Michael Croslin

Michael Croslin held more than 40 patents for medical inventions and established his own company, Medtek Corporation. His inventions include a computerized, digital blood pressure measurement device; a refractometer (used to measure the index of refraction of a substance) that measures levels of urinary sugar and protein; and a pump that measures and dispenses intravenous medications.

Born in 1933 in the U.S. Virgin Islands in Frederiksted, St. Croix, Michael Croslin was abandoned as a baby. A family named Britto gave him a home as a child and named him Miguel (later Anglicized as “Michael”). By the time he was 12, he fled the islands for the mainland United States. He worked odd jobs, living in Georgia for a time, and he obtained a brief education at a Jesuit school. He eventually wound up in Wisconsin, where he was adopted by the Croslin family. He, in turn, adopted their name.

Despite his uneven educational opportunities during childhood, Croslin was a brilliant student. By the time he was 14, he had graduated from high school. Within another three years, he had completed a bachelor of science degree at the University of Wisconsin.

Croslin joined the U.S. Air Force in 1950, serving in both Korea and Vietnam. Upon his return to the States and after discharge, he went back to school, earning a second bachelor of science degree, this one in mechanical engineering from New York University (NYU) in New York City. He has earned two additional degrees from NYU: a master of science degree in electrical engineering in 1963 and a Ph.D. in biomedical engineering in 1968. Simultaneously, he earned a master’s degree in business administration from Columbia University.

Croslin’s breakthrough invention was the Medtek 410 computerized blood pressure and pulse measuring device, invented in 1978. It successfully transformed blood pressure measurement from guesswork to accuracy. The old method of measuring blood pressure levels had several drawbacks, the greatest being the possibility—even probability—for human error. A technician pumped up a pressure cuff on the patient’s arm, placed a stethoscope over a blood vessel below the cuff, and then released the pressure manually, meanwhile watching a dial and listening for the heartbeat to be heard in the blood vessel.

The pressure measurements were recorded from the dial at the moment when the first beat was heard and again at the last beat. However, distractions, hearing ability, extraneous sounds, visual accuracy in reading the dial, speed of release, and other factors all made inaccuracies common. Croslin’s device measured the motion of the blood itself, produced results on a crystal readout, and could be calibrated digitally. In 1978, Croslin founded Medtek Corporation in Princeton, New Jersey, to produce and distribute his inventions, enabling him to profit from his own work.

Croslin and his digital blood pressure measurement invention have been showcased by the Franklin Institute Museum of Science and Invention in Philadelphia, Pennsylvania. According to an evaluation made in 1982, the Medtek blood pressure and pulse monitor model BPI 420, a later model of Croslin’s original invention, was approved for use on United States Air Force aircraft in case of emergency medical evacuation by air. This was a tribute to the reliability of the instrument, since it needed to be capable of operating accurately at a wide range of altitudes and under demanding circumstances.

It is a small portable unit capable of measuring both systolic and diastolic arterial pressures as well as pulse rate, using an oscillometric technique in conjunction with a microprocessor. The Medtek BPI 420 controls cuff deflation automatically at a set rate. The unit automatically adjusts to the surrounding barometric pressure calibrating for a range from 1,200 feet below sea level to an altitude of 30,000 feet. Surrounding noise also does not affect measurements. If an error occurs in the readout, either because of operator error or a malfunction of the unit, a message displays on the screen indicating the probable cause.