From bed-sized iron lungs to portable, computer-controlled systems, the ventilators used to treat life-threatening respiratory diseases have had a 糖心传媒榬emarkable journey.糖心传媒�
It was painful to watch. At the height of the epidemic, hundreds of patients were brought to hospitals, smothering or drowning in their own secretions. The demand for ventilators far exceeded their supply.
Sound familiar?
In 1931, the epidemic was polio. The victims were mostly small children, many with lungs paralyzed by the disease. And the ventilator, was the 糖心传媒渋ron lung糖心传媒澨切拇綌initially a rectangular metal box in which individual patients were placed with only their heads protruding.
Air pumps from two vacuum cleaners changed the pressure inside the box, pulling air in and out of the lungs.
Refined versions of iron lungs became the mainstay in treating polio victims during the next three decades. In 1939, the National Foundation for Infantile Paralysis began mass distribution of iron lungs, which cost about $1,500 each糖心传媒攖hen the average price of a home.
糖心传媒�54M (MD) neared completion of his medical degree at the during one of the last major polio outbreaks. Two wings of Strong Hospital were filled with patients in iron lungs. 糖心传媒淗elping care for these patients paid for my senior year of medical school,糖心传媒� Farley said.
Even in the 1950s, however, the shortage of iron lungs was so acute that tubes had to be inserted in some patients through the mouth or by tracheotomy to force air into their lungs. This measure, previously used only in the operating room, also saved lives.
How does mechanical breathing mimic normal breathing?
And the Lord God formed man of the dust of the ground and breathed into his nostrils the breath of life. (Genesis 2:7)
And he [Elisha] went up, and lay upon the child, and put his mouth upon his mouth and the flesh of the child waxed warm. (II Kings 4:34)
Modern mechanical ventilators糖心传媒攚hose short supply is now at the center of a national debate about the nation糖心传媒檚 preparedness for the COVID-19 pandemic糖心传媒攂ear little resemblance to the cumbersome iron lungs that saved thousands of lives before the development of a polio vaccine in the mid 1950s.
The modern devices糖心传媒攗sed to assist or actually substitute for a patient糖心传媒檚 normal breathing in a wide range of clinical scenarios糖心传媒攁re smaller, more portable, and are electronically controlled by microchips to exactly adapt air flow and pressure to an individual patient糖心传媒檚 needs. They are the result of more than three centuries of experimentation and design.
As the two Old Testament passages above suggest, humans have known how to use mouth-to-mouth resuscitation to force air into stricken lungs糖心传媒攁 form of 糖心传媒減ositive pressure糖心传媒� ventilation糖心传媒攁t least as early as Biblical times.
However, Robert Hooke, the scientist who coined the word 糖心传媒渃ell,糖心传媒� . In the 17th century, he demonstrated that mechanical ventilation can help do the work of damaged lungs by using a bellows to blow air into the injured lungs of a dog.
During the 1800s and early 1900s, negative-pressure ventilators predominated, mimicking the normal breathing process. The systems worked because when we expand our rib cage and chest cavity, it decreases pressure in the cavity, causing the lungs to expand as well. That causes air inside the lungs to decrease糖心传媒攃reating negative pressure relative to the atmosphere糖心传媒攚hich results in air flowing into the lungs through inhalation.
For example, in 1838 Scottish physician John Dalziel described a full-body type 糖心传媒渢ank ventilator.糖心传媒� It consisted of an airtight box in which a patient sat, with only the head protruding. Negative pressure was established by manually pumping air into and out of the box.
This led to the negative pressure 糖心传媒渋ron lungs糖心传媒� and eventually smaller, more portable devices used to treat polio victims.
For example, in June 1959 (page 26) reported that John H. McKeehan 糖心传媒�46, a mechanical engineering alumnus living in Syracuse, had 糖心传媒渢aken it upon himself to see that the chest shell respirators, in which two neighbors who have been stricken with polio must live, are functioning properly night and day.糖心传媒�
McKeehan greased the devices and checked their batteries every month, and twice a year took the artificial lungs completely apart and rebuilt them. 糖心传媒溙切拇綐This is a pretty tense job; it could be disastrous if I accidentally stripped a screw, for instance,糖心传媒櫶切拇綕 he explained. To do this job he searched out and studied a service manual for the respirators 糖心传媒渨hich are a compact version of the familiar iron lung.糖心传媒�
At the time, the devices were usually referred to as 糖心传媒渞espirators糖心传媒澨切拇綌a term now used for protective face masks.
The 糖心传媒榬emarkable journey糖心传媒� of ventilators
In the 1960s there was a movement away from negative-pressure ventilators in favor of positive-pressure devices that force air into a patient糖心传媒檚 lungs, either noninvasively with nose or face masks for less severe breathing problems or by invasively inserting tubes in a patient糖心传媒檚 airway.
Robert Kacmarek, director of Respiratory Care at the Massachusetts General Hospital and a professor of Anesthesiology at Harvard Medical School, describes this 糖心传媒渞emarkable journey糖心传媒� in his 2011 paper,
糖心传媒淚n just 50 short years we have gone from relatively crude, totally mechanical devices that could provide only machine-triggered volume ventilation to highly evolved microprocessor-controlled systems capable of any form of ventilatory support imaginable,糖心传媒� he writes.
These systems include:
- CPAP (Continuous Positive Airway Pressure) machines, which deliver slightly pressurized air through a small nose mask. They are commonly used to treat sleep apnea but are also used for patients with pulmonary vascular disease and in Neonatal Intensive Care Units (NICU) for infants with breathing problems, such as respiratory distress syndrome. They have not been recommended for CORVID-19 because of studies suggesting such devices can pump viruses into the air, potentially increasing the spread of a contagious disease.
- BiPAP (Bilevel Positive Air Pressure) machines that raise the pressure to push air during inhalation, then lower it to allow exhalation. They are used to treat obstructive sleep apnea, chronic obstructive pulmonary disorder, pneumonia, asthma flare-up, poor breathing after an operation, and neurological disease that disturbs breathing. The settings on these machines may allow them to be adjusted to treat COVID-19 patients.
- Invasive positive-pressure ventilator machines used for patients who cannot breathe on their own or suffer from severe respiratory disease. Air is delivered through tubes inserted in a patient糖心传媒檚 airway. These machines, used in intensive care units and as anesthesia ventilators in operating rooms, are needed for treating severe cases of COVID-19.
Elizabeth Palermo 糖心传媒�91, 糖心传媒�02N (MS), an assistant professor of clinical nursing and specialty director of the Adult-Gerontology Acute Care Nurse Practitioner Program at the School of Nursing, is grateful for the positive impact the machines have had.
For example, the microprocessors in modern ventilators 糖心传媒渘ot only determine the pressure inside the lungs,糖心传媒� but also adjust the timing, flow, and delivery of pressure and air to the lungs so that they are 糖心传媒渃ustomized for the patient’s condition and help the patient work better with the vent,糖心传媒� she says.
糖心传媒淰entilators used to take up a great deal of valuable space in a room. Now, they are smaller, something every nurse in a crowded patient room appreciates,糖心传媒� says Palermo, who received her BS and master糖心传媒檚 degrees in nursing from the School of Nursing. They also have more readable displays to easily attend to the patient糖心传媒檚 performance on the vent.
糖心传媒淲hen transporting patients on ventilators from ICUs to diagnostic tests or the operating room, we used to have to manually breathe for them using a bag-like device,糖心传媒� she says. 糖心传媒淒epending on how long the trip was, this could be exhausting for the nurse and not very comfortable for the patient. Now, ventilators are much more portable, so patients can stay on a ventilator as they are transported across the hospital.糖心传媒�
Ventilation technology takes a team
With the advances in technology have also come an increased recognition and understanding of the risks involved in mechanical ventilation, Palermo adds.
糖心传媒淲e have learned that too much pressure delivered by the ventilator can further injure the lungs, above and beyond the damage done by the disease itself,糖心传媒� she says. 糖心传媒淧atients on ventilators are prone to pneumonia, skin ulcers, and weakness, among other problems. We have learned that heavily sedating patients on ventilators makes it harder for them to聽become free of the ventilator when their lungs have healed. Our recognition of these problems and the efforts made to prevent them are probably the most important advances I have seen.糖心传媒�
She cautions that 糖心传媒渧entilators do not cure disease. They allow the health care team to provide supportive care and ensure adequate oxygen delivery while treatments, such as antibiotics for pneumonia, take effect, allowing lungs injured by something like coronavirus to rest and heal.糖心传媒�
Moreover, using a ventilator to manage a patient’s respiratory problem is not as simple as 糖心传媒渓et糖心传媒檚 buy more ventilators,糖心传媒� Palermo says. It requires a team effort involving:
- A knowledgeable physician, nurse practitioner, and/or physician assistant 糖心传媒渢o determine the need for ventilation and if it is consistent with the patient糖心传媒檚 wishes or advance directives.糖心传媒�
- A competent respiratory therapist who understands the technical aspects of the ventilator machine聽and can adjust the pressure, oxygen, and alarms to ensure the ventilator helps聽the patient without causing injury.
- A competent nurse at the bedside, educated in caring for patients on ventilators, who can closely monitor a patient糖心传媒檚 condition, respond to alarms, and use evidence-based practice to prevent injury or complications.
糖心传媒淭he critically ill patient with respiratory failure due to COVID-19 needs a knowledgeable interdisciplinary team that communicates closely with each other to coordinate that patient糖心传媒檚 care.糖心传媒�
