Copyright ©ERS Journals Ltd 2009 Converting venous acid–base and oxygen status to arterial in patients with lung disease1 Center for Model Based Medical Decision Support Systems, Dept of Health Science and Technology, Aalborg University, 2 Dept of Respiratory Diseases, Aalborg Hospital, 3 Dept of Anaesthesia and Intensive Care, Aalborg Hospital, and 4 Dept of Clinical Biochemistry, Centre of Cardiovascular research, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark. CORRESPONDENCE: S. E. Rees, Center for Model Based Medical Decision Support, Aalborg University, DK-9220 Aalborg, Denmark. Fax: 45 98154008. E-mail: sr{at}hst.aau.dk Keywords: Acid–base chemistry, blood gas analysis, oxygen saturation
Received: September 12, 2008
The aim of the present study was to evaluate a method for calculating arterial values of pH, carbon dioxide tension (PCO2) and oxygen tension (PO2) from peripheral venous values.
In total, 40 patients were studied. Arterial and peripheral venous blood were sampled at a department of respiratory diseases. Arterial values were calculated from venous, and measured and calculated values of arterial pH, PCO2 and PO2 were compared.
Measured and calculated values of pH and PCO2 correlated well, with the difference between them having a very small bias and standard deviation (pH -0.001±0.013, PCO2 -0.09±0.28 kPa) within those considered acceptable for laboratory equipment and clinical practice. All but four patients had peripheral oxygen saturation (Sp,O2)
The present study evaluates a method for calculating arterial pH, carbon dioxide tension and oxygen tension from venous blood. It has been shown that arterial pH and carbon dioxide tension can be calculated precisely, and that oxygen tension can be calculated with reasonable precision in the vast majority of patients. This method might be useful in reducing the need for painful arterial punctures.
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