Respiratory Therapy History Timeline

Compared to physicians, who can trace their roots to ancient times, and nurses, who can trace their roots to Clara Barton's Civil War heroics, the profession of respiratory therapy is a relatively young profession that can be traced only as far back as 1922.

We could trace it back to 5,000 B.C. when Egyptians inhale smoke from dried and crushed herbs burned on heated bricks to get breathing relief, or 100 A.D. when in India herbs were smoked in pipes, or even the 19th century when the first nebulizers were patented.

Yet the profession as we know it can only be traced back to 1922 when John Scott Haldane wrote about his research on oxygen in "The Therapeutic Administration of Oxygen."  It was this book that sparked interest in the therapeutic use in oxygen to treat diseases.

One of the first people to gain interest in attempting to create some sort of effective device for delivering therapeutic oxygen to patients was Dr. Leonard Hill of England.  In 1921 he announced his invention of an oxygen tent capable of delivering approximately 30 percnet oxygen.  It consisted of an airtight canopy that covered the patient and the bed.  (1) 

A major problem with these tents is they had no methods of controlling humidity and temperature, and patient's would become very uncomfortable inside them.  However, patients who needed supplemental oxygen to breathe would request the tent be taken down, and as soon as their breathing became labored again they'd request to be back inside.  So it was sort of a double edgled sword for these patients. 

In 1926 Alvin Barach invented an oxygen tent blew air over ice chips to cool the temperature inside the tent.  This made it so being inside the tents were much more bareable.   Usually these tents were reserved to patients with pneumonia and heart failure. (2) In 1931 John Emerson invented an oxygen tent that had a cooling system.  Preious devices were prone to rust and failure.  His cooling mechanism was  also ice.  (3)

In 1928 the Shaw respirator was introduced to the market.  This was the first electric and mass produceable negative pressure ventilator.  It was large, very expensive, noisy, and very heavy.  Yet it soon became very useful in keeping patients inflicted with polio and other such disorders that caused a person to stop breathing alive.  These ventilators, referred to as the tank or iron lung, were improved by John Haven Emerson, and in 1931 he introduced the Emerson Respirator.  Emerson's design was simpler, quieter, and had a method of manually breathing for the patinet should their be a power outage. Emerson's respirator would quickly become the most common iron lung used in hospitals in the U.S. and Europe. 

Nurses were initially responsible for oxygen equipment during the 1920s, and doctors and their technitians were initially responsible for setting up and manageing the iron lungs.  Yet lugging heavy oxygen tanks into rooms, and monitoring how much oxygen was in them, remained the task of the nurses.  Since the gauges were primitive, nurses would have to use formulas to calculate how long the tank of oxygen would last, and would have to switch tanks before they became empty. 

Complicating matters was that along with performing their nursing duties they also had to manage the oxygen tents and, eventually, iron lungs.  Their were a variety of gauges on the iron lungs that had to be monitored, along with making sure oxygen tanks used were likewise constantly full of oxygen.  To make matters worse, the gauges used were known to be innacurate (4)

Oxygen masks are designed by John Haldane and others, and are made of leather.  The first non-rebreather masks are fitted with vinyl bags for storing excess oxygen to be rebretahed, and had two one way valves, one on each side of the mask, to prevent air entrainment.  These masks at times turned out to be deadly when an oxygen tank ran empty.  And since the leather masks fit snug over the patient's face unlike modern plastic masks, one of the flaps would ultimately be required to be removed in order to prevent accidental asphyxiation.  This is the reason one of the flaps is missing on modern non-rebreathers. 

Vinyl nasal catheters were also designed by Haldane.  To humidify oxygen glass and metal humidifiers were invented.  Nebulizers were also made of glass, although until the 1930s a bulb had to be used to cause the medicine to turn into an aerosolized mist.  In the 1930s an electric nebulizer was invented and was mass produced that made for breathing treatments to become easy and more effective.  It became the job of nurses to administer such breathing treatments.  It was their job also to clean all this equipment between patients. 

By the 1940s nursing assistants are recruited to set up, monitor, and clean oxygen equipment.  They are ultimately referred to as inhalation tharapits and also pick up the task of doing the same for iron lungs and other respiratory equipment.  These first inhalation therapis are generally trained on the job, often referred to as OJTs (on the job training) and are usually poorly educated about what they were doing.  It was for this reason that an organization called the Inhalation Therapy Association was created in 1946 to form a means of educating inhalation therapists and further improving credentials and respect for the new profession.  The name was changed a few more times until it's current name of the American Associatino of Respiratory Care (AARC). 

By the 1930s oxygen is beginning to be piped into hospitals, and this continues during the 1940s.  For a while there is a fear that the profession will become to an end, as most inhalation therapits, now referred to as respiratory therapists, are often referred to as tank jockeys.  Yet the profession would evolve into more than just oxygen as in 1952 the first intermittent positive breathing machines become available.  These machines would at first be used to ventilate patients for short periods of time either via a rubber mask or cannula inserted into a tracheostomy.  Their are a variety of IPPB machines to hit the market, yet the most common are the Bennet PR 1 and 2, and by 1955 the Bird Mark 7. 

These machines were used as ventilators until the late 1950s and early 1960s until they and the iron lungs were ultimately replaced by more effective volume ventilators, the most popular of which were the Emerson Volume Ventilator that hit the market in 1964 and the MA1 that hit the market in 1967.  The Emerson ventilator was often referred to as a big green washing machine.  The MA1 was such a sturdy and compact unit that it was still around in 1997 when I became an RT at my present location. 

Monitoring and maintaining these machines was a complicated job, and respiratory therapists were needed.  While oxygen equipment became simpler over time, respiratory therapists were still required to monitor it's use, set it up, and clean it between patients.  RTs were also needed to do IPPB treatments.  During the early 1950s it became a common belief that giving aerosolized medicine, such as bronchodilators, by an IPPB machine three to four times per day would force the medicine deeper into the lungs.  This type of therapy was also believed to open collapsed alveoli and improve atelectic lungs in post operative patients.  It was also believed to prevent atelectasis.  For this reason, IPPB therapy became very common in hospitals and was ultimately used for more than just post operative patient.  It was used for COPD patients, asthma patients, and patients with just about any other lung disorder.  RTs were needed to do all this.

It was also during the late 1940s and 1950s that observations were made about COPD patients becoming lethargic and even dying due to exposure to too much oxygen.  This gave birth to the hypoxic drive theory whereby it was believed some COPD patients who were chornic CO2 retainers no longer used CO2 as their drive to breathe and instead used oxygen.  For this reason, it was believed that  too much oxygen would knock out their drive to breathe.  This was ultimately proven by Dr. E.J.M. Campbell in the 1950s based on a study of only four COPD patients.  In a report to the physicians in 1960 he reported his findings, and ever since doctors have been taught the hypoxic drive theory. 

The hypoxic drive theory is significant in that it was another reason for the importance of respiratory therapist monitoring oxygen therapy.  As therapist obtained more and more responsibility, it was realized the scope of knowledge needed for these individuals far exceeded their education and training.  This was particularly apparent on the weekends and night shifts when the least experiences therapists were working alone. (5)

By the 1960s most respiratory therapists have to study and take a test to work in the field, and this put an end to on the job training.  The first tests are oral, although eventually the written tests are created.  This also put an end to respiratory therapist being an ancillary staff, and instead RTs became a respected part of the patient care team. 

In these early days most respiratory procedures were profitable.  Many believe this was one of the reason so many IPPB therapies were ordered during the 1950s and 1960s.  Yet during the 1970s insurance companies started questioning the need for all these IPPB treatments.  Studies performed proved that nebulized aerosols provided better distribution of medicine into the lungs that IPPBs, as much as 35% better distribution.  Other studies proved that insentive spirometry was more effective than IPPBs in preventing and treating post operative atelectatis.  So IPPB therapy in this way started to decline.  However, it would be until the turn of the 21st century that most Bird Mark 7s would be bound and tied in the basements or sent to foreign countires or simply jettisoned into the trash pit.  These machines were durable, and my hospital still has one that doctors still put into use even to this day. 

In 1983 DRGs are created, and hospitals no longer get reimbursed for each procedure performed.  For this reason, many RTs fear their jobs will be eliminated. Instead, hospitals would be paid a flat fee for each patient.  In this way it was believed that hospitals would do as few procedures as possible when taking care of a patient.  Thus, it was thought DRGs would reduce hospital costs.  Yet the exact opposite happened.  In order to meet reimbursement criteria, many doctors simply diagnosed patients with diseases they thought were the most reimbursable, such as pneumonia, asthma, cardiac failure and COPD.  Perhaps it's for this reason, or just a coincidence, that asthma rates have skyrocketed since 1980. 

Since 1980 IPPB therapy has seen a decline, but aerosol therapy has seen a incline.  Doctors now order breathing treatments instead of IPPB therapy for all lung ailments.  In many cases, breathing treatments are ordered so the patient or family member thinks something is being done to make sure the patient or family doesn't sue the doctor.  Breathing treatments are also often ordered as part of order sets that make sure everything is ordered that may be needed for the patient to meet government set criteria for reimbursement.  This has all resulted in an exhorbitant amount of breathing treatments being ordered, and this has helped many RTs to continue to work.

Yet many hospitals have added protocols that allow the therapist to use his education and skills to only provide those services that are necessary and proven to work.  Many hospitals allow RTs driven protocols that allow RTs to decide who should get breathing treatments, and other protocols allow for RTs to decide what oxygen device to use, and what ventilator settings to use.  Many hospitals also have ventilator weaning and extubation protocols, and, of course, respiratory therapists are a major part of the hospital's critical care team responsible for attending all code blues, or instances where a patient doesn't look quite right, has severe difficulty breathing, or goes into cardiac or cardiopulmonary arrest. 

There are a miraid of responsibilities for today's respiratory therapists.  A minimum of two years is now required to work in most RT settings.  The field is continueing to grow and gain respect.  Surely there is a ways to go, but since nursing has had an extra 60 years to evolve, it may take another 60 years for the profession of respiratory therapy to reach the full level of respece of the nursing profession.  Still there are obstacles to cross, yet the profesion will continue to be a necessary one for many years to come. 

References:

1.  "Questions and Answers," The Modesto Bee, Thursday, Dec. 2, 1948
2. Glover, Dennis W., "The History of Respiratory Therapy," 2010, page 40
3. Branson, Richard D, "Jack Emerson:  Notes on his life and contributions to Respiratory Care," Respiratory Care, July 1998, vol. 43, no. 7, pages 567-71
4. Glover, ibid, page 48
5. Wyka, Kenneth A, Paul Joseph Mathews, William F. Clark, "Fundamentals of Respiratory Care," 2001, page 10, "The Late 1950s and 1960s: Organizational and Clinical Maturation."

1980-2012: Evolution of Artificial Respiration

1980s: Down's Flow Generator:  Continuous Positive Airway Pressure, something that was researche in the 1930s but basically ignored as the iron lung was the popular mode of ventilating patients, made a comeback in the 1980s as studies showed it was effective in treating patients with COPD and sleep apnea.  The most common method of delivering CPAP in the hospital setting was with a Down's Flow Generator. The device was plugged into a wall oxygen outlet and hooked up to wide bore tubing.  The tubing was connected to a face mask that was securely strapped to the patient's face.  A pressure manometer is attached to the mask and an oxygen analyzer is added to the circuit via a T-piece to monitor percent of oxygen delivered to the patient.  A venturi system allowed you to adjust the FiO2 delivered to the patient.  Studies show a CPAP of 7.5 increases the partial pressure of alveolar air by 1 percent which is enough to force enough oxygen into the blood to make a clinical difference.  This was used until the mid to late 1990s when larger machines such as the Vision were determined to be more efficient deliverers of CPAP.  From my experience, CPAP is rarely ever used by itself in the hospital setting as BiPAP is usually preferred (see below).  However, when oxygen alone is the issue, CPAP may work just fine.  CPAP is, however, used as an effective means of weaning patients from ventilators, and thus is incorporated as a mode in most modern ventilators.  A downside to these generators is they didn't have any alarms.  A variety of CPAP generators are presently still available, such as the WhisperFlow generator which allows for contorl of flow and accurate FiO2s and various Caradyne Isobaric CPAP Valves to allow the clinician to adjust CPAP based on the patient's clinical condition. 

1983:  Puritan Bennett 7200

This was the first microprocessor ventilator to hit the market.  The machine was very durable and simple to use.  The settings were set by scrolling through an led screen, and alarms were set in the same way. It was easily used, portable, and worked well for the patient.  It quickly became the "most widely used ventilator around the world, capturing a 60 percent share of the international market by the end of the decade.  (c)

1987:   The Bird 6400ST

This ventilator was the first of the new generation of volume ventilators to hit the market.  It was a rectangular shaped ventilator with all your basic knobs on the front, including volume control, assist control, SIMV, PS and CPAP modes.  It also had a PEEP valve that was easily adjusted by a dial, and a full set of alarms.  The only knock on this simple device was the expiratory valves needed to be cleaned between each use and were a pain in the butt to put back together and keep in functioning order.  It was a very compact ventilator for its time.  We actually used this ventilator as either our main vent or back-up until about 2008.  

1991:  Servo 300 Ventilator

This was a replacement ventilator for the Servo 900 and was generally created to complete with the the Puritan Bennett 7200.  It was much simpler to use than the old 900 version, and therefore was less intimidating.

It had a new mode called Pressure Regulated Volume Control (PRVC) which made it so the patient could get a guaranteed volume, yet a sensor in the machine sensed changes in patient lung compliance to make sure the lowest pressure possible was given.  This is a ventilator that is still used where I work, although as a back up to the Servo i.

The ventilator also had an option called automode that allowed the patient to switch from a controlled rate (such as PRVC, or pressure control) to a patient driven mode (such as volume support or pressure support).  Many newer ventilators have their own version of PRVC and automode.

Another neat feature was it was one of the first ventilators that it provided the option of allowing either pressure or flowby to be used.  Before this all positive pressure ventilators sensed a patient breath as pressure was decreased when the patient inhaled.  Flowby is actually more sensitive in that all the patient has to do is inhale a small amount of flow and this is sensed by the machine.

 It also had a nice set up of graphics screen so you could see what the patient was doing and make adjustments accordingly.  This feature was nice because it allowed the patient to control the ventilator instead of the other way around.  It had a few flaws, yet it was a great ventilator.

It was also the first ventilator that could be adjusted so it could supply breaths to a patient of any age or size.  It was a good ventilator for newborns, pediatrics and adults. As you look at the entilator the what the patient was doing was lit up as red, and the ventilator settings were green.  So we'd often tell nurses:  "Green machine, red bed."  (d)

1992:  V.I.P. Bird Infant Pediatric System

It was referred to as the T-Bird ventilator. At the time it was also the first and only ventilator that was mobile.

1995:  BiPAP:  Noninvasive Positve Airway Pressure, sometimes referred to as simply Bilevel Positive Airway Pressure (which is a patented name but we often generic it), became common in the 1990s as another method of ventilating patients in a more non-invasive manner.  This is a means of providing support breaths with CPAP or PEEP, which is generally called end positive airway pressure (EPAP) on these machines.  Some of the initial models were crude and called for supplemental oxygen to be connected into the system, but new systems, such as the Vision, are touch screen, have flow and pressure waveforms, and allow the machines to be used pretty much like a ventilator.  The advantage is you can ventilate a patient and improve oxygenation without having to intubate the patient.  Masks can be removed for eating and drinking and taking medicine, and also oral care.  Studies show these machines work great for COPD, CHF and even some asthma patients.  They also work well for home use for patients with obstructive sleep apnea. Modern BiPAP machines are also more effective than the aforementioned down's flow generator in delivering CPAP, and the machines also allow for alarms and patient monitoring. 

2000:  Servo i, 840, Avea Ventilators

It has all the same features as the Sero 300 except that the flaws of the 300 have been corrected.  Instead of having all the dials on the front the settings are set by an easy to use touch screen.  The basic settings of rate, tital volume, and FiO2 could be set either this way or by quick access dials on the bottom of the screen.  The ventilator was also connected to a graphics screen for easy to see ventilator graphics.  (d)  Other similar ventilators include the Puritan-Bennett 840 and the Avea Ventilator.  These newer vents are microprocessor vents that include a variety of modes to improve patient comfort.  They also include waveforms to monitor the patient, and a variety of alarms.  Modern vents are also upgradeable. 

The future:  What will the future bring?  


References

1. (d)"About us:  History of Ventilation," maquet.com,  http://www.maquet.com/sectionPage.aspx?m1=112599762812&m2=112599885558&m3=112600545105&m4=112806653448&wsectionID=112806653448&languageID=4, accessed February 27, 2012

1700-1970: Evolution of intubation

How procedure was performed circa 1891 (23, page 20)

Curious physicians started investigating the human body during the course of the 18th century, and they learned a ton about human anatomy.  Near the end of the century physicians used this improved wisdom to discover and invent better methods of saving lives, such as intubation and bag mask ventilation.  

Such inventions were crude back then, and the methods of performing them must have been traumatic for the patients receiving them, yet they gave physicians something to work with in order to help their patients.  The more these physicians struggled, the better they got.  The more they tinkered, the better their equipment got.

Here is a pithy progression of some of the results that transpired due to the hard work, and crafty thinking, of a few admirable physicians.

1500:  A paralytic discovered for modern world:   Curare (Succicholine) was one of the most famous native American poison, as the Indians often placed it on the tips of their arrows in order to paralyze their prey.   (18, page 4, 177-178)  Sir Walter Raleigh first reported the paralytic when he discovered that the South American Tupi Indians used the poison on the tips of their hunting darts.  (19, page 1674)

1773:  First resuscitation of near drowning victim:  According to a 1920 publication by the Lungmotor Company, "Drowning: Historical-Statistical Methods of Resuscitation," "The first reliable history of a resuscitation from drowning was that performed by M. Reamer in Switzerland. This was reported to the French Academy of Sciences and translated into English by Dr. Crogan in 1773. About this time Dr. Fothergill published his "Physical Dissertation on Drowning," which was read before the Royal Society in England. In 1773, the first society for the rescue of those apparently drowned was instituted at Amsterdam, Holland."  (20, page 3) (22, page 1)

1774:  Humane Society uses bellows to help drowning victims: Members of the society recommended the use of bellows to breathe for victims of accidents (mainly drownings).  They recommended that the end of the bellows be placed in one nostril, while the other nostril and mouth were occluded by a second operator. One problem that often occurred was air entering the stomach.  A second problem was the tongue blocking the airway. Goodwin ultimately recommended a catheter be inserted into the other nostril into the esophagus to prevent air from getting into the stomach and to keep the tongue from blocking the airway.  (22, page 2) (18, page 50-52)

1780:  Bag Mask Ventilation:  In this year a reservoir bag was attached to a mask and used to give breaths to infants who were not breathing at birth.  The device was invented by Chaussier.  He also invented a cannula (or catheter) that could be inserted into the airway by blind insertion through the mouth into the larynx.  His reservoir bag could then be inserted to the cannula to provide positive pressure breaths.  (1)  He was likewise the first to provide oxygen breaths to newborns.  (2)

1788:  Endotracheal tube:  The first endotracheal tube was invented in 1788 by Charles Kite (Kyte).  He was a surgeon who wrote an essay titled, "The Recovery of the Apparently Dead," in which he described inserting a tube he referred to as a catheter through one of the nares or the mouth to the lungs whereby the operator could either provide positive pressure breaths either by placing his mouth over a mouthpiece or by using bellows.  To cause expiration Kite recommended pushing in on the abdomen.  Various bellow-type systems were available for providing positive pressure breaths. He also recommended a catheter that was inserted into the esophagus to prevent the tongue from blocking the airway.  On the catheter as a ivory sliding piece that was slid down with a finger into the gullet in order to block the esophagus and prevent air from entering the stomach. Kite's equipment was included in the Case of Resuscitating Instruments that was kept at the various Receiving Houses (Rescue Stations)(1)(23, page 50-52)

1826:  Bellows fall out of favor:  Experiments in 1826 Leroy d'Etiolles performed studies using bellows and noted in a report that "bellows could kill an animal by suddenly inflating the lungs." (23, page 2) This was among the first reports that showed that over inflating the lungs with too much positive pressure could cause the lungs to collapse.  Due to this report, bellows were no longer recommended by the Humane Society.  (23, page 2) However, in 1888, "experiments by Leroy were performed that proved that a collapsed lung only occurred when the pressure forced into the lungs was too high, such as greater than 20-80 mm of mercury in the lungs of infants.  As a result of his experiments, he "invented a safety bellows to obviate these effects.  The bellows had a scale graduated in ages attached to the handles to limit the volume of air delivered." (1)  Experimenters in the succeeding years attempted to create a system of bellows, or methods o fusing them, that were safer to the patient.  

1793:  Intubation to treat diseased patients:  Prior to this time artificial respiration was generally used to treat near drowning patients or for some other purpose.  Yet near the end of the 18th century artificial respiration was thought to benefit people with diseases or conditions that result in dyspnea or asphyxia.  This was a time when a tube was sought to be kept inside the airway long-term as opposed to temporary.  Xavier Bichat, a pupil of French surgeon Desault, describes how Desault decided to insert a catheter into the larynx of a patient in impending respiratory failure as opposed to a tracheotomy. Desault is considered the first to apply artificial respiration for dyspnea.  In many cases the patient's breathing became easier, and in one case the patient's breathing became easier and was extubated 24 hours later. Desaults cather "was a large gum-sized elastic catheter, with two large eyes and an opening inferiorly, adn he introduced it through one of the nasal fossa rather than the mouth."  Catheterization became a common procedure in France, although later fell into disuse.  (3, page 2-4)

1800?:  A paralytic discovered for modern world:   Curare was one of the most famous native American poison, as the Indians often placed it on the tips of their arrows in order to paralyze their prey.  American physicians discovered this poison early on in the 19th century (exact date unknown).  Physicians tried to find a safe dose for using it as a paralytic, which was hard to do.  They also experimented with various diseases to see if it had beneficial effects.  The poison would become an important medicine used by physicians, although it would be a few years before it was proved useful as an anesthetic. (18, page 4, 177-178)

1807:  Method of making Curare discovered:  After Curare was mentioned by Sir Walter Raleigh, many people believed it was made from "poison dart frogs."  Alexander von Humboldt discovered that this was not true, that the poison was derived from various vines in the rain forest.  The stems, roots and leaves were crushed and boiled into a paste, which was sometimes mixed with frog and snake venom.  A thick black paste was placed on the tips of darts.  As they pierced through the skin, the poison would enter the blood stream causing the animal to become paralyzed.  Breathing would cease, and the animal was turned into easy prey.  This would be a major breakthrough for modern medicine, because it would allow physicians an opportunity to experiment with it on animals, and ultimately on patients of various types. (19, page 1674)

1814:  First use of experiments with muscle relaxants:  Benjamin Brodie (1783-1862) and was an English surgeon who performed experiments using Curare (Succicholine) on a donkey, and he proved that so long as the animal was provided with artificial breaths, it could be kept alive during an operation.   (2, page 227)(17, page 25) Charles Waterton gave the Curare while "Brodie supplied the experimental idea." Bellows were used to breathe for the animal for two hours.  The animal lived another 25 years. (17, page 25) 

1839:  Intubation fails  Dieffenbach of Berlin tried to catheterize the larynx of a patient inflicted with croup caused by diphtheria and failed. (8)

Figure 1(23, page 6)

1837:  Artificial breathing condemned:  In 1837 Leroy d'Etoille was concerned about the use of such artificial breathing because he suspected it caused emphysema and would collapse the lungs (pneumothorax). This simply provided another excuse not to perform the procedure, because after the germ theory was established in the late 19th century all methods of performing artificial breaths (positive pressure breathing) was banned for the next 100 years before it's value would be re-established in the later half of the 19th century.  (7)

1845:  Oxygen breaths: A man named Erichson invented the first device that provided positive pressure breaths with oxygen through a cannula inserted through a pipe inserted into one of the nostrils.  He recommended ten breaths a minute.

1850:  Jaw-Thrust technique recommended:  One of the problems that must have ensued when a patient was anaesthetised during surgery was asphyxia (or increased risk of it) due to upper airway obstruction.  To resolve this problem, anaesthesiologist Joseph Clover (1825-1882) performed the "jaw thrust- chin life" procedure."  The physician used chloroform as an anesthetic in over 7,000 operations without a single fatality, so other physicians must have been eager to copy his successful techniques.  Due to side effects, and the death of a little girl as a result, the use of chloroform started to wane by 1864, and by WWI was essentially replaced with better, safer anaesthetics (which included both explosive gases and injection through the hypodermic needle that was invented in 1855 by Alexander wood.) (10, page xxi)(9, page 7)

1855: Intubation fails:  Pediatricians become concerned about the large number of children with diphtheria who die despite emergency tracheotomies.  Reybard in Lyon tried to catheterize the larynx of a patient inflicted with croup caused by diphtheria, and failed.  Weinlechner in Vienna tried to catheterize the laryx of a similar patient, and he too failed.  (8)

(26, page 13)

1858:  Bouchut's Intubation Tube is rejected:  In this year French pediatrician Bouchut became the first to describe insertion of a tube into the airway as opposed to a catheter in a case of dyspnea. The tube he used was a rounded silver tube narrower at the end to be inserted as you can see in Figure 1 (see both figure ones).  It was 1.5 to 2 cm long and 7 cm in diameter. Interestingly, a silk thread was attached to the distal end of the tube that was "brought out to the mouth, and was intended to prevent the tube from going down the trachea or esophagus; and to allow it to be taken out when necessary." He later "insisted on the distinction between his method and catheterism." However, of the seven cases he cited to the French Academy of medicine, only two lived and both required tracheotomy.  

Yet he proved the procedure could be done. Various other physicians described success with this or similar procedures between 1858 and 1880 when the Joseph O'Dwyer introduced his tube.(3, page 5) Some speculate the reason Bouchut's intubation tube (tubage de la glotte), which "set in the glottic space for a few days" was doomed to be rejected due to a bias created by Dr. Armand Trousseau, who was an ardent supporter of the operation of tracheotomy.  Trousseau had previously convinced his fellow physicians that tracheotomy was the best method of creating an airway when suffocation was imminent, even with the low success rate. (12)

The main problem with Bouchut's "small tubes" is that they "did not adapt to the anatomy of the larynx and their sharp edges were a very traumatic cause of lesions to the mucosa and of intense pain."  (12) (also see 26,page 13)  Also of note, since the tube was short, it was barely positioned below the glottis (this would have allowed for air to leak around the tube resulting in diminished lung volumes).  In the end, "Bouchut and his operation were so bitterly criticised that he became discouraged and abandoned it altogether. So effectually was it crushed out that no further investigations were made in this direction for nearly a quarter of a century." (26, page 13)

Richardson's (21)

1867:  Richardson's Double Acting Rubber Bellows:  Benjamin Ward Richardson created a bellow system similar to Hunter's Bellows (although he may not have known of Hunter's Bellows). The original system took up a lot of room, so he invented the double acting bellows, which "consists of two rubber bulbs terminating in common tube that was called the nostril-tube."  One bellow supplied inspiration, the other expiration.  

1869: First intubation during operation:  Performed by Friedrich Trendelenburg (1844-1924) to prevent aspiration of blood and mucus during oral operations.  (13, page 91)

1875:  Blake cures poison victim:  Using a device similar to Richardson's Bellows, Blake connected a reservoir of condensed oxygen to it and treated a case of acute poisoning with success.  Before this time artificial respiration (often referred to as insufflation) was used mainly to treat neonatal asphyxia, but now the focus was also on treating adults.  The nozzle of the device was inserted into the nostril.  1

1878: The first elective intubation: William Macewan was a Scottish surgeon who, on July 5, 1878, performed the first elective intubation on a patient "with a flexible metal tube" who was not anesthetized.  "Once the tube was properly positioned, an assistant provided chloroform-air anesthetic via the tube.  Once anesthetized, the patient soon stopped coughing."  The physician lost confidence in his technique when a tube became dislodged and the patient expired.  His success and failures would become learning points for future surgeons or physicians attempting intubation.  It also should be known that, along with patient anticipation and fear, their was a lot of anxiety among physicians regarding this procedure.  Surely they wanted to help their patients, but they also didn't want to cause further harm by their experimentation.  Macewan, for example, practiced on cadavers prior to intubating any actual living patients.  (9, page 7)

O'Dwyer's Intubation Tube for a child 2-3 years old (23

1880:  The first effective endotracheal tube:  Dr. Joseph O'Dwyer (a pediatrician), and his fellow physicians at the New York Foundling Asylum, observed problems with trachetomy.  Once agian this occurred during an epidemic of diphtheria where too many children were dying due to suffocation from croup. (3, page 9-18)

Tracheotomy was a viable option as an emergency airway, but it was painful and bloody for children, and the end results were not always positive.  He decided another means of breathing for these children was necessary.   (3, page 9-18)

He at first trialed flexible catheters into the nasal passages, yet this didn't meet his satisfaction.  So he devised a tube to be placed into the larynx where it would remain.  In this way, he picked up where Bouchut left off.  By trial and error he tinkered with the device until it met his satisfaction.   (3, page 9-18)

O'Dwyer's set of five Tubes (26, page 19)

The device was made with a bivalve tube with a narrow transverse diameter, and about an inch long."  A shoulder on the upper end prevented the tube from slipping down (perhaps learned from Macewan's error).  By trial and error the tube transformed so the tube was a "plain tube of elliptical form about an inch in length.  (3, page 9-18)

He then played with longer tubes until he found the desired length.  The final tube used was made of brass and lined with gold, and was accepted by the medical community.  (See figures 2 and 3.)   (3, page 9-18)(also see 26, pages 18-21)

A complete set was included in a box, that included sizes for different aged children, an obturator, an introducer, an extractor, and a gag.   The length of the tubes in inches were 1.5, 1 3/4, 2, 2.25 and 2.5. (3, page 9-18)(also see 26, pages 18-21)

The obturator of the physicians choice is connected to the end of the introducer, and this is used to insert the tube.  If necessary a small thread could be inserted and tied to a hole on the outer edge of the tube to prevent it from going down the traches, and to facilitate removal. (3, page 9-18)(also see 26, pages 18-21)

The kit also came with a scale (see figure  5) which helped the physician determined appropriate depth of the tube according to age.  The scale is used like this: "The smallest tube reaches line 1, and is intended for children about one year and under. The next reaches line 2, and is for children between one and two years. The third size, marked 34 on the scale, should be used between two and four years. The fourth, marked 5-7, is for the next three years, and the largest tube is for children from eight to twelve."

O'Dwyer also designed larger tubes and equipment for adult intubation. (3, page 9-18)

1880:  The Fell-O'dwyer Apparatus:  Once O'dwyer intubated his patient's, he needed a mechanism to breathe for them.  This task fell into the hands of George Fell, who invented a t-piece.  One end of the t-piece was connected to the tracheal tube, and the other to bellows.  The bellows were used to provide positive pressure breaths.  Of course the problem here is it took a lot of manual labor to provide breaths for such patients.  Still, the technique provided physicians an opportunity to help their patients, both when a physician needed to create an emergency airway, and when surgeons needed to perform more invasive operations.  (9, page 7) 

O'Dwyer's introducer connected to obturator (23, page 16)

1887-1888:  George Fell's Apparatus (Hand Operated Bellows): In 1887 Dr. George Fell invented a system of bellows whereby the operator would use his hands to provide positive pressure breaths.  He connected the bellows to either a tracheotomy or face mask. He became the first to perform this procedure on a human in a case of poisoning. (6, page 283)  (22, page 3) In order to connect the apparatus to the airway, Fell invented a t-piece.  One end of the t-piece was connected to a tracheal tube or mask, and the other to the bellows.  (9, page 7)

Figure 5

1889: The first rubber endotrachal tube:  Thomas Annandale devised a tube made of Indian rubber that was connected from the tracheostomy to (a cap is attached to the trach for just this purpose) to a small tumbler filled with "a piece of absorbent wool at the bottom, upon which chloroform or ether is from time to time sprinkled."  This was significant because a similar material would be used by a later physician to create an endotracheal tube that would be commonly used for over 40 years. (27, pages 261, 838)

1891: The Fell-O'Dwyer Apparatus (Foot operated Bellows)  Once O'dwyer intubated his patient's, he needed a mechanism to breathe for them.  George Fell's apparatus must have worked, yet it needed to be fine tuned for ease of use.  He revised Fell's system so that breaths were provided by pressing down on a lever with his foot.  O'Dwyer preferred to connect his bellow system to an endotracheal tube.  O'Dwyer was concerned about over-distention of the lungs due not allowing enough time for expiration, and therefore recommended giving slow breaths, or 10-12 per minute. (6, page 283)

1891:  Concerns of Intubation:  By the late 19th century many of the same concerns physicians have today about intubation were considered.  One such concern being the ulceration of tissue due to pressure of the tube set upon it for a long period of time.  Tubes were generally taken out after six days with success, although in some cases were left in 12 days or longer. Dr. Rank, a German physician, ultimately recommended removal of the tube after 10 days, and if necessary, the physician should consider tracheotomy. Some physicians recommended extubation after the 5th day, which would be in line with modern protocols.  Feeding the patient was also a concern, and was either done with soft foods or liquids, or by nasalgastric tube.  It was recommended that if the tube was accidentally spit up that the nurse take advantage of the moment to try feeding the patient prior to re-introducing the tube (if the tube is still needed). (3, page 29-20)

O'Dwyer intubation kit as advertised to physicians in 1901.  (16, page 228)

1892: Dr. O'Dwyer makes pitch for intubation:  In 1892, and according to the New York Academy of Medicine,  Dr. O'Dwyer gave a presentation where he explained that poor statistics shouldn't discourage physicians from performing the procedure, as most studies are performed by "hospital staff, who did not remain on duty long enough to obtain the skill necessary to perform intubation successfully." (14, page 557)

He said:

"The operation of intubation is a difficult one, because it must be done very rapidly.  A period of ten seconds is not safe in some cases, and fifteen seconds would certainly produce apnea in many instances.  The necessary touch and skill require much practice, and this should be acquired on the cadaver until the tube can be inserted in different subjects in about five seconds. It is much easier to perform intubation in some subjects than it is in others.  After such prolonged practice, the operation may be done with comparative safety... No great amount of surgical skill is required to perform tracheotomy, but good nursing is a necessity.  Intubation, therefore, calls for a trained operator, and tracheotomy for a trained nurse."(14, page 557)

Here is another picture of O'Dwyer's Intubation kit. (26, page 27)

He noted that regardless of the challenges, "intubation has supplanted tracheotomy to a very considerable extent, especially in this country (the U.S.)."  O'Dwyer further noted that with his new improved equipment, he never finds a case in which he finds it impossible to insert the tube. (14, page 557)

1892:  Dr. Gay makes pitch for intubation:  Another physician, Dr. George S. Gay of Boston, said that "intubation is by no means perfect, but it possesses sufficient advantages to give it a permanent place in the treatmenet of acute laryngeal stenosis (narrowed upper airway caused by croup secondary to diphtheria).  Although it will never entirely displace tracheotomy, the former has some important advantages over the latter.  No anesthetic is required; there is no hemorrhage.  Unless one's early experience with intubation has been particularly favorable, he is likely to prefer tracheotomy.  The strongest advocates of intubation will be found among those who have had the largest experience with it.  The consent of the parents to perform intubation is more easily obtained, and the operation can be resorted to earlier." (14, page 557-558)

This shows the proper position of operator and assistant. 

The assistant holds the head "securely and slightly backward."

The gag should be introduced in the left angle of the mouth,

 well back between the teeth, and widely opened. The operator

 should then quickly seize the introducing instrument with the

 tube attached, hook the loop over the little finger of the left hand,

 and introduce the index finger of the same hand, closely followed

 by the tube" The tube should sit in the larynx. (26, pages 38-40)

1892: Dr. Jacobi makes pitch for intubation:  According to the Medical News, Dr. Abraham Jacobi said he performed many tracheotomies (between 600 and 700), but around 1887 he listened to a discussion at the New York Academy of Medicine in which he was "converted from trachheotomy to intubation."  He warned that, as noted by the Medical News,  "It is very easy to get the parents consent to perform intubation, but it is very difficult to get their consent to perform tracheotomy.  For this reason in many cases the latter operation is performed to late."  He notes that despite improvements in aeseptic techniques, it's still impossible to prevent dying due to sepsis infection of the blood). The Medical News also mentions that "Dr. Jacobi said that, although he is in favor of intubation, adn always recommends it, he has never performed the operation personally.  Thirty years ago he was a professed tracheotomist, and on one occasion he was told that he was a good enough man, but that he cut too many throats." (14, page 558)

1893: Cuffed Endotracheal Tube:  It must have also been discovered early on that air was leaking around the tubes, instead of inflating the lungs.  Likewise, some patients must have vomited when the tube was inserted past the gag reflex, and this would have caused aspiration pneumonia, which would spell doom for most patients back then.  Physicians must have sought some means of securing the airway around the tube. According to the 55th anniversary publication of the German Society of Anaesthesiology and Intensive care, Victor Eisenmenger became the first to use an endotracheal tube that had a cuff on the distal end of the tube that was connected by a pilot line to a pilot balloon.  Air was inserted with a syringe into the pilot line, and both cuffs would become inflated.  The physician would know the distal cuff was inflated when the pilot cuff was inflated. Such a system was soon adapted by other physicians.  (13, page 91)

This is a picture representing insertion of O'Dwyer's tube.
The dotted lines represent the outline of the operator's forefinger.
Yes, back then a finger was used to assist the endotracheal tube to
the desired location in the airway.  The proper tube should be
selected, attached to the introducer, and then introduced to the airwa.
 It was inserted under the tip of the epiglottis, and into the larynx
You  knew the tube entered the larynx when the patient coughs and
the breathing becomes easier.  If it enters the esophagus, breathing
will not become easier.  Once the tube is inside the larynx, the
tube should be disconnected from the introduces.  The tube
should then be pressed forward until it is positioned in the pharynx
Physicians were further warned that "no force should be used,
no anesthetic is required, and the operator should not require
longer than five to ten seconds.
The risk, as you might imagine, was getting bitten by the patient,
and inhaling the same air as the patient, and then getting
the same disease.  Some physicians sacrificed
their lives by attempting to save the lives of their
patients by this procedure.  (26, page 40-42)

1895: First use of laryngoscope:  A laryngoscope was invented to visualize he back of the airway, and was first used by Kirsetein in Germany (15, page 372)

1896: The Fell-O'Dwyer Apparatus modified:  Dr. Northrup recommended the Fell-O'Dwyer apparatus, and it was later modified by Tuller and Hallion of France, and later by Doyan.  Doyan's "apparatus consisted of 'duplex' bellows (for insuflation and suction) attached to an intralaryngeal cannula. (22, page 3)

1900:  Cuffed Endotracheal Tubes and laryngoscopes:  Around the turn of the century cuffed endotracheal tubes (ETT) were used with increased frequency.  A larygoscope was first described in 1855 using sunlight to see the vocal cords, and by 1913 a battery powered laryngoscope with an external light was invented.  This was refined so it had a handle with a battery and a light bulb at the end of the scope for easy visualization of the vocal cords.   (2)

1900: Oral intubation becomes popular: Initially the procedure of oral intubation must have been as nerve wracking to the physician as the patient and the patient's family.  However, as with anything, the more it was performed the more confident and competent the physician became in both recommending and performing the procedure.  According to a 1911 edition of the New York Medical Journal there must have been enough successes with the intubation by the mouth (per os) by 1900 that it had "found many followers."  (12, page 760)


1900:  Indications for intubation:  As more and more physicians became comfortable with laryngeal intubation, they began experimenting with the procedure both on cadavers and on real live patients.  The ultimate goal, of course, was to help patients survive diseases that otherwise would have taken their lives.  By 1911 some of the indications are mentioned in the New York Medical Journal: (12, page 760)

• Narcosis
• Operations (of the mouth, nose, throat and thorax) (12, page 760)

1900-1912:  Intubation technique improved: Frank Kuhn, a German physician, published a series of papers where he "described the techniques of oral and nasal intubation that he performed with flexible metal tubes composed of coiled tubing similar to those now used for the spout of metal gasoline cans."  (11, page 7)  

The tubes were of his own design. (13, page 91) As a local anaesthetic to prevent the gag reflex he used cocaine.  He introduced the tube into the airway with a metal stylet.  He used his the index finger of his left hand to lift the tongue and the glottic tissue, and used his right hand to insert the tube through the vocal cords.  While cuffs were used by other physicians to seal the airway, he preferred to have it sealed by "positioning a supralaryngeal flange near the tube's tip before packing the pharynx with gauze."  (11, page 7)  (13, page 91)(also see 22, page 3) 

To see a very good picture of Kuhn's procedure check out this link.  

1902: O'Dwyer apparatus modified again:  This modification was made by R. Matas who 'Constructed an apparatus in which a modified O'Dwyer tube was connected with an automatically acting pump.  The pump contained originally two independent metal cylinders for inspiration and aspiration.  However, the first experiment made on a dog convinced Matas that the suction force, exercised by the aspiration cylinder, does damage to the lungs, and he eliminated that part of the apparatus. (22, page 3)

1913:  Modern laryngoscope invented:  A better laryngoscope as invented by Jackson, and it was later improved by Miller and Mackintosh (see below) (14, page 372)

1914-1918: Magil invents blind intubation:  During WWI Dr. Magill performed a variety of facial reconstruction surgeries. He discovered that in order to do such surgeries the patient had to be intubated.  Along with Stanley Rowbotham, he developed a method of tracheal intubation.  He blindly inserted one tube of gum elastic design into one nostril.  In this way he coined the term "blind intubation."  (24, pages 8, 753)

There were two problems with this system.  One was that anesthetic gas was escaping the tube, and the operating physician was inhaling this gas. Obviously, this affected his work.   The other was that blod and other debree from the operation would fall into the airway when the tube was pulled.  Obviously, this was detrimental to the patient.  So a two-tube system was developed.  One tube was blindly inserted into a nostril into the larynx to breathe and to apply the anesthetic, and the other through the mouth into the pharynx to provide for the escape of gases.     (24, pages 8, 753)

He became so proficient at his method that students from all over came to watch and learn his method.  While he taught his method, other physicians continued to have trouble inserting the tubes due to patient agitation, while Magill did not.  Magill had a secret that he refused to tell the students: that he used cocaine as a local anesthetic to the throat.  (25, page 110) 

The rubber endotracheal tubes used by Magill were standard for the next 40 years until being replaced with plastic tubes. (24, page 8)

1920: Magill Forceps introduced:   In order to guide the nasal tube into the airway, Magill used forceps that still bear his name (Magill Forceps) (15, page 372)(24, page 8)

1926: Guedel experiments with cuffed endotracheal tubes:  Noting the need to protect the lower airway from secretions and surgical debris, Arthur Guedel (1883-1956) performed experiments with using a cuffed endotracheal tube.  His cuff was made out of rubber. His experiments also determined that the best place to position and inflate the cuff was just below the vocal cords.  This, he found, was the best way of protecting the airway during intubation.  One this task was accomplished, he aimed to encourage stubborn American physicians that intubation of the benefits of intubation.  (24, page 8)

1926: Guedel inspires American physicians to intubate:  While European physicians intubated on a regular basis during operations, American surgeons used other means.  Noting the benefits of intubation, Arthur Guedel put on a show where he went around the country with his dog named Airway.  He would anesthetize and intubate his dog, and then submerge it under water.  Just as the audience suspected the dog was dead, he would pull it from the water, extubate it, and the dog would shake off the water and run off.  These shows became known as the Dunking Dog Shows proved that intubation not only allowed the physician to breathe for the dog, but the inflated cuff prevented water from getting into the dogs lungs.  These efforts worked, as American physicians soon became proficient in intubation. (25, page 111)

1930:  Oral Airway Introduced:  Ralph Waters (1883-1979) introduced the flattened oral airway, and it was later modified by Guedel by fitting the oral airway with a "rubber envelope in an attempt to reduce mucosal trauma." (24, page 753)

1932:  One lung intubation introduced:  Ralph Waters accidentally allowed an endotracheal tube to slip all the way into a patient's lungs, and he inflated the cuff.  In this way he learned that one lung could be intubated with a long endotracheal tube while the other was operated on.  This made it possible to do lung operations.  (24, page 8)(25, page 111)

1942:  Anesthesia during intubation: By the 1880s intubation was being increasingly used for children with airway stenosis secondary to croup secondary to diphtheria.  As a physician observed that the patient was going to suffocate to death unless he did something, the choice was offered to the parents: intubation or tracheotomy?  (2, page 227) (19, page 1674)

Intubation must have presented as the best option in many cases, as the procedure would avoid a cut of the throat.  A problem that continued was the procedure caused quite a bit of anxiety on the part of the patient, as you might imagine.  If the child fought the efforts of the physician, this could make the procedure very difficult to perform. (2, page 227) (19, page 1674)

Cocaine was occasionally used as a local anesthetic to prevent the gag reflex, and general anesthetics were occasionally used to paralyze the patient, although these were only used if the physician was familiar with them and comfortable with their use.  (2, page 227) (19, page 1674)

 In 1942, Harold Griffith, A Canadian anesthesiologist, made a major breakthrough in this regard on January 23, 1942, when he and his assistant, Dr. Enid Johnson (also an anesthesiologist) used Curare to paralyze a patient prior to intubation.  He used it as an anesthetic in 23 operations, and wrote a report on his successes with it.  (2, page 227) (19, page 1674)

This was a major breakthrough because it allowed the surgeons to sedate and ventilate patients during the operation.  (2, page 227) (19, page 1674)

WWII:  Intubations proficiency increases worldwide:  In preparation for the traumas generally associated with battle wounds, anesthesiologists practiced and became very proficient at performing the procedure of intubation.  The methods learned became standard practice, and oaver time intubation training became a regular part of a physician's training.  (25, page 753)

1964: Plastic endotracheal tubes introduced: They were actually made of polyvinylchloride (PVC) with an inflatable cuff. Rubber tubes tend to harden when exposed to body temperature.  PVC tends to soften at body temperature, and is therefore less likely cause damage to tissues of the airway.  The tubes are also clear and opaque.  They come with markers so caregivers know how far down the tube is inserted.

1970:  High volume, low pressure cuffs introduced:  Previously, cuffs were low volume high pressure.  When inflated, these cuffs came into contact with very little area of the trachea, and created a great seal.  However, due to the high pressure, risk of cutting off circulation and causing necrosis was high.  High volume, low pressure cuffs would come into contact with more tracheal tissue, although the lower pressure was less traumatic.  Surely the cuff pressure would have to be minimized, and the cuff may need to be rotated up or down 1-2 cm on a regular basis to minimize tissue damage, yet this was a much better set up than the older cuffs. The drawback is the seal is not ideal.

Conclusion:  So you can see that physicians were slow to begin using intubation, although experiments by the few, in an attempt to help their patients, resulted in both an improvement in the technique used and the equipment available.  By the 1940s intubatoin during surgery would become standard, and by the 1950s the procedure became standard in across the medical spectrum, including at on the scene of an accident and emergency rooms.

Likewise, while fireside bellows remained the preferred method of providing breaths through the endotracheal tube, the quest was ongoing to find a mechanical device that would provide breaths in a means that was less laborious for the provider, and safer for the patient.

References:

1. Price, J.L., "The Evolution of Breathing Machines," Medical History, 1962, January, 6(1), pages 67-72; Price references The Bible, Kings, 4: 34 
2. Szmuk, Peter, eet al, "A brief history of tracheostomy and tracheal intubation, from the Bronze Age to the Space Age," Intensive Care Medicine, 2008, 34, pages 222-228
3. Ball, James B, "Intubation of the Larynx," 1891, London, H.K. Lewis
4. Woollam, C.H.M., "The development of apparatus for intermittent positive pressure respiration," Anaesthesia, 1976, volume 31, pages 537-147
5. Previtera, Joseph, "Negative Pressure Ventilation: Operating Procedure (Iron Lung)," Tufts Medical Center, Respirator Care Programs, http://160.109.101.132/respcare/npv.htm, and http://160.109.101.132/respcare/ironlung.htm, accessed February 27, 2012
6. Tissler, Paul Louis Alexandre, "Pneumotherapy: Including Aerotherapy and inhalation...," 1903, Philadelphia, Blakiston's sons and Company, page 284,5
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9. Barash, Paul G,  Bruce F. Cullen, Robert K. Stoelting, Michael Cahalan, M. Christine Stock, editors, "Clinical Anesthesia," 6th edition, 2009, China, Lippincot Williams and Wilkins
10. Subramaniam, Rajeshwari, "A primer of anesthesia," 2008, MO, Jaypee Brothers Medical Publishers
11. Barash, Paul G., Bruce F. Cullen, robert K. Stoelting, Michael k. Cahalan, M. Christine Stock, "Clinical Anaesthesia," 6th edition, 2009, Philadelphia, Lippincott
12. Foster, Frank P., editor, "Book Notices," New York Medical Journal, volume 94, New York, A.R. Elliott Publishing Co. 
13. Schuttler, Jürgen, editor, "55 years: German Society of Anaesthesiology and Intensive Care Medicine," 2012, Germany, Springer
14. Gould, George M., editor, "Society Proceedings: New York Academy of Medicine: Stated Meeting, Thursday Evening, October 20, 1892," The Medical News, A Weekly Medical Journal," July-December, 1892, Vlolume LXI, Philadelphia, Lea Brothers and Co., pages 557-558
15. Hagberg, Carin A., "Benumof's Airway Management," 2007, Philadelphia, Mosby
16. "Blees-Moore Instrument Company: surgical instraments," 1901, St. Louis, MO, Burton and Skinner Print
17. Miller, Ronald D., editor, "Miller's Anesthesia," 7th edition, volume 1, 2010, Philadelphia, Churchill Livingstone Elsevier
18. Vogel, Virgil J., "American Indian Medicine," 1970, London, Oklahoma University Press
19. Wheeler, Derek S., Hector R. Wong, Thomas P. Shanley, editors, "Pediatric Critical Care Medicine: Basic Science and Clinical Evidence," 2007, London, Springer
20. "Drowning: Historical-Statistical Methods of Resuscitation," no author nor editor listed, Published by Lungmotor Company, Boston, Massachusetts, 1920
21. Hughes, Martin, Roland Black, "Advanced Respiratory Critical Care,"  2011, New York, Oxford University Press; material from section 3.1: "Invasive Ventilation Basics: Development of Invasive Ventilation (history)."
22. Meltzer, S. J., "History and analysis of the methods of resuscitation," Medical Record: A Weekly Journal of Medicine and Surgery, July 7, 1917, Volume 92, Number 1, New York, 
23. The Forty Ninth Annual Report of the Royal Humane Society, For the Recovery of  Persons Apparently Drowned or Dead," 1823, London, 
24. Barash, Paul G. Bruce F. Cullen, Rober, "Clinical Anesthesia," 2009, Philadelphia, Lippincott
25. Friedman, Meyer, Gerald W. Friedman, "Medicine's 10 Greatest Discoveries," 1998, Yale University
26. Waxham, F.E., "Intubation of the Larynx," 1888, Chicago, published by Charles Traux (Waxham was an early proponent of intubation for diptheria and croup. 
27. Gould, George M, "American Year-book of Medicine and Surgery," 1899, Philadelphia, W.B. Saunders
28. Curry, James, "Observations on Apparent Death from drowning, hanging, suffocation by noxious vapours, fainting-fits, intoxication, lightning, exposure to cold, & etc., and an account of the means to be employed for recovery. To which are added the treatment proper in cases of poison, with caution and suggestions respecting various circumstances of sudden danger," 2nd edition, 1815, London (the 1st edition was published in 1792)