Saturday, February 04, 2012

History of spirometry (the pulmonary function test)

John Hutchinson (1811-1861)
If you're an asthmatic chances are your doctor has had you perform a pulmonary function test (PFT).  The Mayo Clinic states this is a test that measures how much air you can blow in and out, and it's a good test to help your doctor diagnose asthma or to monitor the course of your asthma over time.

During this test you blow into a spirometer which measures your lung volumes, and it's for this reason PFT testing is more historically referred to as spirometry.  Over the past 30 years I've performed hundreds of these tests, and while my PFTs now are relatively normal, once when I was about 14 I had a PFT test show I had only a 35 percent lung function (obviously it was during an asthma attack).

The first known recorded spirometry test was performed by Greco-Roman physician Claudius Galen way back in the period of 129-200 A.D.  He had a boy blow into and out of a bladder, and he found that the volumes exhaled do not change over time.  Yet Galen wasn't able to measure the volumes, he simply used his keen eye and observation, according to Ann Kiraly in her 2005 award winning article, "History of Spirometry." (1)

While others may have performed similar experiments nothing significant was recorded until Giovannin Alfonso Borelli (1608-1679)  had a volunteer plug his nose to assure an accurate measurement of lung volumes, and to prevent air from escaping or entering from the nose.  He is believed to be the first person to have have a patient block the nose, a technique that is still done to this day during spirometry testing. (2)

In 1679 Borelli became the first to measure the amount of air entering the lungs.  He did this by sucking liquid up a tube.  (3)  In 1790 James Watt invented the gasometer, a container that stores gas, that permitted "Thomas Beddoes (1760-1808) to to lay the foundation of pneumotherapy."  (4, page 29)  Beddoes used his research to found the "Pneumatic Institute at Clifton for the treatment of disease by inhalation.  (5, page 336)

In 1793 John Abernathy developed a method of collecting expired gas over mercury and attempted to determine how much those gases had been used up by the body.  He thought this was important because exhaled oxygen should be less than what is inhaled.  He also determined that exhaled oxygen would be higher in patients with certain lung diseases. (2)

He also measured a vital capacity (VC) of  3110.   (2)  Vital capacity is the total amount of air one can exhale from the lungs after a full inspiration. A VC of 3110 may have been normal for that person, considering a normal VC is now determined to be 4-5 liters.

Figure 2 -- Davey's Gasometer* *(4)
In 1800 Sir Humphrey Davey (1778-1829), assistant to Beddoes, used the gasometer of Watt to measure various lung volumes.  He measured his own vital capacity at 3110 ml. (2 and 5)

He measured his tidal volume at 210 ml.  Tidal volume (VT) is another word for normal breath. A VT seems kind of low, although it may have been normal based on Davey's height and age. (4)

He also calculated his residual volume to be about 600 ml.  (4)  Residual volume (RV) is the amount of air that stays in your lungs after a normal exhalation. It's physiologically necessary to prevent your alveoli from collapsing.  Alveoli are microscopic baloon-like structures at the end of air passages, and by keeping a little air in them at all times it's easier for them to be re-opened when you inhale.  It's kind of like the first time you try to blow up a balloon it's harder than the second time.  So, in this way, residual volume is good and normal.

Figure 3 -- Lung Capacity Chart -- 1903 (1, page 27)
To put these volumes into perspective, VC = RV + TV.  While the technique used is now different, these same volumes are measured by today's spirometers.  (See Figure 3)  Davey also devised a mechanism to determine how much oxygen was utilized by the body and how much carbon dioxide his body created.  (2)

In the following years many others performed similar experiments.  Herman Boerhaave (1668-1738) "measured the difference in the level of water in his bath tub during the two phases of respiration,"   according to Paul Lois Tissier in his 1903 book "Pneumotherapy: Including Aerotherapy and Inhalation Methods and Therapy. (4)

Davy and several others collected air in a bell-jar filled with water.  So there were various techniques performed by a variety of physicians and scientists from the 1660s to 1840s where attempts were made to measure lung volumes.  Yet it wasn't until 1846 that an effective spirometer was invented, and the inventor given credit is John Hutchinson. (4, page 29)

By this time it was well known among the medical community what the normal lung volumes were and the physiological advantages of being able to measure them.  It was known that the respiratory capacity varied with age and height, and that the respiratory capacity continues to increase until about the age of 20, and that the vital capacity of men was "considerably more" than women. (4, page 28)

Hutchinson's Spirometer
Tissier explained that Hutchinson "taught the importance of physiologic research and devised the instrument which bares his name."  Basically Hutchinson's spirometer is a combination of techniques used by other inventors who existed before him.  For example, his consisted of a bell jar immersed in water.  (4)

Tissier explained Hutchinson's spirometer this way:  "The jar hung in cords which pass over pulleys attached to two vertical supports, is counterbalanced by weights. The air, first expired by a mask applied to the patient's mouth, is conducted through an external rubber tube and then through a metallic tube in the interior of the reservoir to the upper portion of the bell jars.  As soon as expiration takes place, the air enters the jar and the later rises.  The distance transversed by the jar is read on a graduated scale, and the volume of expired air is then calculated." (4, page 29)

Schnepf (4, page 30)
Hutchinson determined that the volume of exhaled air (VC) has a linear relationship with height.  As we now know, the taller a person the longer the lungs, and the more air they can hold.  In other words, he was right.  

Hutchinson also invented a portable spirometer "where respiratory capacity is measured by the movement of a pointer."  By the turn of the 19th century Hutchinson's model had been modified "but a little."  (4, page 29)

The most significant adjustment to this device was made by Dr. Wintrich in 1856 who adjusted the bell jar so that it was movable and supported by a single rod.  Most experts believed Wintrich's improvements made the Hutchinson's spirometer much more accurate and much more easy to use. (4, page 29)

Kiraly explained that Wintrich was also the first to determine that the best way to measure VC can be estimated by a measurement of a person's height, age and weight.  This same measurement is used to this day. (2)

Various other spirometers were invented in the following years.  In 1854 Boudin created a spirometer that was more convenient but less accurate.  In 1856 Schnepf connected the bell jar to chain, "the links of which are of equal lengths so as to compensate for variations in the weight of the jar, according as it is immersed to a greater or lesser depth in the water of the reservoir." (4, page 30)

In 1856 Bonnet invented Bonnet's Apparatus, which "used an ordinary gasometer for a spirometer."  Yet Tissier recommends not using this device because it uses pressure to measure changes in lung volumes, and it may well be confused with the various pressure devices he describes later in his book (a post on these will be published on 8/5/14).

Another alternative was the Barnes Dry Spirometer, which was "Within a closed cylinder of metal is placed a rubber bag, which, when inflated, pushes up an index rod graduated to show cubic inches."  (4, page 32) This device was introduced in 1865. (6, page 894)

And there were many other variations of the spirometer over the next decades.  (4, page 32)

Boudin's Respirator (4, page 30)
So the spirometer has been modified many times through the years since Hutchinson's invention, yet the only significant changes are that graphics are now used and the bell jar is smaller.  Oh, and we should also note the system has now been computerized.

Either way, spirometry, often referred to as pulmonary function testing (PFT),  remains a significant test used to help physicians diagnose and monitor the course of disease.

Barnes Dry Spirometer (4, page 32)
  1., "History of Spirometry and Lung Function Test,
  2. Kirally, Ann, "History of Spirometry,", Journal of Pre-health Affiliated Students, JPHAS, Winter 2005, Volume 4, Issue 1,  
  3. Brockbank, E.M., ed., "The Medical Chronicle: A Monthly Record of the Progress in Medical Science," October 1905 to March 1906, Vol. XLIII, Boston, page 301,
  4. Tissier, Paul Lois, "Pneumotherapy: Including Aerotherapy and Inhalation Methods and Therapy," 1903, Philadelphia,  page 29)  Herman Boerhaave (1668-1738) 
  5. Garrison, Fielding Hudson, "An introduction to the history of medicine," 3rd ed., 1922, Philadelphia, W.B. Saunders
  6. "Commissioner of Patents," "Executive Documents printed by order of the House of Representatives during the first session of the thrity ninth congress," 1865-6, 16 volumes, Washington, Government Printing Office
  7. *Pictures compliments of JPHAS
Further readings:
  1. You can read more about some of the 19th century spirometers and even see some pictures by clicking here.  
  2. To read an awesome and much more precise account of the history of the spirometer check out Ann Kiraly's article ," which was a 2nd place entry in the Spring 2004 Health Science Writing Competition.  Her article was published in the Journal for Pre Health Affiliated Students and can be reached by clicking here.  

1 comment:

  1. I never ever read such type of info before this was really incredible. spirometry