Chest

Chest

Volume 120, Issue 5, November 2001, Pages 1651-1654
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Laboratory and Animal Investigations
Use of Glass Capillaries Avoids the Time Changes in High Blood Po2 Observed With Plastic Syringes

https://doi.org/10.1378/chest.120.5.1651Get rights and content

Study objectives

In adults, arterial blood samples are usually drawn using plastic syringes. In contrast to glass syringes, plastic syringes let oxygen diffuse through their wall. This results in Po2 changes during storage, especially when Po2 is high. An alternative to glass syringes is the Microsampler (Roche Diagnostics; Schaffhausen, Switzerland), a commercially available device consisting of a heparinized glass capillary fitted with a 26-gauge needle and used to collect arterial blood in the same way as a plastic syringe fitted with a needle.

Design

We evaluated the performance of the Roche Microsampler for storing arterial blood in view of Po2 measurement, comparatively with glass and plastic syringes. Five approximate initial Po2 levels (650, 400, 200, 130, and 80 mm Hg) and two storage temperatures (ambient temperature and 4°C) were studied.

Settings

Bench study.

Results

Plastic syringes allowed reliable measurement of Po2 values when initial Po2 was too low to ensure complete hemoglobin oxygen saturation, but were associated with time-dependent underestimation of Po2 at higher initial Po2 values. No such underestimation occurred with the Roche Microsampler stored at 4°C for up to 1 h for all Po2 levels studied.

Conclusion

The Roche Microsamplers appeared to be reliable devices in preventing oxygen diffusion.

Section snippets

Materials

The Roche Microsampler, which was designed in the early 1980s,45 consists of two glass capillaries containing lithium heparinate, mounted in series, and fitted with a 26-gauge needle via a short polyethylene connector. A schematic diagram is presented in Figure 1. Total capacity is 240 μL. The glass capillaries fill readily after puncture of the arterial wall by the needle; the rapid, pulsing rise of blood in the capillaries shows that a vein has not been punctured by mistake. We compared the

Results

Figure 2 illustrates Po2 changes over time at ambient temperature. With Po2 at 650 mm Hg, a sharp fall in Po2 (approximately 150 mm Hg at 60 min) was noted in the plastic syringes and a considerably smaller decline (approximately 60 mm Hg) was noted in the glass syringes and Roche Microsamplers. With Po2 at 400 mm Hg, the Po2 fall was also larger in the plastic syringes (approximately 90 mm Hg at 60 min) than in the glass syringes and Roche Microsamplers (approximately 40 mm Hg at 60 min). With

Discussion

Preheparinized plastic syringes are the devices most commonly used to store blood for blood gas analysis. It has been demonstrated repeatedly that a major drawback of plastic syringes is oxygen diffusion through the syringe wall when Po2 in the blood is high.123 Although glass is impermeable to oxygen,1 glass syringes are no longer used because they require manual heparinization and, above all, they are not disposable.

Heparinized capillaries are commonly used to collect blood samples, usually

Acknowledgment

We thank Drs. J-F Mollard and A. St John of Roche Diagnostics (formerly AVL Medical Instruments) for their advice and for providing the Roche Microsampler devices used in this study.

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There are more references available in the full text version of this article.

Cited by (0)

This study was supported by a grant from Roche Diagnostics.

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Copyright © 2001 The American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.