Monday, February 18, 2013

1800-1900: Eleven asthma theories

The 19th century was an "age of enlightenment" where physicians and scientists started to question old theories of medicine and come up with new ones.  This is an important time in our history, because without it we might probably still be stuck with primitive medicine.When it came to asthma, this era was very significant.

Think of it this way:
  • Before 400 B.C. asthma was just another mysterious disease caused by evil spirits or gods.
  • In 400 B.C. the Hippocratic writers defined asthma as dyspnea. 
  • Around 1700 John Fuller defined asthma as a disease entity of its own, slightly more severe than dyspnea and less severe than orthopnea 
  • During the 18th century asthma was basically believed to be a disease in some way associated with and caused by sputum.
By the year 1900, or shortly thereafter, the following were the theories supported by one physician or another.  While the first two on this list were headed out the door, surely some physicians still held on to them for dear life.  The remainder are theories debated for the eternity of the century

The 19th century theories of asthma were:
  1. Humoral theory of asthma:  That asthma was caused by an imbalance of the four humours: black bile, yellow bile, phlegm and blood.  This was the prevailing theory from about 400 B.C. (and probably sooner) when Hippocrates defined it, and the 1st century when Galen reaffirmed it, to the 19th century when scientific theories disproved it. 
  2. Dyspnea theoery of asthma:  That asthma and dyspnea are the same thing was established by Hipporates.  Basicalllly anything that causes you to be short of breath is asthma; asthma is a symptom, an entity, as opposed to a specific disease. This theory was on the way out the door by the turn of the 19th century, although was pretty much the prevailing thought until the 18th century when scientists and physicians realized there were various causes of dyspnea, and started treating asthma as a disease and not just a symptom.  
  3. Bronchitic theory of asthma:   Wheezing and dyspnea depend on obstruction of the air tubes by the inflammatory products of bronchitis. This results in excessive mucus production. (this is essentially chronic bronchitis). Dyspnea is less severe and more constant. This was the prevailing theory during the 18th century, and it made its way into the 19th century through the writings of Dr. Robert Bree.  A variation of this theory held great sway at the end of the 19th century and was referred to as the Theory of vessel turgescence.  This is basically inflammation of the mucosal membranes that line the respiratory tract.  
  4. Spasmotic/ convulsive theory of asthma:  Contraction or spasms of the muscles that line the bronchioles are a main component of asthma.  Celsus (25 B.C.-50A.D.) defined asthma is caused by "the narrow passage by which the breath escapes, it comes out with a whistle."  The theory was introduced to the medial community by Thomas Willis in 1682, and William Cullen in the next entury fine tuned it, which is why it was so hot during the 19th century.
  5. Nervous theory of asthma:  The belief that asthma is nervous in origin, or caused by things that influence the mind, such as strong emotions (laughter, crying), stress, excessive happiness, excessive sadness, a yearning for the mother, etc. This idea came about early in our history because there were no observable organic lesions or scarring in the lungs of people who suffered from it during life. Therefore, people with asthma were often burdens on society as they couldn't do things normal people do.  The idea was introduced to the medical community in the 16th century by Jean Baptiste van Helmont and Thomas Willis, and in the 18th century by William Cullen.  It was proven by the experiments of Francis Ramadge in 1835, Joseph Bergson and Amedee Lefevre win 1836, and Francis Romberg in 1841.  It was given true credibility by the writings of Henry Hyde Salter during the 1850s.  The main idea of this theory was that asthma was characterized by periodic attacks, followed by periods where the breathing was normal. 
  6. Paralytic theory of asthma:  Asthma is caused by paralysis of the respiratory muscles and this results in dyspnea (this is essentially emphysema).  This idea was first established by Dr. Rene Laennec around around 1810 or 1820.  "Bronchial muscles are paralyzed and dyspnea is expiratory, more more constant, and less spasmotic. (1, page 37)
  7. Diaphragmatic spasm theory of asthma:  That tonic spasms of the diaphragm caused asthma.  This theory may have been devised by examining the way asthmatic people breath. This theory may have first been proposed by Thomas Willis (1621-1675) and Neumaun (?).  It was also later supported by (M. Alton) Wintrich in the mid 19th century, and later confirmed by Heinrich von Bamberger (1822-1888) in around 1870.
  8. Cardiac theory of asthma:  This is the theory that asthma is caused by blood being sucked into the lungs causing congestion and dyspnea. During the 19th and early 20th centuries, it's often referred to as a type of asthma.
  9. Reflex theory of asthma:  Something other than the lungs causes it.  Eating too much or eating certain foods can effect a nerve and send a "reflex" signal to the lungs to respond. Catarrh or inflammation of the nose can cause spasm of the muscles of the lungs by reflex action.  Most who support this theory believe some form of disturbance in the blood is the result.  Other causes of this can be a response from the urea, disturbance of metabolism, etc. However, some who support this theory not it's just an extension of the nervous theory of asthma.
  10. Hay fever theory of asthma:  Hay fever leads to asthma.  Some speculate inflammation (or catarrh) of the upper airway leads to inflammation of the lower airways of the lungs, leading to bronchitis or asthma.
  11. Other:  Yes, lots of other.  Some doctors just let their imaginations fly free. Dr. Breuer, for example, "believed there was an automatic control of breathing through the vagi and that the stretching of the alveolar walls stimulates expiration and hinders inspiration. An increasing of the total lung volume, he thinks, would tend to stimulate expiration rather than inspiration." (1, page 37) Some theories may have been scientifically justified, and others, such as Breuer's, mere speculation. Other physicians noticed asthma improved after removal of polyps in the respiratory tract and sinuses.
There are also many physicians who believe asthma is not a disease at all, rather a symptoms of  some other disease process, either known (such as heart, lung or kidney disease) or unknown (mysterious).  Yet these physicians continued to stay in the minority.

Other than the bronchitic theory of asthma, most of these theories were generated either at the tail end of the 18th century or the earlier part of the 19th.  Generally, various physicians chose one or two of these theories as their favorite, and found evidence in support of that theory, adjusting the definition slightly as evidence indicated.

In 1917 Orville Harry Brown gave us a good synopsis of the above theories:  "The multitude of theories some ingenious and helpful and others far fetched and convincing evidence of a fruitless search, have failed to receive much attention."  (1, page 25)

In other words, while these seven theories were the main theories debated during this era, there were many more where that came from.  Regardless that most of the above theories started as speculation, they held significant sway at one time or another among the medical community.  

So this is the theme that leads us into the 19th century. So which of these asthma theories won the era?

References:
  1. Brown, Orville Harry, "Asthma, presenting an exposition of nonpassive expiration theory," 1917, St. Louis, C.V. Mosby Company.  The above mentioned theory of vessel turgescence comes from this reference also on page 25. 

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