No abstract

The venous values of pH, corrected for bias, can give arterial values which are within reasonable laboratory and clinical acceptance criteria. For PCO2 this is also true, except for peripheral blood, where the standard deviation is outside laboratory acceptance criteria but within clinical acceptance criteria. For PO2 the arteriovenous differences are not randomly distributed and even for PO2

Arterial pH and Pco(2) can be calculated precisely from peripheral venous blood in a broad patient population. The method has potential for use as a screening tool in emergency medical departments and in medical and surgical wards to assess a patient's acid-base and oxygenation status prior to sampling arterial blood or to help in the decision to refer the patient to the ICU. In departments where arterial blood gas values are used to monitor patients (eg, pulmonary medicine), the method might reduce the number of arterial samples taken by replacing them with peripheral venous blood samples, thus reducing the need for painful arterial punctures.

The aim of the present study was to evaluate a method for calculating arterial values of pH, carbon dioxide tension (PCO 2 ) and oxygen tension (PO 2 ) 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, PCO 2 and PO 2 were compared.Measured and calculated values of pH and PCO 2 correlated well, with the difference between them having a very small bias and standard deviation (pH -0.001¡0.013, PCO 2 -0.09¡0.28 kPa) within those considered acceptable for laboratory equipment and clinical practice. All but four patients had peripheral oxygen saturation (Sp,O 2 ) f96%, and for these measured and calculated PO 2 correlated well, with a difference such that the bias and standard deviation suggested that calculated PO 2 may be clinically useful (PO 2 0.11¡0.53 kPa).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.