Effect of Pneumatic Tube Transport on Blood Gases and Supplemental Analytes

Abstract

Background: Pneumatic tube transport of blood gas samples is a common method of delivery to a blood gas laboratory. Prior studies have shown acceptable performance for pH and PCO2, but results for PO2 vary based on the study, with the consensus being latent air bubbles or non-pressure sealed pneumatic tube carriers as the culprit. What is typically unaccounted for in these studies are the other analytes often measured by blood gas laboratories (e.g. electrolytes, metabolites and oximetry) even though studies exist highlighting a potential for hemolysis in samples sent via tube to core laboratories. Many other studies also only include a single pathway through the pneumatic tube system, for example, from the emergency department or OR to the blood gas lab. This study evaluates blood gas values and the concomitant analytes generally reported through the full scope of a 500 + bed academic medical center across multiple pneumatic tube stations. The aim of the study was to determine the effect of pneumatic tube transport (SwissLog) on all reported values from our blood gas analyzers (Radiometer 835). Methods: The study was conducted by the blood gas laboratory at the University of Utah Hospital. Blood samples were received through normal care processes. A split sample comparison was performed on left over blood after patient results were reported. IRB approval is not required for this QA project. In eight cases the remaining sample size was large enough to split immediately. In forty-six cases the samples were pooled, tonometered for 20 minutes, then split. Once a sample was split into two separate syringes both were walked to a pneumatic tube station where one sample was tubed and the other was re-walked back to blood gas lab. After both samples had returned to the blood gas lab they were analyzed serially on the same blood gas analyzer. Two samples were sent from each of 27 different pneumatic tube stations throughout the hospital. Results were graphed on a difference plot with upper and lower control limits set to conform to acceptable CLIA tolerances. Results: Average bias for each analyte is neither clinically or statistically significant. Two data points for tHb fell outside defined tolerance. Each outlier is surrounded by similar data points that were in-range and the difference isn’t clinically significant. Conclusions: Pneumatic tube transport of blood gas specimens is acceptable for blood gas parameters and supplementary analytes.