iron lung

An Emerson iron lung. The patient lies within the chamber, which when sealed provides an effectively oscillating atmospheric pressure. This particular machine was donated to the Centers for Disease Control and Prevention Museum by the family of polio patient Barton Hebert of Covington, Louisiana, who had used the device from the late 1950s until his death in 2003.

An iron lung is a machine that enables a person to breathe when normal muscle control has been lost or the work of breathing exceeds the person's ability. It is a form of medical ventilator. Properly, it is called a negative pressure ventilator.

Method and use

Humans, like many other animals, breathe by negative pressure breathing:^[1] the rib cage expands and the diaphragm pulls down, expanding the chest cavity. This causes the pressure in the chest cavity to decrease, and the lungs expand to fill the space. This, in turn, causes the pressure of the air inside the lungs to fall (it becomes negative, relative to the atmosphere), and air flows into the lungs from the atmosphere: inhalation. When the chest cavity is contracted, the reverse happens and the person exhales. If a person loses part or all of the ability to control the muscles involved, breathing becomes difficult or impossible.

Iron lung ward filled with polio patients, Rancho Los Amigos Hospital, California (1953)

The person using the iron lung is placed into the central chamber, a cylindrical steel drum. A door allowing the head and neck to remain free is then closed, forming a sealed, air-tight compartment enclosing the rest of the person's body. Pumps that control airflow periodically decrease and increase the air pressure within the chamber, and particularly, on the chest. When the pressure is below that within the lungs, the lungs expand and atmospheric pressure pushes air from outside the chamber in via the person's nose and airways to keep the lungs filled; when the pressure goes above that within the lungs, the reverse occurs, and air is expelled. In this manner, the iron lung mimics the physiological action of breathing: by periodically altering intrathoracic pressure, it causes air to flow in and out of the lungs. The iron lung is a form of non-invasive therapy.

Invention and progression

An iron lung in use (1960)

The machine was invented by Phillip Drinker and Louis Agassiz Shaw. Originally for treatment of coal gas poisoning, it found its most famous use in the mid-1900s when victims of poliomyelitis (more commonly known as polio), stricken with paralysis (including of the diaphragm, the cone shaped muscle at the bottom of the rib-cage whose action controls intrathoracic pressure), became unable to breathe, and were placed in these steel chambers to survive. The first iron lung was used on October 12, 1928 at Children's Hospital, Boston, on a child unconscious from respiratory failure; her dramatic recovery, within seconds of being placed within the chamber, did much to popularize the "Drinker Respirator."^[2] Boston manufacturer Warren E. Collins began production of the iron lung that year.^[3]

In 1931, inveterate tinkerer John Haven "Jack" Emerson unveiled a less expensive iron lung.^[4] Drinker and Harvard promptly sued Emerson for patent violations, which proved unwise. In the subsequent legal battles Emerson demonstrated that every aspect of Drinker's patents had been patented by others at earlier times. Emerson won the case, and Drinker's patents were declared invalid.

Entire hospital wards were filled with rows of iron lungs at the height of the polio outbreaks of the 1940s and 1950s. With the success of the worldwide polio vaccination programs which have virtually eradicated new cases of the disease, and the advent of modern ventilators that control breathing via the direct intubation of the airway, the use of the iron lung has sharply declined.

Modern usage

Patient in the tank of a modern negative pressure ventilator. The tank has a clear acrylic lid and a gasket around the patient's neck. The ventilator itself is the small box in front.

Positive pressure ventilation systems are now more common than negative pressure systems. Positive pressure ventilators work by blowing air into the patient's lungs via intubation through the airway; they were used for the first time in Blegdams Hospital, Copenhagen, Denmark during a polio outbreak in 1952.^[5] It proved a success and soon superseded the iron lung throughout Europe.

The iron lung now has a marginal place in modern respiratory therapy. Most patients with paralysis of the breathing muscles use modern mechanical ventilators that push air into the airway with positive pressure. These are generally efficacious and have the advantage of not restricting patients' movements or caregivers' ability to examine the patients as significantly as an iron lung does. However, negative pressure ventilation is a truer approximation of normal physiological breathing and results in more normal distribution of air in the lungs. It may also be preferable in certain rare conditions, such as Ondine's curse, in which failure of the medullary respiratory centers at the base of the brain result in patients having no autonomic control of breathing. At least one reported polio patient, Dianne Odell, had a spinal deformity that caused the use of mechanical ventilators to be contraindicated.^[6] Thus, there are patients who today still use the older machines, often in their homes, despite the occasional difficulty of finding the various replacement parts. Joan Headley of Post-Polio Health International stated to CNN that there are approximately 30 patients in the USA still using an iron lung.^[7] That figure may be low; Houston alone had 19 Iron Lung patients living at home in 2008.^[8] Martha Mason of Lattimore, North Carolina died on May 4, 2009, after spending 60 of her 71 years in an iron lung.^[9]

On the 30th of October 2009, June Middleton, an Australian woman who entered the Guinness book of records as the person who spent the longest time in an iron lung died aged 83 in Melbourne, Australia. ^[10]

Biphasic Cuirass Ventilation is a modern development of the iron lung, consisting of a wearable rigid upper-body shell (a cuirass) which functions as a negative pressure ventilator.

Literature

• Martha Mason, a polio survivor, penned a best-selling memoir, Breath, about her life inside an iron lung.
• June Opie describes her time in an iron lung during recovery from polio, in her novel Over My Dead Body"
• Jacob Appel's story "Long Term" addresses the disposal of iron lungs after their occupants have died.^[11]
• Margaret Atwood mentions an iron lung in her book Cat's Eye
• Peg Kehret mentions her use of an iron lung in her autobiographical book, Small Steps: The Year I Got Polio

References