Early physicians recognized that illness often was associated with fever, but it took centuries for scientists to develop the means to measure body temperature. Although Galileo in 1592 was the first to fashion a crude thermometer, it was another Italian scientist, Santorio Santorio, who was the first to take oral temperatures in 1625. His thermoscope, as it was called, was large and cumbersome, and took hours to perform a single measurement.
It was not until the mid-1800s that the German physician Carl Wunderlich developed a foot-long thermometer that could take clinical temperatures. In 1868, he published his data of more than 1 million axillary readings from more than 25,000 patients. He determined that there was a diurnal variation in daily body temperatures ranging from 97.3°F in the morning to 99.5°F in the evening. He also originated the standard of 98.6°F as “normal body temperature” that we use today. His readings took 20 minutes to perform, and for anyone but the most patient of physicians, this was not a practical device.
When I opened my first practice in 1986, I was intrigued by an advertisement in Contemporary Pediatrics that caught my attention, and days later I was the proud owner of a FirstTemp tympanic thermometer. The manufacturer (Intelligent Medical Systems; Carlsbad, California) promised the device’s measurements were as accurate as oral and rectal temperatures taken with glass thermometers. I was initially skeptical of this high-tech thermometer, but within weeks it proved to be a very popular device among staff, providers, and patients. The reason it was successful was that it required little patient cooperation and took temperatures in seconds, and it produced measurements comparable to those obtained with our digital oral and rectal thermometers.
Before the Haemophilus influenzae type b vaccine first became available in 1985 and the first pediatric conjugate pneumococcal vaccine became available in 2000, pediatricians routinely encountered severe illnesses in patients that included meningitis, septic arthritis, osteomyelitis, and sepsis. These were so common that blood cultures and spinal taps were routine office procedures. Before the introduction of the H influenzae and pneumococcal vaccines, 3% of young febrile children without a focus of infection had positive blood cultures for H influenzae, Streptococcus pneumoniae, or Neisseria meningitides. Six percent of those patients positive for pneumococcus also were discovered to have meningitis, while up to 20% of positive blood cultures for H influenzae were associated with meningitis. Today, the incidence of occult bacteremia is 0.5%, and we rarely perform blood cultures or spinal taps in the workup of infections, except in febrile young infants. The key point is that, just 2 decades ago, parents and pediatricians were alerted to the possibility of severe pediatric illness by the presence of fever, and they were comforted by its absence. Today, documentation of a fever alerts physicians regarding the cause of the associated symptoms. In most situations, there is an infectious cause with rheumatologic illnesses, malignancy-related fevers, and period fevers being much less common.
Ron Benincasa and Gary O’Hara invented the first infrared ear thermometer, the FirstTemp mentioned above, which was introduced to medical practices in 1984. Because of its speed, it became extremely popular and eventually sold about 80,000 units. It was replaced by a more streamlined unit called the Genius and the company was eventually sold to Sherwood Medical (Now Covidien) in 1993. You can still purchase the Genius 3 online for $379 dollars.
Ron and Gary reinvented infrared thermometry about a decade ago, forming a company called Thermomedics, producing first accurate non-contact clinical forehead thermometer called the Caregiver PRO-TF300-CS. Ron estimates the company has sold more than 80,000 units and studies have demonstrated that the thermometer is extremely accurate. It takes temperatures in 2 seconds and two AA batteries can provide up to 15000 measurements. In my own experience it produces temperature measurements comparable to that produced Exergen’s TAT-5000 contact thermometer, while costing substantially less.