cholera in 1849 and the biopsychosocial model: historical analysis or anachronism? the snowflakes of...
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Cholera in 1849 and the Cholera in 1849 and the Biopsychosocial Model: Biopsychosocial Model:
Historical Analysis or Historical Analysis or Anachronism?Anachronism?
The Snowflakes of MSU:Peter Vinten-Johansen
Howard Brody
Nigel Paneth
Steve Rachman
Michael Rip
The ArgumentThe Argument
One can draw useful analogies between: – Today’s biopsychosocial model of
human health, and – The scientific approaches used by John
Snow to study both cholera transmission and inhalation anesthesia in 1846-56?
The Argument--IIThe Argument--II
The BPS modelJohn Snow and his careerMethods of studying anesthesiaMethods of studying cholera
transmissionSnow’s theoretical synthesis (“continuous
molecular changes”)
Engel, 1977: BPS ModelEngel, 1977: BPS Model
Systems (part-whole relations)Multilevel hierarchy (atoms to
biosphere)“Ripple effects” among levelsPatterns of information flow
(feedback loops)Anti-reductionistic
BPS: SourcesBPS: Sources
General systems theory (von Bertalanffy, Laszlo)– Cybernetics (von Neumann),
information theory, game theory“Holistic” biology (Dubos, Mayr)All grounded in mid-20th-century
thought
John Snow: Early LifeJohn Snow: Early Life
Born 1813, YorkFather: Laborer/farmerMother: IllegitimateApprentice in Newcastle, 1827-32Cared for coal miners in 1831-32 cholera
epidemic
John Snow: Life (cont.)John Snow: Life (cont.)
Newcastle medical school, 1832-34Assistant, Newcastle and Yorkshire,
1834-36Walked to London (via Bath), 1836Hunterian school and Westminster
Hospital, 1836-38MRCS/LSA, 1838General practice, Soho, 1838
John Snow: Later lifeJohn Snow: Later life Active in Westminster Medical Society MD, Univ. of London, 1844 Begins anesthetic research and practice, 1847 On the Mode of Communication of Cholera, 1849 Attends Queen Victoria, 1853, 1857 Broad Street Pump, 1854 President, Medical Society of London, 1855 Completes On Chloroform, 1858 Death of apoplexy, 1858
Snow on EtherSnow on Ether
Dec. 1846: Sees ether used in LondonJan. 1847: Displays data on relation
between concentration and temperature; working on apparatus
September 1847: Publishes On Ether, 80 cases, describes degrees of anesthesia
How?How?
Snow’s research, 1838-46, ideally prepared him for ether:– Studies of respiration and asphyxia– Studies of chemistry and physics of gases– Properties of inhaled medications and
poisons– Design of new apparatus
Snow’s Approach to EtherSnow’s Approach to Ether
Chemical level: problem in defining physics and chemistry e.g. concentration-temperature relationships
Physiological level: animal experiments with different concentrations of gases
Clinical level: correlate bedside observations with animal experiments to predict degrees of anesthesia
Ether and ChloroformEther and Chloroform
Define a class of agents with similar properties (“narcotism”), of which anesthesia only one effect
Calculate precise serum concentrations of agent when inhaled at given concentration in air
Correlate serum concentration with clinically observed effects
Hardly anyone else doing this work in 1847-58
Snow and Cholera: 1848-9Snow and Cholera: 1848-9
Cholera must be communicable person-to-person based on geographic distribution
A local affection of alimentary canal; dehydration produces systemic symptoms
Assumed to be inhaled by lungs– why must this be true?
Snow’s TheorySnow’s Theory
Causal agent of cholera ingestedMultiplies in gut Causes symptoms of disease by irritating
mucous membraneShed in evacuationsHousehold spread: dirty handsArea spread: drinking water
Budd, Brittain, Swayne 1849Budd, Brittain, Swayne 1849
Microscopic particle must cause cholera
Therefore must search for evidence at microscopic level
Identified “cholera fungus”Identification quickly refuted
Snow, 1849Snow, 1849
Molecular
Cellular
Organ/System
Household
Community
“Continuous molecular changes”(self-replication of vital processes)
Can’t identify agent; analogy toova of intestinal worms
Irritation > Diarrhea > Dehydration
Spread by poor hygiene
Spread by contaminated drinkingwater
Snow on Cholera, 1849Snow on Cholera, 1849
Move from levels where “collateral sciences” least developed to levels allowing better tools for investigation
Ova of worms: analogy of functional properties
Cf. “Cholera fungus”: identified a structure but had no idea of function
Cholera Deaths per 10,000 Cholera Deaths per 10,000 Households (Snow, 1855)Households (Snow, 1855)
0
10
20
30
40
50
60
70
80
Lambeth Co. Southwark & Vauxhall Co.
(first weeks of epidemic)
Snow’s Method, 1849-1855Snow’s Method, 1849-1855
Ultimately discovered that statistics was a sounder basis for investigation than microscopy
Reasoned across levels to deduce likely effects at neighborhood and community levels
Then gathered data to confirm or disconfirm hypotheses
Continuous Molecular Continuous Molecular Changes, 1853Changes, 1853
CMC, 1853CMC, 1853
Annual oration to Medical Society of London
Rare opportunity to speak at theoretical-speculative level
Opportunity to link (successful) anesthesia research with (so far rejected) cholera theory
CMC, 1853-- IICMC, 1853-- II
“Molecular” = smallest level of organization, “insensible” (very small) distances between particles acting on each other
“Change” = constant flux at molecular level in either living or non-living matter (common chemical basis of vital and non-vital)
CMC, 1853--IIICMC, 1853--III
“Continuous” = molecular processes peculiar to living things; never commence anew without continuity with previous processes of same type
Combustion/oxidation– a bridging process, exists in both living and non-living matter
Anesthesia: Counter-AffinityAnesthesia: Counter-Affinity
A B
C
C exerts pull on A and prevents A from combining with B,without itself combining
Anesthesia TheoryAnesthesia Theory
C = anesthetic agentA <-> B = oxidation process
responsible for maintaining consciousness and sensation
Reversible interference with normal bodily process
CMC and Epidemic CMC and Epidemic DiseasesDiseases
Causative agent of disease enters bodyBy CMC, replicates itself inside bodyHijacks normal body processes of
oxidation, etc. to support its own replication
Disruption of normal body processes causes symptoms of disease (irreversible in extreme cases)
““Communication”Communication”
“Mode of Communication” of epidemic diseases
“Communication” among molecules accounting for continuity of vital processes– infections agents as packets of information (computer viruses?)
Social and cultural communication as analogous flows of information
The communication of certain molecular changestaking place in the brain is by no means confined to…parents and offspring, but extends collaterallyin all directions, by means of vibrations in the air…If the brain of an animal is in a particular state ofmolecular action, from any object that excites fearor joy, it may cause a similar state in the brain ofothers of the species, by uttering a cry or merelyassuming a particular demeanour.
The faculty of speech gives man a power ofcommunicating his complex feelings and ideas, far exceeding that of lower animals; and theinvention of literature has greatly increased this power in civilized nations. By speech, not onlycan fresh sensations and ideas be communicated,but also that continuation of them calledremembrance, by which they revive after, it may be a long interval of suspended animation.
Snow’s Social VisionSnow’s Social Vision
According to Snow, his oration “On Continuous Molecular Changes” was itself an example of continuous molecular change in human organisms and human society
Both chemical and social processes viewed as governed by patterns of information flow (“communication”)