If a nurse (or paramedic :-) ) is suctioning a patient' airway using in-line suctioning, the best method would be to hyperoxygenate the patient before disconnecting the ventilator.
It's necessary to hyperoxygenate a patient before suctioning because they will be decreasing their oxygen in-take the longer the suctioning takes place. This allows the nurse/medic to have a little extra time to finish suctioning and only have to do it once.