Science and Industry
on the World Today
THE collision of two airliners over the Grand Canyon last summer was shocking because of the number of lives lost, but collisions in the air are not unusual. Between 1948 and 1955, according to the Civil Aeronautics Board, 226 persons lost their lives in 127 collisions, 15 of them involving commercial aircraft. The 1955 rate climbed 31 per cent over the year before. Air Force safety officers report their planes have averaged about seven midair collisions a month since 1952.
Even more ominous for the future is the number of near misses. An Air Transport Association survey is reported to have shown an average of four near misses a day in a typical month.
The growing collision risk is of course one aspect of the much larger problem of air congestion. But while the ultimate solution of overcrowded airways probably depends on better traffic control systems and more accurate navigational devices, the answer to collision risk seems simpler. Obviously the old principle of “see and be seen” no longer works. Many aircraft have blind spots. Clouds hide other planes. Traffic density is constantly increasing — and the complex instruments a pilot has to watch on a big plane make it hard for him to keep a sharp lookout, He needs a warning device to tell him at once when other aircraft come dangerously near.
Now the Air Transport Association, which has been on the lookout for such a device, has endorsed a Proximity Indicator system proposed by Collins Radio Company. Collins calls it a “radar cocoon.” The indicator consists of a protecting net of radar waves thrown out around a plane in all directions, combined with an automatic danger signal.
Six radar antennae provide the net — four aimed at the horizon and two covering a hemisphere each above and below the aircraft. When another plane comes within two miles on the same level or within 800 feet above or below, a radar signal from an antenna picks it up. At once red lights start flashing on a board in front of the pilot. The position and shape of the light tell at a glance whether the other plane is above or below and in what direction. A shift in the light pattern shows instantly if the intruder comes close or changes bearing. This flashing light system makes it unnecessary for an observer to keep his eyes glued to a tiny radarscope. The range of the device is believed ample to provide more than the eleven seconds that the ATA estimates the pilot needs to change his course to avoid a collision.
Collins estimates that it will take about a year to develop a working model of the device, and production models are not expected before September, 1958. The company reports that it already has under negotiation orders for more than 800 units, which will cost $6000 to $7000 apiece.
Collins plans eventually to make the Proximity Indicator still more useful by tying the radar receiver to a compact computer. This will take the direction and speed of a nearby plane — obtained through Doppler radar — and not only compute almost instantly whether a collision threatens, but also indicate to the pilot which way he must turn to avoid it. But these additional features, which will add $3000 to $5000 to the cost, will require a great deal of development and aro not expected to be ready until November, 1959.
While the cost of the equipment will put it beyond the reach of many private plane owners, the Proximity Indicator will provide them with one benefit at small cost. Any plane that carries an inexpensive microwave receiver will pick up an audible radar signal when a plane equipped with a Collins Indicator is nearby. Some Strategic Air Command craft, incidentally, are using a somewhat similar system right now. Certain kinds of static in their electronic equipment warn them that another plane is intruding on their air space.
The spectacular triumphs of medicine in recent years have been largely the work of the chemist’s wonder drugs. Yet engineering techniques, both mechanical and electronic, have produced tools and devices of tremendous value to both research and clinical medicine—iron lungs, electron microscopes, shock therapy machines, radioisotopes, to name only a few. Most dramatic of all, perhaps, are the artificial internal organs in which man attempts to use motors and pumps, plastic pipes and electrical currents, to duplicate vital functions of the human body.
Artificial kidneys have been built with plastic membranes that carry out the natural processes by which waste matter is taken from the blood. These are already easing pain and saving lives by giving the body time lo rebuild the natural functions. Even more interesting are the machines that do the work of the heart itself— machines that are leading to daring new types of surgery and, according to some enthusiasts, may someday make possible actual replacement of the heart.
A number of these heart-lung machines are now in various stages of development in medical research centers across the country. Heart and lungs are usually treated as a unit because the connections between these two organs are so intricate that it is difficult to take one out of the blood circuit without the other. In principle these organs are relatively simple. The heart itself is a highly reliable pump, built to last a lifetime. The lungs are simply a device to expose the blood to air so that oxygen can be absorbed and carbon dioxide immediately released.
Actually, of course, nothing in the human body is simple. Commercial pumps are available that can handle blood without damaging or contaminating it, but they must be absolutely reliable. It would be highly desirable to have a pump that would automatically vary its rate of delivery to match the needs of the patient.
Building an efficient lung presents even greater problems. For the oxygen and carbon dioxide exchange to be carried out properly, as much blood surface as possible must be exposed to oxygen. Yet extreme care must be taken to keep the blood from carrying away bubbles of gas that might eventually lodge somewhere in the body with deadly results. For the same reason, the entire system must be designed to keep the blood from drying or clotting, producing equally fatal obstructions. And because the blood is a highly sensitive and complicated fluid, it must not be treated roughly, exposed to contamination, or allowed to touch any substance that might alter its structure.
Anti-foaming and anti-coagulant chemicals help solve some problems. Others are handled in a variety of ways in the machines now under development. A machine designed at the University of Minnesota, for example, uses a commercial pump for the heart, and a lung built of standard commercial plastic tubing. Moving up a vertical tube through which oxygen is bubbled, the blood absorbs the oxygen, then proceeds into a larger chamber where it meets an anti-foamant. Next the blood runs down a spiral coil. Here any remaining bubbles disappear as the unabsorbed gas travels upward. Since the whole lung system costs less than $15, it can be discarded after a single use
—a great advantage because decontamination after use is difficult.
A machine built at Cedars of Lebanon Hospital at Los Angeles uses quite a different kind of lung. The blood is dripped into a vat that contains a froth of blood and oxygen, formed by bubbling oxygen through a, blood reservoir. Here the gas exchange takes place. On the way back to the heart, the blood passes through a bubble trap of curved plastic tubing, providing a large exposed surface so that the bubbles can rise to the surface and escape.
A third lung is found in a machine produced at the College of Medicine of the State University of New York in Brooklyn. Perforated stainless steel disks revolve slowly — driven by an electric motor — around a horizontal axis. Blood flows from the patient to the center of the disks by gravity, minimizing risk of pulling air bubbles into the bloodstream. As the blood is spread out across the disks by centrifugal force, it meets a high-oxygen atmosphere created by drawing oxygen from a reservoir. The blood picks up some of this oxygen. At the bottom of the disks the oxygenated blood drips off and passes through a stainless steel sponge coated with anti-foamant to remove bubbles.
To see one of these machines in use, even with a canine patient, is a remarkable experience. The subject is anesthetized, the chest opened swiftly, the heart’s pumping action halted with a slight electric shock, the machine quickly connected. Dark blood, deficient in oxygen and heavy with carbon dioxide, runs down the tubing to the machine, set on the floor. As it reaches the shining stainless steel disks, it spreads out across them, turning bright red as it picks up oxygen. It then flows by gravity to two small transparent plastic pumps. In each of these, compressed air pushes up a rubber diaphragm, forcing the blood uphill and into the body’s circulatory system.
Since there is no vacuum in this type of pump, atmospheric air cannot be sucked in through the tubing, as sometimes happens with ordinary pumps. When the surgery is completed and the heart reconnected, another shock starts the heart pumping once more. (Stopping the heart beat is done only in certain types of operations, where cardiac action would interfere. Some other research groups are producing cardiac standstill by injection of certain chemicals into the coronary artery circulation.)
A variety of heart-lung machines are already being used successfully with human patients. They can give overtaxed hearts a chance to recuperate, for several hours if necessary. There are many conditions in which such a rest can be invaluable. Use of the machines makes it possible for the surgeon to see exactly what he is doing, freeing him from the need to work in an ocean of blood when he opens the heart. Most important of all, the machines give him time. The limiting factor in surgical repair of the heart is the extremely short period the body can survive while the blood circulation is halted. If circulation must be cut off from all of the body except the brain, the surgeon has about 34 minutes to complete his job. This is little enough, but if he wishes to work at a point where the blood flow to the brain itself is cut off, the surgeon has only 3½ minutes. After that, lack of oxygen does irreparable damage to the brain cells.
When a heart-lung machine keeps the blood in circulation to brain and body alike, these spans can be greatly prolonged. The surgeon has time to do delicate repairs to the heart itself, correcting congenital defects or damage done by disease.
These machines may eventually permit the safe repair of coronary artery disease. (The technique for obtaining blood pressure readings and blood analysis from the heart itself — for which the Nobel prize in medicine was awarded this fall — plays a vital part in helping the surgeon to decide when advanced heart surgery is necessary.)
There is every likelihood that it will be possible to replace essential portions of the heart and its great vessels. Studies are in process using both human materials — preserved by freezing and drying — and such man-made materials as nylon and orlon. At the Surgical Research Laboratory, State University of New York, a dog lived for months with a plastic ball valve in place of an important heart valve. His chest emitted a steady click-click, like Barrie’s crocodile.
Today’s heart-lung machines are bulky and delicate, but the technological skills that produced miniature radios and computers from their unwieldy prototypes of a generation or so ago should be equally successful in miniaturizing artificial organs. If so, medicine will once again owe a debt to the engineer. The New Jersey State Medical Society Journal pointed out not long ago that collaboration between doctors and engineers is inevitable and essential: “The first group to build a bridge between the two professions will make an enormous contribution to human progress.
. . . To be sure the body is not just a machine. . . . But there is enough of the machine in the human body to need the help of an engineer.”
At Australian airports a vehicle that looks like a triple cross between a bus, a fire engine, and a tank stands ready to rescue persons trapped in crashed aircraft. Its engine is mounted in the rear, and it shoots a pathway of foam as it rolls to the wreck. There a circular saw set into the tender’s bow takes three seconds to cut a 2½foot escape hole, while two huge asbestos blankets swing out to shield the occupants as they crawl out.
Rescue workers can also enter the plane with a portable saw to cut free persons caught inside. An inch and a half of rock wool between two steel walls protects the occupants of the tender from a half hour of 600-degree exterior temperature. Windows are made of heat-resistant glass and are steel-shuttered.
Automatic radio station
An automatic control system for radio stations makes it possible to program an entire day’s broadcasting in a couple of hours, flip a switch, and go off to the races. Unattended, the station will run through fourteen hours of commercials, records, station breaks, taped interviews, and other transcriptions.
The heart of the Autostation — made by Gates—is a special magnetic tape, which carries two sets of signals side by side. Half the tape records commercials and other announcements, while the strip beside it carries a series of tone signals. These signals are never translated into sound; instead they turn on and off other electronic equipment such as record players and tape recorders. The tape stops when the record player starts, picks up again when record or transcription stops, Tone signals of different frequencies can be used to bring any number of players or tape recorders in on cue.
One hazard of highway building may be a shower of complaints about broken windows and cracked crockery. Estimating the effect of a blast on the surrounding neighborhood is an art that requires great skill and experience. Now a device called the Aecelerograph, something like a baby seismograph, is turning this art into a science by measuring test blasts.
The Accelerograph is placed on solid ground or rock a given number of feet away from where a test blast is to be made. Three thin reeds inside the instrument, one for motion in each of three planes, pick up the shock waves and agitate a light beam that records a wavy line on moving 70-mm. film.
Analyzing the size and character of the vibrations on the film, engineers can determine the exact amount of explosive that will do the job at that site without shaking the surrounding area. Developed by the Liberty Mutual Insurance Company, the device also makes a permanent record that can be produced in court to refute false damage claims.