Forces applied by nasal speculums during transsphenoidal operations.

The forces exerted by nasal speculums were measured during the transsphenoidal approach to the pituitary. The highest forces were found to occur at the beginning of surgery when the speculum had been spread to the desired opening (reaching 42 kg). This force decreases during surgery due to the time dependent motion of the biological structure distant from the applied pressure (relaxation). The amount of relaxation that occurred was measured but was found not to be high enough to indicate damage to the tissues adjacent to the speculum. It is also concluded that this type of instrument was underdesigned for its intended function.