Blood pressure devices
Before the invention of the sphygmomanometer (blood pressure monitor), there was no way to measure blood pressure without making an incision.
The first blood pressure reading
Reverend Stephen Hales was the first person to measure blood pressure. In the early 1700s he made a small cut on a restrained horse and inserted a brass pipe (cannula) attached to a 9 foot tall glass tube (manometer) standing upright. Hales untied the ligature of the artery and slowly blood rose in the glass tube, slightly rising and falling at each pulse. This was a major moment for Hales to develop the fundamentals of comparative physiology, despite being inaccurate and an experiment of nightmares.
The first non-invasive sphygmomanometer
It wasn't for another 100 years, 1828, until Jean Leonard Marie Poiseuille would invent the first non-invasive sphygmomanometer. Poiseuille's device used a metal band to compress the arm and a mercury column to measure the pressure.
Portable monitors
50 years later in 1881, physician Samuel von Basch invented a simpler and more portable monitor. This one could be carried in a bag by physicians. It used a spring instead of mercury to measure more accurate readings.
Cuff-based monitors
15 years later in 1896, physician Scipione Riva-Rocci invented a groundbreaking monitor which used a cuff and a stethoscope. It's the blood pressure monitor you think of with the pump and gauge.
Electric blood pressure monitors
Finally, 70 years later in the 1970s, electronic blood pressure monitors were invented. Mercury wasn't needed for these readings.
One-handed blood pressure monitors
Most recently, one-handed blood pressure monitors are becoming popular. They may not be quite as accurate, but they're ideal for people with mobility constraints or for people who live alone.
Why so many iterations?
Blood pressure is a dynamic measurement. A monitor needs to be accurate and since blood pressure can vary significantly from moment to moment, they have to be fast and precise. On top of that, they need to be easy to use by physicians or patients at different ages and with different abilities.
A tale of two paradigms
It's a classic design story arc. What began as a complex and invasive device has evolved to fit demands and preferences of people. When we are faced with a complex problem, it's easy to get bogged down in the details. If we can step back and look at the problem from a high level, we may be able to find a simple solution that is both effective and efficient.