Pneumatic transport exacerbates interference of room air contamination in blood gas samples

J. Rex Astles, David Lubarsky, Bounthon Loun, Frank A. Sedor, John G. Toffaletti

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Objective. - To characterize and control the potential interference to PO2 determinations when blood contaminated with air is sent via a pneumatic tube system (PTS). Design. - Both tonometered blood at PO2s of 65, 75, 142, and 339 mm Hg and arterial blood gas samples from patients with baseline PO2s from 70 to 400 mm Hg were analyzed for PO2 to determine possible effects of air contamination from PTS transport. Setting. - A large teaching hospital in which a variety of personnel routinely send samples to the laboratory by PTS transport. Patients. - Twenty patients under anesthesia for elective surgery and 21 patients in an intensive care unit who had a wide range of PO2s. Several additional patients with a preexisting lung pathology likely to cause hypoxemia were selected to provide samples with low PO2s. Main Outcome Measures. - Measurement of bias in PO2 between samples sent via PTS and samples walked to the laboratory. Results. - Interference from air contamination was worse after PTS transport compared with manual transport of the specimen. Over a wide range, the PO2 in specimens after PTS transport tended toward 160 mm Hg. Samples from hypoxemic patients were prone to errors in PO2 that could have resulted in clinical misinterpretation; 5 of 10 samples with a baseline PO2 less than 85 mm Hg had increases of 10 mm Hg or more when contaminated with air. Cooling samples with high PO2s minimized changes to PO2, probably by increasing the solubility of oxygen. Mechanical buffering by various liners used in the carriers did little to alleviate the interference. Decreasing the speed of pneumatic transport by 50% lessened the effect on PO2. Conclusion. - Interference can be minimized by carefully purging samples of all air bubbles using the following protocol: invert syringe to check for air bubbles, then retap and reexpel bubbles if necessary. Personnel that collect and send blood gas samples via PTS should be educated about the problem of interference. Modifications both to pneumatic sample transport systems and to blood gas syringes should be investigated to minimize the effect.

Original languageEnglish (US)
Pages (from-to)642-647
Number of pages6
JournalArchives of Pathology and Laboratory Medicine
Issue number7
StatePublished - Jul 1 1996

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Medical Laboratory Technology


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