arterial line positioning in relation to heart
- related: ICU intensive care unit
- tags: #literature #pulmonary
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In clinical practice, it is not uncommon to observe a discrepancy between BP measured by cuff and arterial line in critically ill patients. The transducer position is a critical determinant of all directly monitored intravascular pressures. The pressure transducer should be zeroed and leveled to a point that corresponds with the level of the heart. If the position of the patient relative to the transducer is changed, the level of the transducer should also be adjusted to avoid erroneous BP readings. The hydrostatic pressure difference between various vertical locations of the transducer is easily calculated (10 cm water height = 7.4 mm Hg), and subsequent transducer height adjustments will always produce these exact differences in measured pressures. When the arterial transducer is higher than the level of the heart, the BP will be lower because of the effect of gravity. Therefore, in the current scenario, the arterial line transducer is 20 cm above the level of the heart, which translates to approximately 15 mm Hg below the actual BP (choice B is correct).
Importantly, as long as the transducer is at the level of the heart, raising or lowering the arm that has the arterial line will not impact the BP (choices A and D are incorrect).1