Deidra Huckabee MSN, RN, CCRN

Research QuestionMedical ICU staff inquired about the

accuracy of utilizing the bedside Point of Care Testing (POCT) analyzer and standard laboratory analysis of samples transported via Pneumatic tube system

Rationale

POCT assessment of arterial blood gases is an increasingly common method of measurement for guiding ventilator management in ICU’s.

RationaleThe team observed discrepancies in

PaO2 values between our POCT analyzer (the i-Stat) and blood gas specimens transported to our laboratory via the pneumatic tube system (PTS).

RationaleThe purpose of this study was to

determine accuracy of PaO2 values obtained via:

POCT analyzerPTS systemHand delivery to the laboratory

MethodsThe project took place in the

Medical ICU in 2 stages

Stage 1 12 patient blood gases were analyzed

per bedside i-Stat and by a blood specimen to be tested in the lab.

MethodsStage 1 12 patient blood gases were analyzed per

bedside i-Stat and by a blood specimen to be tested in the lab.

After evaluation 8 of the 12 specimens has PaO2 difference great than 10mmHg

This was considered clinically significant and moved the analysis into the next stage

MethodStage 2

18 samples were drawn from different patients with three different types of testing:

Bedside i-StatSending blood gas to the labWalking blood gas to the lab

Results

The results were obtained via a two-sided, dependent paired t-test

The largest variation in PaO2 results was found between samples sent via PTS versus POCT and specimens walked to the laboratory.

ResultsThe mean difference between POCT

analysis and samples sent via PTS was 18.4 mm Hg (95% Cl 9.4-27.4mmHg)

The mean difference between walked samples and PTS samples was 9.7 mmHg ( 95% Cl 5.9-13.5 mmHg)

ResultsThe results were obtained via a two-sided,

dependent paired t-test

The specimens that were tested at the bedside using an i-Stat monitor and the specimen walked to the lab had similar PaO2 results.

The specimen sent through PTS has consistent higher PaO2 results than the other 2 methods

Conclusion

Arterial blood gas samples sent via PTS have more PaO2 variability in PaO2 results than samples tested using POCT or walked to the lab.

Why?May be due to air bubbles which are

mixed in the sample when transported via PTS

This theory is also supported by the observation of consistently lower PaO2 values obtained via POCT which might avoid the introduction of microscopic air resulting from transport

Change in Practice

MUHA now has a policy in place for all ICU’s to tube blood gas testing via POCT or walk them to the lab to obtain the most accurate results.