acceptable limits. To determine the clinical significance of the PO2 differences, data with PO2 values outside of the reference interval (70–100 mm Hg) with the potential to impact patient management were examined. Ten specimens were <70.0 mm Hg pre-transport, all of which had a higher post transport PO2 (average increase of 7.4 mm Hg). Importantly, 100% of these specimens remained at < 70.0 mm Hg PO2 post transport. All samples within the normal reference range remained in range post transport. The largest variation occurred in samples with high PO2 values.
Conclusions:
The study confirmed measurable variation in PO2 values post tube transport. The PO2 variability was reduced to an acceptable level by immobilizing the sample and capping the syringe with a rubber stopper. Findings support tube transport of blood gas specimens under these conditions.
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