Which site is a preductal site for pulse oximetry in an infant with suspected pulmonary hypertension?

Which site is a preductal site for pulse oximetry in an infant with suspected pulmonary hypertension?

• A. Right wrist
• B. Left ankle
• C. Left wrist
• D. Forehead

Answer: (A)

Measuring oxygen saturation at a preductal site is important when evaluating suspected pulmonary hypertension because it shows the blood that has not yet mixed after passing through the ductus arteriosus. The right hand is used as the preductal site because the arteries supplying the right arm branch off the aorta before the ductus arteriosus connects to the descending aorta, so the blood here reflects oxygenation prior to ductal mixing. Postductal sites, like the feet, reflect blood after it has potentially mixed with less oxygenated blood after passing the ductus arteriosus, which can reveal a drop in saturation if there is ductal shunting. The forehead is not used for standard pre/post-ductal pulse oximetry in this context, though cerebral oximetry exists separately. So, the right wrist is the best choice for assessing preductal oxygen saturation in this scenario.

Measuring oxygen saturation at a preductal site is important when evaluating suspected pulmonary hypertension because it shows the blood that has not yet mixed after passing through the ductus arteriosus. The right hand is used as the preductal site because the arteries supplying the right arm branch off the aorta before the ductus arteriosus connects to the descending aorta, so the blood here reflects oxygenation prior to ductal mixing.

Postductal sites, like the feet, reflect blood after it has potentially mixed with less oxygenated blood after passing the ductus arteriosus, which can reveal a drop in saturation if there is ductal shunting. The forehead is not used for standard pre/post-ductal pulse oximetry in this context, though cerebral oximetry exists separately.

So, the right wrist is the best choice for assessing preductal oxygen saturation in this scenario.