In the 1920s experiments were being made on anaesthetized cats to record the positive pressure changes caused by inspiration in an enclosed chamber around the animal's thorax. The investigator's colleague, Dr Philip Drinker of the Harvard School of Public Health, acutely aware of the clinical problem at the nearby Children's Hospital, of respiratory failure in infantile paralysis, repeated the experiment with cats paralysed with curare. He found that animal could be ventilated and kept alive by the suction action of a syringe attached to the box enclosing the animal's body. Drinker sought and obtained funding from the Consolidated Gas Company of New York (who had previously sponsored a committee chaired by Drinker, which reported on improved methods of resuscitation in cases of gaseous poisoning), and with Louis Shaw he built a wooden cabinet, which opened and shut like a drawer, to contain the human torso.
In 1926 his first iron lung (perhaps named for the iron of the pump) was left at the bedside of an eight-year-old girl affected with respiratory paralysis due to polio. As she deteriorated she was placed in the cabinet, but the staff, unfamiliar with the device, feared to turn on the pump, which was left to Drinker himself. Within minutes the moribund young girl was revived, only to die soon after of pneumonia.
Thus it had been established that artificial respiration could maintain life, but little was known of the natural history of such respiratory paralysis. Would this mean the prospect of an entire lifetime in an iron lung? Although this was the case for some, the second patient to be treated, at the adjoining Peter Bent Brigham Hospital, recovered respiratory muscle function, and the era of life-support was begun.
In the 1930s, ‘Drinkers’ as they also became known, were found throughout the US; in the UK a cheaper alternative, designed by Both, an Australian, was also available, being paid for by the motor car manufacturer and philanthropist Lord Nuffield. By 1937, 965 of these were to be found throughout the UK and elsewhere. Improved access for patients was achieved with a hinged opening of the tank, like the jaws of an alligator (or Alligator tank) this time by Captain Smith-Clarke of the Alvis Motor Car Company. Cape Engineering company produced aluminum versions, of which 150 were sold between 1954 and 1967. An additional modification was introduced in 1961 by Dr W. Howlett Kelleher of the Artificial Respiration Unit at the, Western Hospital, Fulham. This was a rotating version of the Iron Lung, which permitted chest physiotherapy in all positions.
The non-invasive application of positive pressure through nose masks has largely superceded the iron lung in the treatment of respiratory failure, but the final chapter in the story of the iron lung is still to be written. In the UK a few patients remain ventilated for part or all of the day using the iron lung, and it is still used by some in the short term for people with acute exacerbations of chronic airways obstruction.
Adrian J. Williams
See also artificial ventilation; breathing; resuscitation.
Iron Lung and Other Respirators
Iron lung and other respirators
The iron lung was invented in 1929 by Philip Drinker (1893-1977), a professor at the School of Public Health at Harvard University. The device performs the function of the muscles that control breathing. It was one of the first of several inventions designed to keep people alive who are unable to breathe unassisted.
During the 1920s people who could not breathe on their own were aided by a pulmotor. This was a machine similar to fireplace bellows. It inflated and deflated the lungs by forcing air in and then sucking it back out again. The process worked, but some patients experienced chest pain. Many people suffering from polio or infantile paralysis required such a device. The polio virus can damage the nervous system causing paralysis of the diaphragm. Without the movement of the diaphragm, polio-sufferers often died by suffocation.
Drinker got his idea from a Swedish physician named Thunberg, who had been experimenting with a vacuum device to help patients breathe. Drinker enlisted the help of his brother, Cecil, and Louis Shaw (1886-1940) to build a prototype (model) based on Thunberg's principles. He tested the first machine on cats and then designed one large enough for a human patient.
The patient's head was positioned outside the box while the rest of the body was enclosed in the airtight metal box. A pump connected to the box varied the air pressure inside the chamber. When the air pressure inside the box decreased, the weight of the atmosphere outside the box forced air through the nose and mouth into the lungs. When the air pressure in the box increased, the air was forced out of the lungs.
Drinker's invention was first known as the "Drinker tank respirator" but was soon given the nickname of "iron lung." Drinker and Louis Shaw received numerous awards for their invention. The iron lung allowed many polio patients to live longer lives. It was used from 1928 well into the 1950s.
Since Drinker's time, a sophisticated class of breathing machines called ventilators, or respirators, has been developed. A modern ventilator consists of an electrical pump connected to an air supply, a humidifier that adds water to the air, and a tube inserted into the patient's nose or mouth. Ventilators use positive air pressure from the pump to force air into the lungs. The ventilator pumps air into the lungs for a preset time or volume and then stops. The patient then exhales the air naturally.
To adjust the ventilator properly, a blood sample from the patient is analyzed. This determines the metabolic rate and the optimal oxygen-carbon dioxide ratio. Then the volume of air needed and the number of times per minute the person should breathe to maintain the desired metabolic rate is calculated. When properly connected, positive air pressure brings just the right volume of air into the lungs. Then the lungs passively deflate when the ventilator shops filling the lungs. Today's sophisticated hospital respiratory care units may utilize up to 15 different kinds of respirators.
Ventilators aid patients who have paralyzed muscles, suffer from degenerative muscle disease, or have burns in the nose and throat. When patients are to be hooked up to a ventilator for months at a time a breathing tube is surgically inserted directly into the windpipe. Miniature ventilators are used to help premature babies breathe. They are also used to help patients who have undergone surgery and need temporary help from a machine.
In some places, the iron lung of the 1950s is making a comeback. Because it uses non-invasive technology and negative air pressure (a vacuum), it does not cause infections or scarring of the trachea. It can be used at home to help a patient rest the respiratory muscles during the day or night.
Mini-iron lungs are now used for some patients. Nicknamed "turtles" because of their green color and shell-like shape, these miniature devices can be strapped onto a patient's chest.
i·ron lung • n. a rigid case fitted over a patient's body, used for administering prolonged artificial respiration by means of mechanical pumps.