Monday, May 9, 2016

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 was an important time in our history, because without it we might probably still be stuck with primitive medicine.

This era was particularly important to the evolution of asthma, as all the theories regarding it, old and new, were hotly debated.  Some physicians were dogmatic, holding on to one particular theory for dear life, while others were more open minded.  Either way, the fact that the disease was openly discussed in the arena of ideas allowed physicians to better understand this disease.

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.
During the course of the 19th century there were eleven theories regarding asthma that were hotly debated.  Some were ancient ideas, and some were new.  The most prevalent of these theories are listed here. 
  1. Humoral theory of asthma:  This theory postulates 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. More specifically, Galen believed asthma was caused by an over abundance of phlegm.
  2. Dyspnea theoery of asthma:  That asthma and dyspnea are the same thing was established by Hipporates.  Basicallly 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. Symptomatic theory of asthma:  Many physicians believed asthma was nothing more than a symptom of some other malady, such as heart, lung or kidney disease.  Sometimes the cause remained mysterious.  
  4. Bronchitic theory of asthma:   Wheezes and dyspnea depend on obstruction of the air tubes by the inflammatory products of bronchitis. This results in excessive mucus production. Dyspnea is less severe and more constant than a paroxysm of asthma. 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, and we might think of it today as bronchitis.  
  5. Spasmotic/ convulsive theory of asthma Convulsions, Contractions or spasms of the muscles that line the bronchioles are a main component of asthma.  Celsus defined asthma as being 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 century fine tuned it.  It was a hotly contested theory during the 19th century. 
  6. Nervous theory of asthma:  The belief that asthma is nervous in origin, or caused by things that influence the mind -- such as strong emotions like laughter, crying, stress, excessive happiness, excessive sadness, a yearning for the mother, etc -- goes back to the ancient world. Physicians early on observed no organic lesions in asthmatic lungs, and therefore assumed it must be nervous in origin.  They observed asthma was intermittent, sometimes with long intermissions between paroxysms.  This theory the nerves caused spasms in the lungs was introduced to the medical community in the 16th century by Jan 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. 
  7. Paralytic theory of asthma:  Asthma is caused by paralysis of the respiratory muscles and this results in dyspnea.  This idea was first established by Dr. Rene Laennec around around 1810 or 1820.  "Bronchial muscles," he said, "are paralyzed and dyspnea is expiratory, more more constant, and less spasmotic."  We might now refer to this as emphysema. (1, page 37)
  8. Diaphragmatic spasm theory of asthma:  This theory postulates that tonic spasms of the diaphragm causes asthma.  This theory may have been devised by examining the way asthmatic people breath, and was probably proposed by Thomas Willis and Neumaun (?).  It was also later supported by (M. Alton) Wintrich in the mid 19th century, and later confirmed by Heinrich von Bamberger around 1870.
  9. 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 was often referred to as a type of asthma.
  10. Reflex theory of asthma:  This theory postulated that 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, which responds by causing the airways to contract.  For example, catarrh or inflammation of the nose can cause spasm of the muscles of the lungs by reflex action.  Most who support this theory believed some form of disturbance in the blood was the result.  Other causes of this might be a response from the urea, disturbance of metabolism, dyspepsia, etc. However, some who support this theory believed it was just an extehnsion of the nervous theory of asthma.
  11. 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. This is a theory that has recently gained momentum.
  12. Other:  Yes, lots of other theories existed.  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 said, "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.
Of all the theories regarding asthma during this era, Orville Brown said in 1917 in 1917:
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)
For the most part, each physician had a favorite theory, found evidence to support it, and adjusted the definition slightly as evidence indicated.

So, what theory won the era? 

  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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