Blood gas analysis: POCT versus central laboratory on samples sent by a pneumatic tube system.

ABSTRACT

BACKGROUND: We aimed to compare the results of blood gas analyses, performed at point-of-care and in the central laboratory (CL), on samples sent via a pneumatic tube system (PTS). METHOD: Specimens from two locations (lung function laboratory (LFL) and pneumology wards) were first analysed locally and then sent to the CL via PTS. RESULTS: While none of the blood gas samples from the LFL had air bubbles, 21 samples from the wards (n=31) had air bubbles in them. The mean time difference between the first (POCT) and the second (CL) determinations from LFL was 13.3+/-5.4 min (n=27) and from the wards 20.2+/-11 min. For pO2 the differences between LFL and CL results, for patients undergoing a 100% O2 test, were unacceptably large. For pO2 range 41-407 mm Hg, the difference was -2.4+/-3.2 (n=25). For the samples from the wards, the difference in pO2 between ward (range 37-183 mm Hg) and CL was -13+/-18 mm Hg. CONCLUSION: Irrespective of air bubbles, the transport by PTS has very little or no effect on pH and pCO2. If air bubbles cannot be excluded with certainty, PTS is not an appropriate transport medium for measurement of pO2 on blood gas samples.