Use of Past Perfect

Hello everyone

Here's a short paragraph taken from an http://www.horizonresearch.org/obeexplanations.html:

"In 2002, a group of Swiss doctors carried out a procedure that is often performed on patients with intractable epilepsy. Electrodes were implanted in the brain and used to stimulate different portions of the brain. The aim was to find an abnormal brain circuit that may have been causing the recurrent seizures. In this case, as the doctors had been doing this, quite unexpectedly the patient had reported seeing herself 'lying in bed, from above' and also 'floating' near the ceiling. However, she had not had a full out of body experience, as she had only been able to see her legs and lower trunk".

I just can't understand why the Past Perfect is being used in these cases.

Thanks in advance.