Final answer:
Intubation is the procedure that may be difficult to perform on a patient with Down syndrome due to anatomical variations associated with the condition such as a larger tongue and smaller airways. The other options can typically be done without special difficulty.
Step-by-step explanation:
Which of the following may be difficult to perform on a patient with Down syndrome? Intubation can often be challenging in patients with Down syndrome due to anatomical variations common in the condition, such as a larger tongue, smaller mouth, and differences in the shapes of the airway. CPR, pulse oximetry, and splinting can usually be performed on patients with Down syndrome without special difficulty beyond considerations typical to the individual patient's needs and responses.