Friday, March 09, 2012

1950- 1980: The evolution of the artificial respiration

The technique of inserting a hollow tube through the oral cavity to the lungs was first attempted as far back as 1788, and by 1858 the equipment and procedure was improved enough for intubation to be recommended to the medical community.  The idea, however, was rejected as preposterous by all but a few physicians who dreamed that the method might some day provide a viable airway, if not given up on.

A few random physicians attempted the procedure in order to save a life, or to perform some difficult operation, yet successes were far and few between.  Yet thanks to those who dreamed of helping their fellow human beings, and who never gave up despite past failures, the procedure was slowly

By the turn of the 20th century the medical community was becoming increasingly confident in recommending and performing the procedure of intubation.  We have to realize that initially the medical community rejected the procedure altogether

1940:  Miller 

1942:  Anesthesia during intubation:  Endotracheal tubes were refined during the 19th century so by the turn of the century a variety of tubes were used, including metal and rubber tubes. Occasionally anesthetics were used to paralyze the patient prior to inserting such a tube, yet this wasn't common practice until 1942 when Harold Griffith, a Canadian anesthesiologis, used curare (succicholine).  This was a major breakthrough because it allowed surgeons the opportunity to sedate and ventilate patients during operations.  (1, page 227)

 It was also during this decade that Robert Miller refined the laryngoscope so it was straight, and it's referred to as either the Miller or straight blade.  Roger MacIntosh refined the laryngoscope so it was curved, and it's reverred to as either the MacIntosh or curved blade.  Variations of both are still used to this day, and both come with a handle with a battery that the blades attach to.  At the end of the blades are a small lightbulb so the person intubating can visualize the vocal cords.  During WWI Sir Ivan Whiteside Magill was the first to use rubber endotracheal tubes which he inserted through the nose and assisted their transfer into the airway with forceps we now refer to as Magill forceps.  In this way he also dubbed the term "blind intubation." (2)  Magill was said to have "mastered the technique of

  1. Szmuk, et 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, reference to page 227
  2. Subramaniam, Rajeshwari, "A primer of anesthesia," 2008, MO, Jaypee Brothers Medical Publishers

1947:  Morch's Piston Ventilator:  Dr. Ernst Tier Morch designed one of the first ventilators that provided positive pressure breaths to a patient.  It became one of the first such ventilators available in the United States and Europe.  It allowed for inhaled air to both be humidified and oxygenated, and provided an alternative respirator to the iron lung in ventilating polio victims.  It was also used during abdominal surgeries.  A second and third model would be introduced during the 1950s. (3)  It was the first modern type volume ventilator on the market. (4)  One major disadvantage is that it only allowed for controlled ventilation, which made it very difficult to ventilate patients who were awake and alert and orientated because it would be very uncomfortable.  Bucking of the vent would be quite common.  Another problem is alarms were limited. 

1948:  Continuous Positive Airway Pressure:  During WWII Alvin Barach supervised experiments whereby Continuous Positive Airway Pressure (CPAP) was used on a variety of pilots who traveled to high altitudes.  After the war he studied the use of CPAP on a variety of patients, although his work was relatively ignored until the 1980s when studies would confirm CPAP was beneficial for COPF and sleep apnea patients.  CPAP would also be studied in the 1980s as a means of preventing a patient from requiring intubation.  (v5)

1948:  Monaghan Ventalung Respirator:  It was the first machine that could be used as a ventilator and provide intermittent positive pressure breathing (IPPB).  According to Dennis W. Glover in his book, "The History of Respiratory Therapy:  Discovery and Evolution," these machines were used during WWII as ventilators.  It was also during this time IPPB therapy was first used.  The machines were introduced to hospitals in 1948.  At this time positive pressure breathing either by Ambubag or machine were provided by inserting a cuffed tracheotomy tube into the patient's airway.  A rubber mask could also be used.  Cuffed rubber ETTs were also available if necessary.

1950s-1970s:  Rubber masks:  Positive pressure breaths were often provided by using a rubber mask over the patient's mouth and nose.  One of the major complications of the rubber masks used at this time was that they were opaque and concealed aspiration or foaming pulmonary edema, and this was noted as a major disadvantage of such masks.  Another disadvantage was prolonged use caused facial skin breakdown.   Another disadvantage is air would often leak around the masks.   And yet another complication was the masks required a person to hold the mask securely on the patient's face.    When done over a prolonged period of time this could become very tiresome.  When used on polio patients nursing assistants or respiratory therapists would often work in two hour shifts.  The disadvantages of these masks could be compensated for by tracheotomies and inserting a catheter, and later  by intubation.  (v6)

1952: The Bird Mark I:  Roger Manley was an anesthesiologist who was initially concerned with ventilating patients given anesthetics.  It could be used as a ventilator and to provide IPPB.  It was often referred referred to as the Manley Ventilator.  He later refined it and re-branded it as the Mark II.

1952:  Bennett Pressure Breathing Unit:  It was studied successfuly in 1948 and marketed as the main alternative to the Bird Mark 1 by creator V. Ray Bennett.  Like the Mark I and Mark II it was a  pressure cycled ventilator.  It had a nebulizer cut for the nebulizatiion of Isuprel (a bronchodilator) and Alevaire (mucus thinner), Mucomyst (mucolytic) and ethyl alcohol (to cut allay the bubbles in foaming pulmonary edema).  The machines was commonly used as a ventilator instead of iron lungs when suctioning of the airway was required.  Iron Lungs and IPPBs being used as ventilators were pretty much phased out when volume ventilators were proven to be more effective and safer ventilators.  Bennet later refined this machine and re-branded it as the Bennett PR 1 and Bennet PR 2, both of which were still mentioned in respiratory therapy texts through the 1990 as you can see here.  (t7)

1951:  Engstrom ventilator:  Carl-Gunnar Engstrom invented a respirator that would allow "efficient control of gas volume delivered to the patient and also allows for active exhalation.  It can also be used for both adults and children, and it is the first apparatus suitable for long-term ventilation as well as for use during anesthesia."  Engstrom wrote a paper suggesting how inadequate iron lungs were and how much better volume ventilators were for long term ventilation of patients. (8)  Like the Morch Ventilator, it was among the first volume ventilators.  However, also like the Morch Ventilator, alarms were limited and the only mode was was controlled ventilation. 

1953:  AMBU Bags

While not a machine, per se, the bag valve mask (BVM) is a significant development in providing artificial breaths to patients in need. The AMBUbag invented in this year provided another less expensive option to expensive iron lungs and the recently invented and very complicated pressure respirators.  This became an important option for ventilating polio victims who presented with excessive and/or thick secretions.  BMVs were could be connected to a rubber mask for temporary ventilation, or to a tracheostomy for long-term ventilation.  Therapists worked in two hour shifts giving breaths.  You can read more about the history and significance of BVMs by clicking here
1955: Bird Universal Medical Respirator ( Bird Mark 7 Universal Respirator , the Bird)

Dr. Forrest Bird became interested in creating a device during WWII that would allow pilots to fly higher.  This quest lead to the first  pneumatic respirator, meaning it was completely driven by compressed air and no electricity was required.  It was a small, portable green box, and all you had to do to start it up was plug it into a 50 PSA oxygen source, such as an oxygen tank or piped in oxygen system, and turn up the flow.  Like the Mark I and Bennett respirators it was pressure cycled.  It was portable and provided a nice, easy means of providing mechanical breaths. For this reason the Mark 7 became the most popular such IPPB machine, although the  Mark 1,  Bennet TV-2P Vivian, Monaghan Ventalung Respirator, and the Manley Ventilator provided viable alternatives.

These machines had another use that ultimately became the embarrassment to the profession.  You can read more about that by clicking here.

1960:  Amsterdam Infant Ventilator Mark I:  It was one of the first ventilators available to provide IPPB to infants with respiratory distress.  In 1974 the benefits of CPAP were noted, and a screw clamp was inserted on the expiratory limb of the circuit so the device could provide both IPPB and CPAP.  It was used both in neonatal intensive care units (NICU) and operating rooms.  Calculators were used to determine tidal volume, minute ventilation, and total flow.  (QQ14)  It's generally referred to as a constant flow ventilator with a pneumatic time cycler.  The ventilator was updated as the Mark II.

1964:  Emerson Volume Ventilator:  According to Richard Branson in his 1998 article in Respiratory Care celebrating the life of John Emerson, Emerson was the second to produce a volume ventilator.  Bronson described it like this:
"This simple devise resembled a green washing machine and used a piston to deliver precise volumes. Oxygen was added into a ‘trombone-shaped’ accumulator connected to the intakeof the piston for delivery of elevated FIO2. The tidal volume was changed by a crank on the front of the machine, which controlled the stroke of the piston. Respiratory rate and inspiratory-to-expiratory-time ratio (I:E) were adjustable. The humidifier was a modified pressure cooker and was known as the Emerson Hot Pot. A belt, connected to a DC motor and pulley wheel, served to move the piston. In case of failure of the existing belt, a spare was hung inside each cabinet. The belts were similar to those used to circulate air in forced air gas furnaces in homes. On numerous occasions I have heard the story of the belt becoming loose or breaking and the spare found to be missing. Under these circumstances, the resourceful respiratory therapist would run to the parking lot and obtain the belt from a Volkswagen Beetle (the old one) and place it in the Emerson to restore it to working order. I’ve never looked to see whether the two belt sizes are compatible because it’s such a good story. In any event, the Emerson Postop VolumeVentilator was reliable and would allow ventilation of patients when other devices failed. Emerson’s device was not the first of the piston ventilators (M¨orch and Engstrom preceded him), but it was the first device to allow independent control of I:E." (15z)
1964:  Bourn's Piston Driven Infant Ventilator (LS104-150)

This was the first ventilator specifically made for infants.  It was a volume ventilator, which meant that while it may have save lives, it also may have been responsible for forcing too much air into little lungs and causing collapsed lungs which further hampered physician's attempts to save sick neonates.  IMV ventilators and CPAP were later proven to be more effective and safer for use on neonates.

1967:  The Puritan Bennett MA1

In 1940 Ray Bennet produced a gas delivery system that involved a "jewled pneumatic valve - the 'valve that breathes with the patient."  It was this concept that allowed the Puritan Bennett company to create the the MA1. (a16) (b17)

The ventilator gave care practitioners much more control over the patient's breathing.  One reason is  the machine offered more than one mode instead of just control.  Along with control modes it offered assist control (AC), which allowed the patient to trigger spontaneous mechanical breaths between scheduled machine breaths.  Later on Intermittent Mandatory Ventilation (IMV) was added via an external line,  and later Synchronized Intermittent Mandatory Ventilations (SIMV).  IMV and SIMV allowed the patient to take spontaneous breaths between machine breaths and made it much more comfortable for the patient.

It was a compact and durable unit that could easily be carted to the patient's bedside, and provided the patient with positive pressure breaths once connected to an endotracheal tube (ETT) that had to be inserted into the patient's airway.  This device and others like it (volume ventilators) took over for the above mentioned IPPB machines as the main sources for mechanical breathing.  Because the patient was intubated, gaining access to the patient was much easier for nurses and doctors, and airway maintenance was much more efficient.  For it's time, the MA1 was a very good and durable ventilator.

The basic settings were simply dialed into the machine: rate, tidal volume, sigh depth, sigh rate, etc.
While it was a bit complicated, the ventilator could be connected with many different alarms and manomoters, such as high rate, low rate, high pressure, low pressure, and tidal volume and rate.  However, these could be quite complex to set up and operate.

Many hospitals had one.  In fact, when I started as an in 1995 the hospital I worked for had one as the "emergency back up" ventilator.  All the knobs were on the front and it was pretty easy to set up, it was just a challenge to operate all the alarms.  Thankfully the device was shipped to somewhere in Asia prior to the turn of the century.  Ultimately there was an MA2, yet it wasn't anything as popular as the old faithful MA1.

1967:  PEEP:  Ashbaugh and Petty were the fist to describe a condition called Acute Respiratory Distress Syndrome (ARDS), and they described it as a severe respiratory distress associated with refractory hypoxemia, or hypoxemia (low oxygen in the blood) that does not get better with increased oxygen, and decreased lung compliance and diffuse lung infiltrates.  The disease condition causing the syndrome may vary from patient to patient, including sepsis, pneumonia, trauma, etc.  In 1971 the condition was renamed adult respiratory distress syndrome to differentiate it with the neonatal form.  It's often referred to as noncardiogenic pulmonary edema.  There was a high rate of morbidity (as high as 100 percent) with the syndrome, and the initial treatment they found effective and eventually recommended was increasing Positive End Inspiratory Pressure (PEEP).  A valve was inserted at the end of the expiratory circuit.  Since this time various treatments have been recommended, such as low tital volumes (6-10cc/kg/ideal body weight) with positive results. (yyyyyyy)

1970:  Respirator name change

I'm probably no alone in wondering why sometimes these machines are referred to as respirators and now they seem to be more commonly called ventilators.  The actual reason may continue to elude us. However, Glover describes in his great book on the history of respiratory therapy that sometime around 1970 the term respirator was changed to ventilator.  As a rule of thumb, I think we can safely conclude that most breathing machines made prior to 1970 were referred to as respirators, and most breathing machines made after 1970 are referred to as ventilators.  Perhaps only the Lord knows why the change in name was made, or even if it was an official name change.

1969:  Baby Bird

By the 1960s there were a series of ventilators that provided breaths for adults, yet few that would do the same for infants.  A major concern was that providing pressure into an infant's lungs would cause a pneumothorax.  Up to this point the main method of ventilating newborns was with neonatal Ambu-bags, although there were occurrences where a gentle squeeze of the bag may turn to a harsh squeeze and a collapsed lung.  So the market was open for a baby ventilator to deliver consistent breaths.  Forrest Bird tapped into this market with the first ventilator specifically designed for ventilating infants.  It was time cycled and pressure limited, and provided constant breaths at a desired frequency.  It was crude by today's standards, and required some math to set up and maintain, yet it was a good ventilator for its day.  This and other similar ventilators helped to significantly reduce infant mortality rates by up to 70 percent by the end of the decade

1971:  Servo 900 Ventilator

It was small, slightly larger than two shoe boxes, and all the knobs were on the front.  It became known as a minute ventilation ventilator because the respiratory therapist would set the minute ventilation and the tidal volume and respiratory rate would be secondary.  In this way, in volume control mode the tidal volume could be set.  This machine had a sensor to make sure the tidal volume was adjusted with changes in patient compliance so the patient was guaranteed to get the set tidal volume.  This was the first ventilator to have this function.

In order to set tidal volume, though, you had to do a little math.  I know because when I did my clinical rotation in 1996 at Blodgett Hospital in Grand Rapids Michigan they still used this ventilator on a regular basis.  It was also commonly used on cardiac patients at Mott's Children's Hospital at the University of Michigan when I did a rotation there.  Many students were afraid to use it, yet once you were used to it it was a very nice ventilator.  However, students were thankful when it was ultimately replaced by the Servo 300 Ventilator.

It was the first ventilator to have all the alarms you needed right on the machine, and it was also the first ventilator to allow for the addition of a device so you could see pressure and flow curves.  This was nice because you could see what you were doing and make changes based on the needs of the patient. (d18)

 It was also the first ventilator to provide both volume control and intermittent positive ventilation (IMV), which was later improved to synchronized intermittent positive ventilation.  These new modes improved the physician's ability to wean a patient from the ventilator. (e19)

The ability to measure exhaled CO2 was a feature added in 1978, which provided clinicians a noninvasive means of measuring CO2 other than by obtaining an invasive arterial blood gas (ABG). The inline CO2 monitoring was nice because it allowed clinicians to quickly adjust to changes in the patient's condition rather than wait up to 30 minutes for the results of an ABG to be returned.  (e20)

In 1981 Positive End Airway Pressure was introduced to the Servo 900 series.  There were other methods of adding PEEP prior to electronic PEEP, yet they were much more complicated and provided non-measurable and unstable levels with increased expiratory resistance.

Eventually pressure support (PS) added, making the Servo 900 C the first ventilator that interacted with the patient and supported his breaths. Before PS was an option all modes of ventilation provided mandatory breaths.  Pressure control was also added to the Sero 900 C.  (e21)

1973:  Intermittent Mandatory Ventilation:  (22xxxxx)  The concept that a patient be able to take a spontaneous breath between mechanical breaths only made sense.  It was believed if this was possible it would prevent the patient from bucking the ventilator, giving the patient more control.  Other initial claims were that it would reduce the need for sedation, improve kidney and heart function by lowering intrathoracic pressure, facilitate weaning from the ventilator.  Initially the IMV set up was complex and required intensive effort by the patient.  With this new mode, engineers concentrated on finding better methods of allowing the patient trigger breaths.

1976:  Bourne BP 200 respirator

It was another in a line of neonatal ventilators.  Like the Baby Bird, it was set up using crude mathematical formulas.  Steven Sittig, RRT, described it best in his article, "Neonatal Mechanical Ventilation Support:"
"Few clinicians today would remember an early model Bourne BP 200.  To set the To set a respiratory rate on this model, the clinician had to set the inspiratory time and then calculate the inspiratory-to-expiratory-time ratio (I-E) for the desired rate.Then the RT had to move theI-E ratio knob to the approximate ratio, watching to avoid a red light on the display that signaled an inverse I-E ratio. Finally, the clinician had to check the ventilator rate using a watch.   (23)
I personally don't remember this ventilator, but my first job as an RT had a Baby Bird as the back up ventilator, and even after I was instructed on how, I prayed I never had to use it:  it was very intimidating.  Just the idea of using a calculator and watch to set up a ventilator seemed so old fashioned.  After looking at that vent I was happy for new technology.

Sechrist Infant Ventilator
Early 1970s:  Sechrist infant IV 100B:  A pneumatically powered, single circuit, O2 blender, continuous gas flow,

1976:  Bourns Electric Adult Respirator (a.k.a. the Bear 1)

It was a hugely vertical rectangular blue ventilator with simple control knobs on the front interface.  The ventilator was updated twice during the 1980s as the Bear 2 and Bear 3.  A Bear Cub was also marketed for the infant market to replace the previous Bourn infant respirators on the market and compete with newer IMV infant electric ventilators.  Several other Bear products have since been introduced to the market, including the Bear 33 in the 1990s, the Bear 1000 Adult/ Pediatric Ventilator in 1992, and the Bear Cub 750 VS Ventilator in 1996.

1978:  Stylets:  The idea of using a stylet inside an ETT to assist with intubation was first used in 1978.  The first stylets were central venous catheters, yet later stylets were manufactured specifically for modern disposable PVC plastic ETTs, of which come in a variety of sizes.

1980:  Synchronized Intermittent Mandatory Ventilation:  This was basically an improved version of IMV that allowed the ventilator to better "synchronize" the spontaneous and the mechanical breaths to make being on a ventilator more comfortable for an awake patient, and to prevent the patient from "bucking" or "fighting" the ventilator.  The lower the respiratory rate the more spontaneous breaths the patient was allowed.  The mode also required ventilators to be more sensitive to recognizing the patients desire to take spontaneous breaths.  (24xxxx)

References:  (under construction)
  1. Szmuk, et 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, reference to page 227
  2. Szmuk, ibid
  3. The Wood Library Museum, "Mueller-Morch Piston Respirator,",, accessed March 2, 2012. 
  4. Kishen, Roop, chapter 2, "Perceptions, Perspectives and Progress:  Intensive Care 50 years on," of the text, "Critical Care Update 2010," 2011,  page 7, edited by Roop and Vineet Nayyar
  5. Wyka, Kenneth A., Paul J. Mathews, William F. Clark, ed., "Fundamentals of Respiratory Care," 2002, . page 630, Section IV, Essential Therapeutics
  6. Wyka, ibid
  7. Sills, J.R.,  "Modifying IPPB Therapy," Respiratory Care Certification Guide, 1994, second edition, St. Lois, Mosby.
  8. Gedeon, Andras, "Science and Technology in Medicine," 2006, page 450-51, Carl-Gunner Engstrom
  9. ippbHess, Dean R., et al, "Respiratory Care:  Principles and Practice," 2012, "Intermittent Positive Pressure Breathing," chapter 18, page 370
  10. ippbStephen, Phyllis Jean, "Nebulization Under Intermittent Positive Pressure," The American Journal of Nursing," 1957, Sept., vol. 57, No. 9, pages 1158-1160
  11. ippbStephen, ibid
  12. ippbHess, Dean R., et al, "Respiratory Care:  Principles and Practice," 2012, "Intermittent Positive Pressure Breathing," chapter 18, page 370
  13. ippbWyka, op cit
  14. QQ  Holand, J. et al, "Historical Note:  Keuskamp and Amsterdam Infant Ventilator," Anesthesia, 2006, 1, pages 65-71
  15. Branson, Richard,  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
  16. "Company History," Puritan Bennett Corporation,, accessed February 27, 2012
  17. "About us:  Respiratory Products for nearly a century,",, accessed February 27, 2012
  18. "About us:  History of Ventilation,",, accessed February 27, 2012
  19. "The Servo Story:  Thirty Years of Thechnological Innovation Evolving with Clinical Development of Ventilatory Treatment Strategies,",, accessed February 27, 2012
  20. "The Servo Story...," ibid
  21. Sittig, Steven E, "Neonatal Mechanical Ventilation Support," AARC Times, April, 1999, page 51
  22. xxxxxxSmith, B.E., C.D. Hanning, "Advances in Respiratory Support," British Journal of Anesthesia, 1986, 58, pages 1380150 
xxxxxx Smith, B.E., C.D. Hanning, "Advances in Respiratory Support," British Journal of Anesthesia, 1986, 58, pages 1380150

yyyyyyyyy Klein, J.J., et al, "Pulmonary function after recovery from the adult respiratory distress syndrome," Chest, 1976, 69, pages 350-55

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