Chest
Clinical InvestigationsVariability of Arterial Blood Gas Values in Stable Patients in the ICU
Section snippets
Patient Selection
The study group consisted of 29 consecutive patients in the intensive care units of Harborview Medical Center who were judged by their physicians to be clinically stable and who were able to give informed consent (patient or family member) for the study. Descriptive data are provided in Table 1. Patients were accepted for the study if within the preceding four hours systolic blood pressure varied by less than 10 percent, temperature varied by less than 0.5°C, and mental status remained
ABG Variability
Arterial oxygen saturation exceeded 94 percent in all patients (FIo2 = 0.5). Mean PaO2, PaCO2 and pH values across patients ranged from 71.6 to 257.7 mm Hg, from 24.4 to 73.5 mm Hg, and from 7.36 to 7.56 units, respectively (Tables 2 and 3). The intra-patient ranges (highest value obtained over six samplings minus lowest value) in PaO2, PaCO2 and pH extended from 1 to 45 mm Hg, from 1 to 8 mm Hg, and from 0.01 to 0.08 units respectively. (Corresponding mean ± SD: PaO2, 16.2±10.9 mm Hg; PaCO2,
DISCUSSION
In initiating this study it was our concern that, in the intensive care setting, altered ABG values alone often prompt clinicians to make important therapeutic decisions, even without additional evidence for clinical change. In part, this practice results from a lack of knowledge of the range of fluctuation around the mean ABG value that can occur in seriously ill but stable patients.
These data provide an indication of the spontaneous variation observed over brief intervals in such subjects.
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Supported in part by NIH Grant No. HL00248.
Manuscript received August 9; revision accepted February 1.