Patient portal using wordpress

Yes its possible to link a file to buddypress member as admin.

An important piece of the API is the BP_Attachment class. You can extend it to be ready to receive user submitted files, validate these submissions and finally write the files in a /wp-content/uploads’s subdirectory you define.

You can review more details and final solution at https://codex.buddypress.org/plugindev/bp_attachment/