Making the Invisible Visible
Uruguay is famous for football and Cowboys. So it was intriguing when I came across two postage stamps from the country, issued in 1998 celebrating its distinguished medical researchers. So I wondered if there was a connection. This blog is about José Luis Duomarco and Roberto Caldeyro-Barcia, two remarkable scientists from Uruguay, a story of making the invisible visible.
Medicine often advances when someone finds a way to measure something that was previously hidden. A pressure inside the body, a contraction of the uterus, the rhythm of a baby’s heart—these things happen continuously, but for centuries doctors could only observe their effects indirectly. Duomarco helped medicine understand the physical forces governing circulation, veins, the heart and abdominal pressure. A generation later, Caldeyro-Barcia applied rigorous physiological measurement to pregnancy and childbirth, transforming the way doctors understood uterine contractions and fetal heart activity.
José L. Duomarco: Understanding the Pressures Within Us
José Luis Duomarco trained at the School of Medicine of the University of the Republic in Montevideo, Uruguay and conducted much of his research alongside his clinical work. His scientific output was extensive and his interests ranged from cardiac function to venous pressure and even the physiology of humans in outer space.
One of Duomarco’s most important contributions was his systematic investigation of intra-abdominal pressure. Working with Ricardo Rímini, he studied the pressure within the abdominal cavity under normal and pathological conditions. Their findings were brought together in the 1947 book La presión intraabdominal en el hombre en condiciones normales y patológicas. The work was regarded as an important contribution to physiological knowledge because it did not simply describe observations; it examined them experimentally and connected them with existing theories.
Why does abdominal pressure matter?
Think of the abdomen as a closed compartment containing several organs. Changes in pressure within that compartment can influence the diaphragm, lungs, blood vessels and abdominal organs. Today, intra-abdominal pressure is an important clinical concept, particularly in critically ill patients. Duomarco’s work helped establish a physiological foundation for understanding these relationships. Today, intensives also use this pressure as a surrogate for pressures inside the adjacent pleural space, and to adjust ventilator settings.
But his curiosity did not stop at the abdomen.
Duomarco was fascinated by the circulatory system, especially the movement of blood through the veins. Together with collaborators, he investigated central and peripheral venous pressure, venous collapse, pressure gradients and venous return. His 1964 book on central and peripheral venous pressure became another major contribution to cardiovascular physiology.
One of the interesting aspects of Duomarco’s thinking was his willingness to challenge apparently obvious explanations. The veins are not rigid pipes; they are flexible tubes that can collapse. This simple physical fact has profound consequences for how blood returns to the heart. His curiosity even extended beyond Earth. In 1970, Duomarco published research on venous pressure in humans in space, showing how far his interest in physiology reached.
Roberto Caldeyro-Barcia: Listening to the Unborn Child
If Duomarco’s scientific world revolved around pressure and circulation, Roberto Caldeyro-Barcia’s great contribution was to bring measurement into the world of pregnancy and childbirth.
Caldeyro-Barcia is one of Uruguay’s most internationally recognized physicians. His research, conducted in collaboration with Hermógenes Álvarez an Obstetrician and others, transformed the scientific understanding of fetal life and labor. During the 1950s and 1960s, Caldeyro-Barcia and his colleagues developed methods for recording uterine contractions and fetal heart rate. These developments were particularly important because they allowed physicians to move from relying largely on clinical observation to obtaining objective physiological information about the fetus during pregnancy and labor.
Imagine childbirth before this revolution
Doctors and midwives could observe the mother’s contractions, listen to the fetal heartbeat with relatively simple methods and assess the progress of labor. But there was limited ability to continuously quantify what was happening inside the uterus or to interpret changes in the fetal heart rate in relation to contractions.
Caldeyro-Barcia helped change that. By recording uterine activity and fetal heart rate, researchers could study the relationship between what the uterus was doing and how the fetus was responding. This created the foundation for modern physiological monitoring during labor and became a cornerstone of modern perinatal medicine.
Caldeyro-Barcia helped physicians listen to the fetus scientifically
.The importance of this contribution went beyond Uruguay. His methods and observations were confirmed and adopted internationally, contributing to the development of modern perinatology—the branch of medicine concerned with the health of the fetus and newborn around the time of birth. Uruguay’s medical community has described this period as a major contribution to the emergence of perinatal medicine. In 1970, the Pan American Health Organization created the first Latin American Center of Perinatology (CLAP) in Montevideo, appointing Caldeyro-Barcia as its director. It provided training to doctors across the world, who became leaders in perinatology in their countries.
Two Scientists, One Scientific Philosophy
At first glance, Duomarco and Caldeyro-Barcia may appear to belong to different worlds. One studied abdominal and venous pressure, circulation and cardiac physiology. The other studied pregnancy, uterine contractions and fetal heart rate. But there is a remarkable connection. Both believed that physiology should be measured rather than merely guessed.
Duomarco converted invisible pressures and flows into measurable physiological phenomena. Caldeyro-Barcia converted the hidden activity of the uterus and the unborn baby’s cardiovascular response into signals that physicians could record and interpret. Their work also illustrates the importance of interdisciplinary thinking. Duomarco brought concepts from physics into medicine. Caldeyro-Barcia similarly combined physiology, instrumentation and clinical medicine to solve problems in obstetrics.
This was particularly remarkable because neither scientist worked in the scientific centers that traditionally dominated global biomedical research. Their work emerged from Montevideo, Uruguay, yet it traveled far beyond the country.
A Legacy That Still Matters
Modern medicine depends heavily on measurements. We measure blood pressure, oxygen saturation, cardiac rhythms, brain activity, blood flow and fetal heart rate. We use monitors because numbers and signals can reveal changes before they become obvious to our eyes.
Work of these two scientists reminds us that groundbreaking science does not always begin with sophisticated technology or enormous laboratories. Sometimes it begins with a simple question: What is really happening inside the human body? Duomarco asked what pressures were actually doing inside the human body. Caldeyro-Barcia asked what uterine contractions and fetal heart signals could tell us about the unborn child.
And perhaps that is the most fitting way to remember these two Uruguayans: one taught medicine to understand the pressures that move life; the other helped medicine hear the rhythms of life before birth. Their science began in Uruguay, but their questions—and their answers—became part of medicine’s universal language.
