In arterial line management, where should the transducer be zeroed to ensure accurate pressure readings?

• A. Zero at the level of the left atrium.
• B. Zero at the level of the aorta.
• C. Zero at the level of the right atrium (phlebostatic axis).
• D. Zero at the level of the heart apex.

Answer: (C)

Zeroing at the level of the right atrium, using the phlebostatic axis, establishes the transducer’s reference where the central venous pressure would be measured. Because hydrostatic pressure changes with vertical height, aligning the transducer to the RA level removes position-related reading differences and yields true arterial pressures. The phlebostatic axis sits roughly at the fourth intercostal space at the midaxillary line, approximating the RA. Zeroing here avoids errors that would occur if the reference were at the left atrium, the aorta, or the heart apex.