It took decades of deliberation between the American Academy of Ophthalmology and the Joint Commission before it was settled that eye color was a not a vital sign. The major piece of evidence supporting this decision is that when a patient is coding with a heart rate of 0, respiratory rate of 0, a blood pressure of 0/0, the patient's eye color remains the same.
On a day-to-day basis, it is of general consensus that patient height rarely fluctuates. Because there is no parallel to hypotension or hypertension, height as a vital sign has been abandoned for the time being. Some argue that height can certainly fluctuate, particularly if the patient is performing squats.
This is a rare issue where cardiologists and nephrologists are on the same side, as they consider daily weights a vital sign in patients with marked volume overload due to congestive heart failure or end-stage renal disease (ESRD). Do not be surprised if daily weight replaces pain as the fifth vital sign. For the time being, sadly, it is a nonvital sign.
Since we use I's & O's for input and output, why not I's & O's for innies and outies? Under new Secretary of Health and Human Services Tom Price, expect several hundreds of millions of dollars to be shunted towards research into this field. Who knows, this nonvital sign may become a new vital sign in the near future.
It is of expert opinion that using shoe size as a vital sign falls into the same problem as using height as a vital sign. Though there are exceptions, shoe size generally doesn't fluctuate on a daily basis and a stable foot size can mislead a health care professional into thinking a patient isn't coding. The real problem is this: if shoe size becomes a vital sign, then why not bra size or pants size? This is one of the most controversial issues in modern medicine, more so than the future of the Affordable Care Act (ACA).