A number of other Brooklyn men were sent by Smith to the Brooklyn City Hospital, where, interestingly, the cases became the special fascination of a young intern there, Dr. Walter Reed, later to be one of the best-known physicians in the world as a result of his research on yellow fever. Like Smith, Reed also kept extensive notes on each caisson victim to come under his care and these he subsequently turned over to Smith. As Roebling would write, it was hoped that Smith’s efforts and conclusions would be made public eventually “for the benefit of future works.”
Smith never used the term “bends.” He called it the caisson disease, a name he was the first to employ and that is still used as the formal designation. He did a commendable amount of original research into the history of the subject and was thoroughly familiar with what Jaminet had written in a lengthy report published in St. Louis the previous year. * Smith described Jaminet’s observations as “exceedingly valuable,” but found it “especially to be regretted” that Jaminet’s basic remedial routine had been merely to keep the patient lying on his back with his feet elevated slightly and to administer whiskey or beef broth.
From what he read and from his own observations Smith put together a number of theories, several of which were the same as conclusions reached in France some twenty-five years earlier. The disease, he decided, depended upon increased atmospheric pressure, but always developed after the pressure was removed. Attacks never occurred while the men were still under pressure, only afterward—as had become obvious to almost everyone. So there was a very good chance, he decided, that the principal cause of the trouble was “locking out” too rapidly. “Indeed,” he wrote, “it is altogether probable that if sufficient time were allowed for passing through the lock, the disease would never occur.” This, he knew, jibed with what the French mining engineer M. B. Pol had concluded in 1845 and later expanded on in a most interesting memoir published in 1854. “Experience teaches,” Pol wrote, “that the ill effects are in proportion to the rapidity with which the transition is made from the compressed air to the normal atmosphere.” In St. Louis Jaminet too had hit upon the same idea after being taken by a terrible seizure himself, but Jaminet thought it even more important to increase the pressure slowly when the men were going in. Smith it seems never suffered any discomfort from his time in the caisson.
To make things easier for the men after they emerged from the lock, Smith recommended that no climb up a long flight of stairs be necessary at that point. To have put the locks at the bottom of the shaft as Eads had was a serious mistake, he said. The arrangement in Brooklyn had been better. That way the climb was made “in the compressed air, instead of immediately after leaving the lock, when the system is more or less prostrated.” The elevator Roebling installed had been a wise measure, but it had not wholly alleviated the problem.
But Smith did not see how, in all practicality, the locking-out procedure could be changed much. What might be sufficient time in the lock for one man, he reasoned, would be too short for another, and far less work would be accomplished if the time in the lock were prolonged greatly. Delays would be very expensive for the Bridge Company. Besides, the men themselves would want no part of it. About all that could be done, he concluded, was to make the time required in the lock proportionate to the pressure. But even that time could only be “as great as is consistent with the circumstances.” For the New York caisson Smith established a regulation that at least five minutes more in the lock would be allowed for each additional “atmosphere,” or for every additional 14.7 pounds of pressure, which meant that for every three pounds of pressure added inside the caisson, Smith wanted the men to take a minute longer coming out. So at a depth of, say, sixty-five feet, with the pressure at thirty pounds, the men should spend five minutes in the lock on their way out; at seventy-five feet, with the pressure at thirty-three pounds, they would spend perhaps six minutes. Smith was not asking for very much, in other words. Even so, the regulation was followed only infrequently. “The natural impatience of the men to reach their homes,” he wrote in a tone of despair, “makes the delay in the lock irksome, and great firmness is required on the part of the lock tender to prevent the escape cocks being opened more widely than is consistent with safety.” One of the first steps in such work, he said, ought to be the employment of reliable lock tenders.
But despite his recognition of rapid decompression as the chief cause of the mysterious sickness, Smith remained convinced that susceptibility was still largely a matter of “special predisposition,” as he called it. Some people, he said, were simply more susceptible than others. It was commonly known, he said, that certain people had a predisposition to pains in the joints just prior to a thunderstorm. These pains, as he said, were generally considered to be of rheumatic character and caused by dampness, but Smith now thought differently. The pains suffered by his caisson workers were precisely the same, he said, only, of course, immensely intensified. So very likely anyone who could feel weather in his bones was actually feeling shifts in atmospheric pressure, and just as some people could feel such things and others could not, so some people would fall victim to the caisson disease while others would not.
Fat people and heavy drinkers, he was convinced, were more susceptible than anyone else. Men new to the work also stood a greater chance of being hit by an attack than those who had been going into the caisson for a length of time and so had had the pressure build up on them slowly. New hands suffered worst during the first week he noted. The ideal caisson worker in his view was a spare man of medium height in his twenties or thirties, a description that would have applied to Washington Roebling, among others.
But of more importance was Smith’s contention that the amount of pressure a man was exposed to and length of time spent in the caisson were as much a part of the problem as rapid decompression. So in this he agreed completely with Eads, Jaminet, and Roebling. “The testimony of all observers,” he wrote, “is that the liability to attack is directly as the duration of the stay in the caisson.” The common explanation given for Roebling’s collapse in the Brooklyn caisson the night of the fire was not that he had been coming up too fast, but that he had been staying down too long. Smith concurred with the explanation. In fact, the explanation followed perfectly out of the conclusion he had come to concerning the real root of the problem.
14
The Heroic Mode
As it is now demonstrated that the method of compressed air is applicable to a great range of engineering operations, and offers many peculiar advantages, it is extremely desirable that the principal objection to its employment, viz., the discomfort and danger to the workmen, should be reduced to a minimum. To this end I offer the following suggestions…
—ANDREW H. SMITH, M.D.,
The Effects of High Atmospheric Pressure, Including the Caisson Disease
SMITH said the caisson disease could be explained on mechanical principles. He said it was caused by the effect of abnormally high atmospheric pressure on the circulatory system. Under pressure, the blood was not distributed according to the normal physiological demands of the body, “but in obedience to overpowering physical force.” As he saw it the envelope of heavy air in the caisson pressed against the surface of the body forcing the blood into the center of the body. The blood “retreats,” he wrote, “from the surface to the center, and accumulates there until an equilibrium of pressure is produced.”
Smith held, however, that a man’s circulation could adjust somewhat to such unnatural conditions if the conditions were experienced by degrees. And the longer a man stayed down in the heavy air, and the heavier the air, the more the circulatory system would be affected. But when the pressure was removed suddenly—if a man were to waste no time getting through the air lock—then the blood vessels would fail to assume their natural condition in an instant, proper circulation would not be restored quickly enough, and “disturbance of function will result.”
Smith was quite right that rapid decompression was the secret to the myster
y, but his explanation of why was wrong. His call for slower decompression was a commendable step in the right direction certainly, and seemed radically cautious at the time. (In St. Louis, for example, Dr. Jaminet wanted his men to spend an extra minute in the lock for every six new pounds of pressure, indicating that perhaps Smith’s convictions on the matter were twice as strong.) But even so, as a preventive measure, Smith’s new locking-out procedure, even when it was followed, was so inadequate as to be of little real consequence.
The mystifying disease was, in fact, caused by the effect of too rapid decompression on circulation, but for reasons other than Smith had arrived at. The leg pains, the paralysis, the swollen joints, the agonizing stomach cramps, were caused by the liberation of nitrogen bubbles from solution in the blood stream and in the tissues of the body upon the sharp reduction of atmospheric pressure.
Under pressure the normal nitrogen gas in the blood dissolves to a high degree, then returns to a gaseous state—in the form of bubbles—when and if the pressure is suddenly relieved. Set free in the body fluids such bubbles can cause great damage. If liberated in the spinal cord, for example, they can cause total paralysis. But if pressure is relieved gradually, the gas comes out of solution slowly and is removed by the lungs.
The savage pains of the bends are caused by a stoppage of the oxygen supply in the blood stream. The nitrogen bubbles released by too rapid decompression create blocks in the blood stream—the same as mechanical blocks—that keep the oxygen in the red blood cells from reaching the tissue. The red cells fail to get past the nitrogen bubble, the tissue is denied the oxygen it must have, and the result is dreadful pain. This denial of oxygen-bearing blood—called ischemia—is much the same as what happens in a heart attack. So an attack of the bends might be likened to a heart attack in different parts of the body, most often the limbs and joints.
The level of pressure in the caisson and the time spent by an individual in the caisson do have a direct bearing on the problem and so Smith was right to keep the work shifts as short as possible, a policy that is still adhered to in caisson and tunnel work when pressures are extreme. Smith’s nine rules were also sound policy, in that they contributed to the over-all fitness and health of the men and fit, healthy men are less likely to be victims of the bends than those who are not. Fat men are also more prone to attacks, as Smith surmised, since the nitrogen bubbles tend to collect and dissolve in fat tissue. And from all that is now known about the bends—from subsequent experience in construction work, from underwater research and the space program—it appears that some people are indeed more susceptible to the disease than others, just as Smith declared.
Smith was, in fact, a keen and intelligent observer and deserves great credit for his work. His thesis of slower decompression was the key to the puzzle. The only problem was he did not carry it anywhere near far enough.
A man’s health did depend mainly on how sudden and great a change he was subjected to on coming out of the caisson back to normal pressure. If there was to be damage done it happened then. Time in the caisson, the amount of pressure the men were working under, their individual physical make-up and condition, even the temperature both in and outside the caisson, were all important contributing factors. But it was the speed of the exit that really mattered. And by modern standards the men in the New York caisson were making their exits disastrously fast—even when doing as Smith wanted and taking a few extra minutes in the lock. Today the accepted safe rate of decompression is no less than twenty minutes for each atmosphere, or more than a minute for every pound of pressure. So by that standard, at a depth of sixty-five feet in April of 1872, every man coming up from the New York caisson should have spent at least twenty minutes in the lock, instead of two or three as was the average, or five or six as Smith urged.
That bubbles of nitrogen were the true cause of the dreaded disorder had already been discovered in France by a professor named Paul Bert, and at about the same time Smith was conducting his research. But the discovery would not be published until August of that year, and although Smith would read what Bert had concluded before formally presenting his own conclusions, he would decide that Bert was mistaken.
Smith was quite right about one other very crucial matter: how to relieve the agony of the disease. Just when the answer dawned on him is not clear, but it appears quite noticeably twice in his case notes.
The first time was in February, in the case of the foreman Joseph Brown, already quoted. “Pain continued until he went down again for the afternoon watch, when it ceased immediately.” Then in April, Smith described the case of another foreman named Card, who was hit by an attack of extreme trembling, followed by paralysis in the legs and bladder. Smith writes that the man remained in this state for two full days, but then adds, “After the paralysis had passed off in a measure, he went down again into the caisson and remained for a short time with decided benefit.”
The quickest, surest way to relieve the pain was to send the patient right back into compression and when it came time for Smith to present his final report the next year he would write this:
It frequently happened under my observation that pains not sufficiently severe to deter men from returning to work were promptly dissipated on entering the caisson, to return again on coming into the open air. Indeed, I do not remember a single exception to the rule, that any pain which may have been felt before, disappeared almost immediately on going down.
Smith was aware, too, that Pol had prescribed returning the patient at once to the compressed air and that Dr. Antoine Foley, also of France, had said the same thing in a paper published in 1863. Later that same spring of 1872, in his own annual report, Roebling would write that most men got over their troubles either by suffering for a time or “by applying the heroic mode of returning into the caisson at once as soon as pains manifested themselves.”
But the puzzling thing is that Smith never seems to have actually prescribed this “heroic mode.” Not once, according to the records, was a man suffering from a violent attack of the bends taken back down into the caisson. It was only the man who felt fit enough to go down on his own, to work, who ever benefited from this simplest and most effective of all remedies. Smith’s explanation was that the means of access to the caisson were such that to take any but a comparatively healthy patient down inside would have been too difficult—“even if he could be comfortably cared for while there, or if his presence would not interfere with the work.” The remedy was just too much bother, he seems to be saying. It would have deterred progress the same as would more time taken in locking out.
But equally important, it seems, was the fixed idea most of the men had that the pressure itself was the cause of the trouble. They could not get rid of that idea. The thought of going back for more pressure when they were in their agony—of getting back on the horse, so to speak—was more than any of them were up to and particularly if neither the doctor nor the engineers in charge ever insisted on it. The less risky course seemed simply to hold on and suffer it out.
At a depth of sixty-eight feet the caisson’s steady plunge into the earth slowed abruptly. The men were into quicksand now and the going became extremely tedious. The big clamshell dredge buckets dropping down the water shafts were almost useless against the fine sand that, in combination with small stones and boulders, had compacted into a substance about as hard as rock. The teeth of the buckets made hardly any headway at all. The point of a crowbar could be hammered into the material, but just barely. And though the sand pipes still “answered admirably,” as Roebling put it, even they were constantly clogging with coarse gravel and stones. The speed of descent was now perhaps a foot a week.
At a depth of seventy feet Roebling ordered that daily soundings be taken for bedrock. So a couple of men with sledge hammers and a ten-foot iron rod began probing the work surface and among the others there was talk of the caisson going twenty or thirty feet more before Roebling would call a halt. Then at a depth of seventy-one feet the firs
t death occurred.
On the morning of April 22, a heavy-set German, a common laborer, went down through one of the air locks and into the caisson for the first time. Two days before, when he applied for work, the man had given the name of John Myers. Dr. Smith had judged him to be about forty and in good health. The pressure by this time was thirty-four pounds, and the workday, shortened once again, was five hours.
According to Smith’s subsequent account of the case, Myers worked the morning shift, just two and a half hours, without any discomfort, and hung about the yard for nearly an hour after coming up, apparently heeding the doctor’s rules about rest. But then he had complained of not feeling well and started for his boardinghouse, which was quite close by. “As he passed through the lower story of the house,” Smith wrote, “on his way to his room, which was on the second floor, he complained of pain in the abdomen. While ascending the stairs, and when nearly at the top, he sank down insensible, and was dead before he could be laid upon his bed.” An autopsy at the city morgue showed that brain, heart, and kidneys were perfectly normal. The lungs, however, as Smith reported, were “congested to a very remarkable degree.”
On April 30, just eight days later, with the pressure still at thirty-four pounds, Patrick McKay, of Ireland, age fifty, was listed as the second fatality attributable to the caisson disease. McKay had been working in the caisson for four months with no ill effect. On the afternoon of the 30th he had stayed down a half hour longer than usual, and on his way out through the lock, the others in the lock saw him suddenly slump to the floor, his back against the iron wall, quite insensible. He was at once carried into the open air and taken to Park Hospital, where Smith looked in on him some time later that evening. “He was there in an unconscious condition,” Smith wrote in his notebook; “face pale and dusky; lips blue; pulse irregular and feeble. Under the administration of stimulants, he recovered some degree of consciousness, and begged incessantly for water.” But only a little later the man went into convulsions and died. This time, however, the autopsy indicated Bright’s disease in the kidneys and Smith would conclude that “the effect of the compressed air was merely to hasten an event which, at best, could not have been very long delayed.”
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