The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

NEW SMALL VOLUME ARTERIAL BLOOD SAMPLER WITH UNIQUE MIXING CAPABILITIES.

Michael Vester and Peter Brondum, Radiometer Medical A/S, Copenhagen, Denmark.

Background: Inadequate mixing of settled samples is a common and often overlooked preanalytical error that may severely bias measuring results. Inhomogeneity of samples is impossible to detect visually due to the strong coloration of hemoglobin and thus is often not recognized. In designing the new arterial blood sampler, PICO^{TM}70 (Radiometer Medical A/S), an important aim was to construct a sampler that would combine a small sample volume with optimal mixing capabilities. This aim was reached with an optimized barrel diameter (D) and the use of a heparin disc working as a stirring device. Materials and Methods: The PICO^{TM}70 (D=7 mm) was compared with three 1 mL tuberculin samplers (D=4 mm)(Smooth-E Radiometer, Rapidlyte Chiron (Manufactured by Marquest Medical Products Inc), Pro Vent Concord), a 3 mL sampler (D=9 mm, Smooth-E Radiometer), and a capillary device (D=1 mm, Microsampler AVL) with respect to mixing capabilities. The test was carried out as a worst case situation with 1 mL of fully settled and cooled (4 °C) blood in each sampler (2 mL in the 3 mL sampler and 220 µL in the capillary device). Mixing was performed by the recommended combination of a rotator and rolling between the palms. After a total mixing time of 20, 40, 60, 120, and 180 seconds the ctHb was measured on an OSM^{TM}3 on samples from the top (0.9 mL mark) and from the bottom of the sampler (0.3 mL mark). 120 samplers were tested. Results: The mean difference between ctHb measurements at the bottom and at the top of the samplers was calculated for each mixing time and set as an expression of homogeneity of the sample (Figure). As seen the PICO^{TM}70 has mixing capabilities that are only matched by those of a 3 mL sampler. Presumably the heparin disc is working as a stirring device thus compensating for the small barrel diameter of the PICO^{TM}70. All tuberculin samplers show poor mixing capabilities as a direct consequence of the small diameter. The capillary device included in the test proved impossible to mix. Conclusion: PICO^{TM}70 has an optimal construction that combines the possibility of a small sample volume (0.3 mL - 1.5 mL) with mixing capabilities similar to those of a 3 mL syringe.

Mixing Characteristics (See original for figure)

OF-97-145

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