Colorado and Altitude Research – More History
The 1911 Anglo American expedition to Pikes Peak established the principles of ventilatory control at altitude, most of which hold true to this day. Led by John Haldane, this landmark study combined investigators from Oxford, Yale, and Colorado College. They showed that ventilation increased steadily during the first several days at altitude. This gradual increase was punctuated by periods of dysregulation, especially during sleep, that could be normalized with supplemental oxygen. During exercise, ventilation increased dramatically compared to sea level, despite no change in oxygen requirements. They also showed that altitude sickness was due to decreased oxygen, not carbon dioxide as previously thought. This observation was primarily the result of Mabel FitzGerald's forgotten contribution to the expedition. As a woman in Victorian society, she was not accepted in science and was forced to travel alone from mine to mine, studying the ventilatory responses of miners adapted to high altitude. These observations shifted the focus of long term breathing regulation at altitude from carbon dioxide to oxygen.

The high altitude grasslands of South Park, Colorado provided another site for early investigations into altitude illness. Ranchers noticed that cattle bought at low altitude died at an alarming rate while those bred from surviving cattle fared much better. In 1913, an endowment was set up at the Experiment Station of the Colorado Agricultural College (now Colorado State University) to investigate this problem. A veterinarian named George Glover and pathologist Isaac Newsom answered the challenge. They found that the disease struck cattle living above 8,000 feet and was most prevalent during the winter months. Affected cattle showed severely swollen necks and eventually died of heart failure. All symptoms disappeared when affected cattle were brought to lower altitude. Such research laid the foundation for future studies exploring the effects of high altitude on humans.

Traveling to the summit of Pikes Peak in 1929, the husband and wife team of Arthur and Anna Louise Costello Grollman investigated changes in cardiac function at high altitude. The Grollmans used their homemade equipment to make daily measurements of cardiac output (the amount of blood pumped by the heart) using each other as subjects. When these values were compared to sea level measurements, a surprising trend arose. During the first day at 14,115 feet, cardiac output remained at sea level values. Over the course of the next four to five days cardiac output slowly increased, before decreasing back to sea level values within two weeks. The Grollmans later showed immediate increases in cardiac output at altitudes above 15,000 feet. This led them to conclude that something besides oxygen, likely the central nervous system, was responsible for the changes in cardiac output seen on Pikes Peak. Scientists have yet to answer this puzzling question, but it is clear that the human heart can tolerate altitudes as high as the summit of Mount Everest.

The Harvard Fatigue Laboratory led by David Bruce Dill was the only place investigating the effect of altitude on athletic performance in the early twentieth century. The lab's earliest findings showed that endurance performance decreased when breathing hypoxic gas at sea level but the authors wondered how acclimatization to high altitude would impact performance. For the next forty years, they traveled the globe in an effort to fully answer this question. The first expedition went to the Leadville Fish Hatchery in 1929. Endurance performance gradually improved as subjects adapted to altitude, but aerobic capacity remained about 20% below sea level values. Subsequent expeditions showed that aerobic performance and the ability to process oxygen (VO2 max) both decreased as altitude increased and these values did not return to sea level baselines even after acclimatization. These initial studies ignited a line of research that continues to this day.

Improvements in sanitation and acceptance of the germ theory of disease combined to decrease infant mortality throughout the twentieth century. Despite this, Colorado's infant mortality rate remained well above the national average. With the end of World War II and seeing the impending baby boom, the University of Colorado Medical School was determined to reverse this trend. The systematic study of birth weights by county was led by John Lichty. It showed that mothers in high altitude counties gave birth to smaller babies at an alarming rate. Investigators initially examined differences in nutrition, ethnicity, and medical care but these factors could not explain the low birth weights. In addition to weighing less, the high altitude babies were shorter and had smaller heads. This suggested slower growth in utero. The project reluctantly attributed slower growth rates to the reduced oxygen levels of altitude. Later investigations showed that lower birth weights were associated with increased mortality even if the pregnancy went to term.

The high mountains surrounding Aspen provided the unlikely site for the first English language account of high altitude pulmonary edema. It was New Year's Eve 1958 when Dr. Charles Houston received a panicked phone call from a backcountry skier saying his friend was stranded miles from town and on the verge of death. With the impending storm and the night's festivities, organizing a rescue party proved extremely difficult, but Dr. Houston and others managed to get the incapacitated skier to the local hospital. The patient's symptoms were hesitantly attributed to pneumonia but doubts lingered. There were no signs of infection or fever and the symptoms had disappeared under treatment in an oxygen tent. These factors pointed to temporary heart failure induced by cold, exertion, and altitude. Interestingly, it was the patient's mother who most strongly questioned the diagnosis, insisting that the problems were related to altitude. Publication of this case report in the New England Journal of Medicine generated immediate interest in this puzzling condition and led to the discovery of previous Spanish language and ancient Buddhist accounts of pulmonary edema. Within the next few years, studies showed the victim's mom was right all along. Elevated blood pressure in the pulmonary artery, and not heart failure, was responsible for fluid accumulation in the lungs.