In the past I have spent a while in hospital and had the dubious pleasure of being an unusual case. On these occasions when able, I have been subjected to several groups of medical students who have been sent to find out what is wrong with me as part of their training.
On these occasions one thing that I have been asked frequently is "take a breath in and out" then please could you say "99", this enabled the more accurate students listening to my lungs to determine that on my right side the lung is not fully inflated.I had several pneumothoraces resulting in me having 4 chest drains inserted in my upper chest and having a one way valve on a pipe as a fashion item when I left hospital.I was lucky that the hole in my lung repaired itself and the pipe was removed.The phrase used to diagnose my chest problems has remained in my memory since.
I have researched this subject and found out that this phrase that is integrated in to a chest examination is used to elicit tactile fremitus and enable doctors to identify areas of consolidation or pneumothroax in the lungs, came about as a result of a mistake of language.The error has been repeated ever since from Doctor to medical student.
"Students are taught to say the number 99 in order to elicit these vibrations. In truth, this results from a misunderstanding of some postgraduate doctors in Germany being told to say the original German "neun und neunzig." This uses a dipthong not found in "ninety nine," but similar to "toy boat." Research has shown this dipthong is essential to the characteristic of the sound useful for diagnostics."
Dock W. Examination of the chest: advantages of conducting and reporting it in English. Bull NY Acad Med 1973;49: 575-582
So it seems the phrase now used is not as originally intended