A TENS unit is a battery, waveform generator, current-control circuit, and a few electrodes. It sends pulsed current through the skin to recruit nearby nerve fibers. The goal is not to repair a strained muscle, realign a joint, or remove inflammation. It is to change the neural traffic associated w/ pain. A rough model is: […]
A pulse oximeter does not directly count oxygen molecules, measure the partial pressure of oxygen, or sample arterial blood. It sends red and infrared light through tissue, extracts the part of the optical signal that changes with each pulse, and maps that signal through an empirical calibration curve. A rough model is: $$ \text{red/IR transmission} […]
Triage is not just “who looks sickest” but rather a real-time decision system w/ asymmetric risk The ED has to make a first routing decision before it has the full chart, labs, imaging, response to treatment, or a true differential diagnosis. At its core triage is risk estimation under incomplete information. A reasonable technical def […]