The Value of Capillary Blood Gas Measurement in the Intensive Care Unit

Arterial blood gas ( ABG ) sampling represents the gold standard for determining the patients’ acid-base and ventilatory status. However, it has many drawbacks. This study assessed the relationship and agreement between arterial and capillary measurements in adult intensive care unit ( ICU ) patients. ABG and capillary blood gas (CBG) samples were obtained from 49 adult and 51 elderly ( a total of 100 ) patients with cardiopulmonary disorder, cerebrovascular accident, intoxication, multiple trauma, and metabolic coma. All samples, collected at the same time, were analyzed. The kendall’s tau rank correlation, unpaired t-test, paired-t test and Bland-Altman method which is used for measure ment of agreement, were used for analysis. The median age was 65 years ( min: 18, max: 90 ). There was a significant correlation between ABG and CBG values of pH, PCO 2 , and HCO 3 ( P < 0.001 ). The agreement between measurements of pH, PCO 2 , and HCO 3 in ABG and CBG was good with mean differences of 0.0085, 3.049 mmHg, and 1.268 mmol / L, respectively. Despite a statistically significant correlation between arterial and capillary PO 2 ( P < 0.001 ), the agreement between capillary and arterial measurements of PO 2 was poor ( mean difference: 16.52, 95% CI: -23.74 to 56.79 ). Blood pressure and body temperature did not alter the correlations and agreement between measurements in elderly and adult groups and all together ICU patients. Capillary blood samplings provide an accurate assessment of pH, PCO2, and HCO3 and can be used to reliably measure the acid-base and ventilatory status of patients in the presence of any limitation of or contraindication to ABG in ICU.