Comparison of electronic and manometric central venous pressures. Influence of access route

Manometric central venous pressure (CVP) measurements are still routinely used as indicators of intravascular volume, particularly during surgery and when cardiorespiratory function is assumed to be normal. The difference between manometric measurements of CVP, from a 16-gauge polyvinylchloride catheter, and those obtained electronically from the level of the right atrium through the proximal port of a pulmonary artery catheter was studied in 40 patients admitted to the ICU. Despite correct position of the catheter tips and adequate respiratory oscillations, manometric measurements differed considerably from right atrial mean pressure determinations. The discrepancy was largest and the direction of change not predictable when the CVP catheters was inserted via an antecubital or right subclavian vein. When catheters were inserted from the left subclavian vein or the internal jugular, on the other hand, manometric CVP was consistently 4-6 cm H2O higher than the electronic pressure determination. If a manometric CVP catheter is to be used, the internal jugular or left subclavian routes appear preferable.