Though altitude sickness was also known to mountaineers, it was the balloonists who had traveled the highest and experienced the perils of the upper atmosphere. In fact, James Glaisher and Henry Coxwell had barely made it back alive after their balloon had soared to 36,000 feet on September 5, 1862. Missionaries trekking around in the Andes Mountains had reported mountain sickness as early as the 16th century, but even in the late 1800s, the harmful and fatal effects of high altitude were only known and not understood.
For about a century until Coxwell and Glaisher’s flight, scientists had known that the atmosphere is made up of a mixture of gases mainly oxygen, nitrogen, carbon dioxide, and water vapor and that these gases decreased as one climbed higher. However, they had not made the connection between the lower levels of atmospheric oxygen and its deleterious or even lethal effect on the human body. If we consider the treatment given to the unfortunate victim—cutting and opening the forehead—we realize that altitude science was not even born.
In the 1870s, some important discoveries about the effects of air pressure on the body were made by a French physiologist Paul Bert, known as the founder of modern aerospace medicine, who paved the path for space exploration as well as for the study of ocean depths. Bert proved that the symptoms of altitude sickness result from a deficiency of oxygen in the tissues of the body.
Bert also studied decompression sickness brought about by the rapid transition from high-pressure surroundings to that of low pressure. Underwater divers, pilots of unpressurized aircraft, and caisson workers are prone to decompression sickness because they work in surroundings with air pressure different from the air pressure on land. Bert demonstrated that high pressures of air causes huge quantities of atmospheric nitrogen to dissolve in the blood. During the rapid transition to low pressure, or decompression, this nitrogen forms gas bubbles that blocks capillaries.
Victims of decompression sickness may suffer from one or more symptoms such as lack of muscle coordination, sensory abnormalities, numbness, nausea, speech defects, personality changes, bent joints, and paralysis. The first explanation of the relationship between atmospheric pressure and blood oxygen levels appeared in Paul Bert’s scientific study in La Pression Barometrique in 1878.
Bert was inspired by the great Italian scientist Evangelista Torricelli, who had attracted considerable attention when he demonstrated his mercury barometer to the public. He explained that the fluctuations in the mercury column of a barometer corresponded to the changes in atmospheric pressure. Thus the science of meteorology was born. In honor of Torricelli, the torr came to be known as a unit of pressure equal to one millimeter of mercury. Toricelli who died at the age of 39, in 1647, was also the first to claim that we live at the bottom of the ocean of air, where atmospheric density is at its maximum; as we climb higher, the air becomes thinner resulting in low atmospheric density. Therefore, with increasing altitude, oxygen levels in our blood decrease with the decrease in oxygen.
Bert tested Toricelli’s hypothesis in his lab conducting experiments on sparrows, guinea pigs, and frogs in hypobaric chambers, (enclosures with inside air pressure lower than the atmospheric pressure). The results showed that a living being cannot survive without supplemental oxygen at high altitude. His research sparked a lot of curiosity about high altitude among his colleagues and balloonists, and some even volunteered to become subjects of his hypobaric chamber experiments.
Even though Henry Coxwell and James Glaisher had almost perished reaching about 36,000 feet on their flight, Gaston Tissandier, Joseph Crocé-Spinelli, a physicist, and Henri Thédore Sivel, a former naval captain and an experienced balloon pilot, wanted to break the record set by Glaisher and Coxwell. They would use the 106,000-cubic-foot balloon Zénith, and achieve their altitude goal with the aid of supplemental oxygen. Tissandier and Spinelli already had an impressive record flying the Zénith for 23 hours on 23-24 March 1875. They had traveled 356 miles (573 kilometers) from Paris to Arachon.
To gain some insights about the body’s acute reaction to the low pressure at high altitudes, the three French balloonists met with Paul Bert, a French physiologist, who conducted experiments in hypobaric chambers to show the relationship between atmospheric pressure and blood oxygen levels.
After placing them in his decompression chamber, Bert lowered the pressure until the pressure equaled the pressure existing at an altitude of 23,000 feet, which means a virtual height of 23,000 feet was reached. The pilots appeared to lose their sense of hearing and mental aptitude. Then he had them inhale oxygen supplied through a tube in the chamber. Their symptoms disappeared quickly.
Better informed about the lethal effects of thin air, Tissandier, Spinelli, and Sivel, each outfitted himself with an oxygen breathing apparatus—which had given positive results in Bert’s decompression chamber. The apparatus was made up of three bladders filled with a mixture of air and oxygen. The tube inside the bladder was connected to a mouthpiece which they had to hold by the hands to inhale the mixture. Their balloon, the 106,000-cubic-foot Zenith, took off from the gasworks at La Villete on 15th April 1875, at 11:32 a.m.
Meanwhile, Bert was concerned that the crew did not have enough oxygen for the flight and rushed a message to them. But his friends had already taken off and at 22,970 feet, they used the apparatus for the first time. Some reports mention that the aeronauts felt highly optimistic and the inhaled oxygen was the cause of the salutary effect. However, with the benefit of advances in altitude illness, it is well documented that at high altitudes individuals are known to become delirious and euphoric due to low levels of breathable oxygen. Humans who have not gradually acclimatized to new heights are even more prone to getting some symptoms of altitude illness at elevations as low as 10,000 feet, especially when they ascend rapidly.
The events that followed quickly after ascending to 22,970 feet are enough indication that they might have been affected by the low levels of oxygen in the air which corresponded to low oxygen levels in their tissues. Cold temperatures may also have aggravated their condition. Feeling euphoric, the aviators threw away huge quantities of ballast to climb higher. Quickly, the balloon shot up to 24,300 feet (7,400 meters). All of them became even more sick though they were supposedly taking oxygen.
One wonders whether they were able to draw enough oxygen from the bottles, or worse—had the oxygen delivery system failed miserably? They became short of breath, felt exhausted, and their pulses raced. Soon Tissandier passed out. When his consciousness returned, the Zenith was plummeting and Spinelli and Sivel were frantically throwing out ballast, and urged him along. Spinelli, perhaps confused and disoriented from the lack of oxygen to the brain, jettisoned an eighty-pound scientific equipment to make the balloon climb. They reached 26,250 feet (8000 m). Tissandier passed out again. Spinelli tried to shake him up but Tissandier drifted to sleep. According to a May 2, 1875 report in the New York Times, “At 7000 metres[sic] they lost consciousness of their acts, and were almost powerless… Sivel went on cutting down bags of sand. ’Yes,’ he cried gaily, ’and happy the one of us that returns!’ When the balloon had descended to 6,000 metres[sic], Tissandier came to himself to find his companions dead and the Zenith falling like a stone.”
When Tissandier’s faculties returned at 3:45 p.m., the balloon was plunging fast and his two companions lay slumped on the floor—their faces black and blue and streams of blood around their mouths and noses. In this dreadful situation, Tissandier managed to stay calm. He had a challenging task ahead to land the balloon, without any ballast. He managed to control the descent but the Zenith hit the ground hard. The flight had taken his hearing and the lives of his friends, even before the impact. He pulled the bodies of his comrades from the wreckage and staggered to a nearby farmhouse to find help.
Spinelli and Sivel, the martyrs to science, were buried in a cemetery in Pere Lachaise. Their beautiful tomb shows their draped life-size effigies resting peacefully.
The aeronauts were airborne for more than 4 1/2 hours and out of this a great deal of time was spent at extreme altitude above 18,000 feet and also above 25,000 feet, in a region that we now know as the Death Zone, where oxygen is one-third of that found at sea level. Even an experienced and acclimatized balloon pilot like Tissandier found himself drifting into a delirious state at 26,000 feet. He later wrote that the mind and body get so weak and the condition of stupefaction is so extraordinary that there is no consciousness of it.
“No suffering is then experienced; on the contrary, an inner joy is felt like an irradiation from the surrounding flood of light. One becomes indifferent. One thinks no more of the perilous position or of danger. One ascends and is happy to ascend. The vertigo of the upper region is not an idle word; but, so far as I can judge from my personal impression, vertigo appears at the last moment; it immediately precedes annihilation, sudden, unexpected, and irresistible.”
It appears that Glaisher and Coxwell escaped a fatal situation because they were seasoned and acclimatized balloonists, but they too had almost succumbed to the lethal effects of the thin upper atmosphere. Also, the Zenith encountered frost and colder and heavier air, which explains the frequent falling “like a stone,” and the need to control the descent by throwing out ballast, which subjected the Zenith balloonists to a wide range of altitudes and air pressures rapidly. The fact that Tissandier survived the flight underscores the necessity to acclimatize slowly to higher altitudes and also have better physical fitness; however, the Death Zone is lethal to anyone without supplemental oxygen.
The mishap revealed the need for a hands-free oxygen delivery system that could be relied upon in unconscious or disoriented conditions and led to the use of masks. Nevertheless, the tragedy angered people around the world and traumatized Bert. He never got involved in any manned high-altitude flights. The understanding of science and nature using balloons as a medium had to wait another 20 years.