Earl Wood

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Professor Earl H. Wood, MD, PhD
Earl Wood in his office at the Mayo Clinic with an inset photo from 1946 showing him in Heidelberg, as part of operation paperclip, seeking to recruit German scientists to work in the United States.
Born (1912-01-01)1 January 1912
Mankato, USA
Died 18 March 2009(2009-03-18) (aged 97)
Rochester, Minnesota
Residence Rochester, Minnesota
Citizenship United States
Nationality United States
Fields Cardiovascular, Respiratory, Aerospace Medicine and Cardiovascular and Pulmonary Dynamics
Institutions Mayo Clinic
Rochester, Minnesota
Alma mater Macalester College
University of Minnesota
Thesis The Distribution of Electrolytes and Water Between Cardiac Muscle and Blood Serum with Special Reference to the Effects of Digitalis (1942)
Known for Invention of the G-suit, Development of cardiac catheterization into a clinical service, Invention of the ear oximeter, Co-inventor of the first dynamic (high speed) volumetric x-ray computed tomography system
Influences Aerospace Physiology, Cardiovascular Monitoring, Cardiovascular Dynamics, Medical Instrumentation
Notable awards Presidential Certificate of Merit from Harry Truman-1947; Macalester College honorary degree of D.Sc.-1950; Distinguished Citizen Award-1974; honorary member of the Royal Netherlands Academy of Arts and Sciences-1977; honorary member American College of Cardiology - 1978; honorary degree, doctor of medicine, from the University of Bern, Switzerland - 1978; Humboldt Prize for Senior U.S. Scientists by the government of West Germany - 1979; John Phillips Memorial Award of the American College of Physicians - 1979; President of the American Physiological Society - 1980-81; President of the Federation of American Societies for Experimental Biology (FASEB) - 1981-82; Ray G. Daggs Award for his distinguished long-term service to the science of physiology and, in particular, to the American Physiological Society - 1995; Street in Rheinfelden, Germany dedicated as "Earl H. Wood Strasse" - 2002.
For the school superintendent in Maryland, see Earle B. Wood.

Earl H. (Howard) Wood, M.D, Ph.D. (c. January 1, 1912 – March 18, 2009) was a cardiopulmonary physiologist who helped invent the G-suit and much more.[1][2][3]



Shortly after receiving an M.D. and PhD in physiology from the University of Minnesota medical school under the mentorship of Professor Maurice B. Visscher, MD,[4] Wood became a key member of a team, working in a, what was then top secret, laboratory at the Mayo Clinic, tasked with helping military pilots and flight crew survive and function in high G-force environments. Based upon extensive physiologic testing via use of the human centrifuge installed at the Mayo Clinic, it was determined that blackout and then unconsciousness was caused by reduction of blood flow to the eyes first and then the brain.[5] The solutions the team arrived at were the M-1 breath hold maneuver[6][7] and the G-suit.[8][9] The M-1 maneuver consisted of a strained exhalation effort against a closed glottis designed to increase left ventricular pressure. The G suit was a garment, produced by the David Clark Company, which has air bladders situated at the calves, thighs, and abdomen of the wearer. The bladders inflate as the G-force acting on the aircraft increase, constricting the wearer's arteries, hence increasing blood pressure and blood flow to the brain.

The G-suit was a superior solution to another alternative (a water-filled suit) being tested at the time, which was considered impractically heavy and cumbersome. The water-filled, pulsatile pressure suits were developed to effect venous return. However, Wood and colleagues' detailed physiologic measurements demonstrated that what was required was augmentation of arterial pressure.

Wood himself regularly tested the flight suits, taking many turns in a human centrifuge and plane dubbed the "G-wiz." He calculated that over his several hundred rides, he had lost consciousness for an aggregate of at least fifteen minutes (without any observed lasting damage). Wood was awarded a Presidential Certificate of Merit by Harry Truman in 1947.

The G-suit was adopted in the 1940s. The current models are based on the pattern Wood and his colleagues designed. Following World War II, Wood was recruited to participate in what was known as "Operation Paperclip"[10] The goal was to keep the top German scientists away from Russia and working for the United States.

In 1962, Wood was the tenth scientist to be named "Career Investigator," of the American Heart Association.[11] These funds allowed Wood considerable flexibility in regards to the directions of his research.

Other work[edit]

After his work on the G-Suit, Wood worked on techniques for measuring cardiac blood flow. He was granted a patent for the ear oximeter, an optical instrument that measures blood oxygen levels without taking blood by examining the variation of light absorption as a function of oxygen saturation of hemoglobin. Integral to the work leading to the development of the G suit was the perfection of vascular catheterization methods needed to understand the distribution of blood pressure and flow. Shortly after the end of World War II, open-heart surgery emerged with the Mayo contribution[12] to the development of the heart-lung bypass machine initially developed by Gibbons[13] and perfected by Wood and colleagues.[12][14] Wood's work at the Mayo Clinic lead to the development of many technologies[15] allowing for the assessment of the heart and lungs including dye dilution methods serving to characterize cardiac output,[16] methods for the assessment of central blood volume,[17] the calculation of pulmonary vascular resistance (known as the "Wood Unit" and calculated by subtracting pulmonary capillary wedge pressure from the mean pulmonary arterial pressure and dividing by the cardiac output),[18][19][20] analog subtraction angiography, and eventually the Dynamic Spatial Reconstructor (DSR), a predecessor to modern high speed volumetric computed tomography (CT) allowing for the evaluation of the beating heart and breathing lungs. The DSR comprised 14 X-ray tubes and a hemicylindrical fluorescent screen imaged by 14 associated television cameras.[21][22]

In all, Wood is noted for his contributions (together with members of the Biodynamics Research Unit (BRU), under his direction, within the Physiology and Biophysics Department at the Mayo Clinic) in the following areas:

  • methods for protection against blackout and unconsciousness during high G-forces[23][24][25]
  • methods for heart catheterizations;[26][27]
  • methods for monitoring vascular pressures;[28][29][30]
  • the pulse oximeter for real time non-invasive monitoring or arterial oxygen saturation;[31][32]
  • methods for calculation of pulmonary vascular resistance (Wood Unit);[18][19][20]
  • methods for the digital conversion of analog physiologic signals allowing for computer-based monitoring of vascular signals (using the early computer developments of IBM which was just down the road from Wood’s laboratory);[15]
  • methods for liquid fluorocarbon respiration explored for protection against high G forces expected during rocket launch and re-entry while leaving and returning to earth’s atmosphere in space exploration;[33][34]
  • methods for the assessment of pleural pressure to determine regional gravitational effects on the lung;[35][36][37][38][39]
  • indicator dilution curve methodology for the assessment of cardiac output and other physiologic derivative;[40][41][42]
  • indocyanine green dye for use in the indicator dilution method;[43][44]
  • analog subtraction angiography for the assessment of cardiac structures via video fluoroscopy[45][46][47][48] and
  • the earliest predecessor (The Dynamic Spatial Reconstructor)[49][50][51][52] of modern high speed, multi-source / multi-detector row computed tomography for the non-invasive imaging of the beating heart and breathing lungs.

Wood's publication list, with more than 700 entries, is a testament to the number of fellows who trained under him and who became prominent researchers in their own right.

Early life[edit]

Earl Wood was born to Inez Goff and William Clark Wood in Mankato, Minnesota on January 1, 1912 and started life on a subsistence farm.[3] William Wood, in addition to farming, was a real estate businessman. Earl Wood earned a B.A. in Mathematics and Chemistry from Macalester College in 1934, and his MD degree and a PhD degree in physiology from the University of Minnesota. Earl was one of 5 brothers (Earl, Chester, Delbert, Harland and Abe) and a sister, Louise.


All of Earl Wood's siblings grew up to be highly accomplished.[11] Louise A. Wood was awarded the Medal of Freedom by President Truman for her services as over-seas director of the American Red Cross during World War II. and became the executive director of the Girl Scouts of the USA from 1961-1972. Harland G. Wood was the first director of the Department of Biochemistry at the School of Medicine and Dean of Sciences, Case Western Reserve University. As a biochemist, he was notable for proving in 1935 that animals, humans and bacteria utilized carbon dioxide[53] and received the National Medal of Science. Chester was a teacher and a university administrator; Delbert was, in succession, a lawyer, an Federal Bureau of Investigation agent, and a railway executive; Abe was an internist and founder of a Colorado-based medical clinic. Not surprisingly, in 1950, Earl Wood's mother, Inez, was awarded the title of "Minnesota Mother of the Year."[11] Earl and his wife, Ada, had a daughter, Phoebe and three sons, Mark, Guy and E. Andrew.


  1. ^ Pearce, Jeremy (March 26, 2009). "Earl H. Wood Is Dead at 97; Helped Invent G-Suit". The New York Times. Retrieved March 27, 2009. 
  2. ^ https://www.wsj.com/articles/SB123819290677361041
  3. ^ a b Bonde, Bill; Bonde, Karen. Inventing the G-suit: The Life Story of Dr. Earl Wood. 
  4. ^ Fox, JJ (September 1976). "Maurice B. Visscher at seventy-five--a life in the service of humanity". Circ Res. 39 (3): 295–296. doi:10.1161/01.res.39.3.295. PMID 782741. 
  5. ^ Wood, EH; Lambert, EH (September 1946). et al.. "Effects of acceleration in relation to aviation". Fed Proc. 5: 327–344. PMID 20999477. 
  6. ^ WOOD EH. Use of the Valsalva maneuver to increase man's tolerance to positive acceleration. Fed Proc. 1947;6(1 Pt 2):229. PubMed PMID 20342926.
  7. ^ WOOD EH, HALLENBECK GA. Voluntary (self-protective) maneuvers which can be used to increase man's tolerance to positive acceleration. Fed Proc. 1946;5(1 Pt 2):115. PubMed PMID 21066535.
  8. ^ WOOD EH, LAMBERT EH. The effect of anti-blackout suits on blood pressure changes produced on the human centrifuge. Fed Proc. 1946;5(1 Pt 2):115. PubMed PMID 21066536.
  9. ^ LAMBERT EH, WOOD EH. The problem of blackout and unconsciousness in aviators. Med Clin North Am. 1946 Jul;30(4):833-44. PubMed PMID 20992942.
  10. ^ Hansel, Jeff (27 October 2008). "INSIDE Inventor had a life outside of science". Post-Bulletin. 
  11. ^ a b c Burchell HB. Earl H. Wood: outstanding twentieth century investigator of the heart and circulation. Clin Cardiol. 1987 May;10(5):372-4. PubMed PMID 3297443.
  12. ^ a b Kirklin, JW; Dushane, JW; Patrick, RT; Donald, DE; Hetzel, PS; Harshbarger, HG; Wood, EH (May 18, 1955). "Intracardiac surgery with the aid of a mechanical pump-oxygenator system (gibbon type): report of eight cases". Proc Staff Meet Mayo Clin. 30 (10): 201–206. PMID 14371757. 
  13. ^ Stokes, TL; Gibbon, JH Jr. (August 1950). "Experimental maintenance of life by a mechanical heart and lung during occlusion of the venae cavae followed by survival". Surgery, gynecology & obstetrics. 91 (2): 138–156. PMID 15442833. 
  14. ^ Gibbon, JH (1954). "Application of a mechanical heart and lung apparatus to cardiac surgery". Minn Med. 37 (3): 171–185. PMID 13154149. 
  15. ^ a b Ritman, EL (November 1, 2014). "Earl Wood--a research career noted for development of novel instruments driven by the power of the indicator dilution concept". J Appl Physiol. 117 (9): 945–956. doi:10.1152/japplphysiol.00491.2014. PMID 25190740. 
  16. ^ Grace, JB; Fox, IJ; Crowley, WP Jr; Wood, EH (November 1957). "Thoracic-aorta flow in man". J Appl Physiol. 11 (3): 405–418. PMID 13480951. 
  17. ^ Bowers, D; Shepherd, JT; Wood, EH (May 1955). "A constant-rate indicator-infusion technic for the measurement of central vascular volume in man". Can J Biochem Physiol. 33 (3): 340–348. doi:10.1139/o55-045. PMID 14364323. 
  18. ^ a b Connolly, DC; Kirklin, JW; Wood, EH (September 1954). "The relationship between pulmonary artery wedge pressure and left atrial pressure in man". Circ Res. 2 (5): 434–440. doi:10.1161/01.res.2.5.434. PMID 13190627. 
  19. ^ a b Swan, HJ; Burchell, HB; Wood, EH (July 1959). "Effect of oxygen on pulmonary vascular resistance in patients with pulmonary hypertension associated with atrial septal defect". Circulation. 20 (1): 66–73. doi:10.1161/01.cir.20.1.66. PMID 13663195. 
  20. ^ a b Shepherd, JT; Wood, EH (May 1959). "The role of vessel tone in pulmonary hypertension". Circulation. 19 (5): 641–645. doi:10.1161/01.cir.19.5.641. PMID 13652355. 
  21. ^ Ritman EL, Kinsey JH, Robb RA, Gilbert BK, Harris LD, Wood EH. Three-dimensional imaging of heart, lungs, and circulation. Science. 1980 Oct 17;210(4467):273-80. PubMed PMID 7423187.
  22. ^ Robb RA, Sinak LJ, Hoffman EA, Kinsey JH, Harris LD, Ritman EL. Dynamic volume imaging of moving organs. J Med Syst. 1982 Dec;6(6):539-54. PubMed PMID 7183727.
  23. ^ Wood EH. Contributions of aeromedical research to flight and biomedical science. Aviat Space Environ Med. 1986 Oct;57(10 Pt 2):A13-23. Erratum in: Aviat Space Environ Med 1987 Jul;58(7):706. PubMed PMID 3778400.
  24. ^ Wood EH. Development of anti-G suits and their limitations. Aviat Space Environ Med. 1987 Jul;58(7):699-706. PubMed PMID 3304268.
  25. ^ Wood EH. Development of methods for prevention of acceleration induced blackout and unconsciousness in World War II fighter pilots. Limitations: present and future. Physiologist. 1987 Feb;30(1 Suppl):S27-30. PubMed PMID 3550843.
  26. ^ Burchell, HB; Wood, EH (February 1, 1950). "Remarks on the technic and diagnostic applications of cardiac catheterization". Proc Staff Meet Mayo Clin. 25 (3): 41–48. PMID 15404372. 
  27. ^ Burchell, HB; Helmholz, Jr., HF; Wood, EH (February 11, 1953). "Over-all experiences with cardiac catheterization". Proc Staff Meet Mayo Clin. 28 (3): 50–57. PMID 13014125. 
  28. ^ Ellis, EJ; Gauer, OH; Wood, EH (March 1951). "An intracardiac manometer: its evaluation and application". Circulation. 3 (3): 390–398. doi:10.1161/01.cir.3.3.390. PMID 14812668. 
  29. ^ Wood, EH; Leusen, IR; Warner, HR; Wright, JL (July 1954). "Measurement of pressures in man by cardiac catheters". Circ Res. 2 (4): 294–303. doi:10.1161/01.res.2.4.294. PMID 13172871. 
  30. ^ Wood EH. Evolution of instrumentation and techniques for the study of cardiovascular dynamics from the Thirties to 1980, Alza lecture, April 10, 1978. Ann. Biomed. Eng. 1978 Sep;6(3):250-309. PubMed PMID 367231.
  31. ^ Wood, EH; Geraci, JE; Groom, DL (March 1948). "Photoelectric determination of blood oxygen saturation in man". Fed Proc. 7 (1 Pt 1): 137. PMID 18934670. 
  32. ^ Wood, EH; Geraci, JE (March 1949). "Photoelectric determination of arterial oxygen saturation in man". J Lab Clin Med. 34 (3): 387–401. PMID 18113925. 
  33. ^ Sass, DJ; Ritman, EL; Caskey, PE; Banchero, N; Wood, EH (April 1972). "Liquid breathing: prevention of pulmonary arterial-venous shunting during acceleration". J Appl Physiol. 32 (4): 451–455. PMID 4503080. 
  34. ^ Sass, DJ; Nolan, AC; Wood, EH (January 1974). "Digital computer analysis of circulatory and respiratory pressures in water-immersed dogs breathing liquid in force environments of 1 and 7 G". Aerosp Med. 45 (1): 1–11. PMID 4521228. 
  35. ^ Banchero, N; Schwartz, PE; Tsakiris, AG; Wood, EH (August 1967). "Pleural and esophageal pressures in the upright body position". J Appl Physiol. 23 (2): 228–234. PMID 6031193. 
  36. ^ Rutishauser, WJ; Banchero, N; Tsakiris, AG; Wood, EH (June 1967). "Effect of gravitational and inertial forces on pleural and esophageal pressures". J Appl Physiol. 22 (6): 1041–1052. PMID 6027051. 
  37. ^ Rutishauser, WJ; Banchero, N; Tsakiris, AG; Edmundowicz, AC; Wood, EH (September 1966). "Pleural pressures at dorsal and ventral sites in supine and prone body positions". J Appl Physiol. 21 (5): 1500–1510. PMID 5923220. 
  38. ^ Hoffman, EA; Behrenbeck, T; Chevalier, PA; Wood, EH (September 1983). "Estimation of regional pleural surface expansile forces in intact dogs". J Appl Physiol Respir Environ Exerc Physiol. 55 (3): 935–948. PMID 6355027. 
  39. ^ Hoffman, EA; Ritman, EL (1987). "Heart-lung interaction: effect on regional lung air content and total heart volume". Ann. Biomed. Eng. 15 (3-4): 241–257. doi:10.1007/bf02584282. PMID 3662146. 
  40. ^ Warner, HR; Wood, EH (September 1952). "Simplified calculation of cardiac output from dye dilution curves recorded by oximeter". J Appl Physiol. 5 (3): 111–116. PMID 12990551. 
  41. ^ Shepherd, JT; Bowers, D; Wood, EH (May 1955). "Measurement of cardiac output in man by injection of dye at a constant rate into the right ventricle or pulmonary artery". J Appl Physiol. 7 (6): 629–638. PMID 14381340. 
  42. ^ Hetzel, P; Swan, HJ; Ramirez de Arellano, AA; Wood, EH (July 1958). "Estimation of cardiac output from first part of arterial dye-dilution curves". J Appl Physiol. 13 (1): 92–96. PMID 13563349. 
  43. ^ Fox, IJ; Wood, EH (December 7, 1960). "Indocyanine green: physical and physiologic properties". Proc Staff Meet Mayo Clin. 35: 732–744. PMID 13701100. 
  44. ^ Edwards, AW; Isaacson, J; Sutterer, WF; Bassingthwaighte, JB; Wood, EH (November 1963). "Indocyanine green densitometry in flowing blood compensated for background dye". J Appl Physiol. 18: 1294–1304. PMC 2997752Freely accessible. PMID 14080764. 
  45. ^ Williams, JC; Sturm, RE; Tsakiris, AG; Wood, EH (May 1968). "Biplane videoangiography". J Appl Physiol. 24 (5): 724–727. PMID 5647655. 
  46. ^ Sturm, RE; Wood, EH (November 1968). "The video quantizer: an electronic photometer to measure contrast in roentgen fluoroscopic images". Mayo Clin Proc. 43 (11): 803–806. PMID 5711440. 
  47. ^ Greenleaf, JF; Ritman, EL; Wood, EH; Robb, RA; Johnson, SA (March 1974). "Dynamic computer-generated displays of data from biplane roentgen angiography for study of the left ventricle". Ann. Biomed. Eng. 2 (1): 90–105. doi:10.1007/bf02368088. PMID 4596338. 
  48. ^ Smith, HC; Sturm, RE; Wood, EH (August 1973). "Videodensitometric system for measurement of vessel blood flow, particularly in the coronary arteries, in man". Am J Cardiol. 32 (2): 144–150. doi:10.1016/s0002-9149(73)80112-2. PMID 4578631. 
  49. ^ Wood, EH; Ritman, EL; Robb, RA; Harris, LD; Ruegsegger, P (May 1977). "Noninvasive numerical vivisection of anatomic structure and function of the intact circulatory system using high temporal resolution cylindrical scanning computerized tomography". Med Instrum. 11 (3): 153–159. PMID 875764. 
  50. ^ Johnson, SA; Robb, RA; Greenleaf, JF; Ritman, EL; Lee, SL; Herman, GT; Sturm, RE; Wood, EH (March 1974). "The problem of accurate measurement of left ventricular shape and dimensions from multiplane roentgenographic data". Eur J Cardiol. 1 (3): 241–258. PMID 4613557. 
  51. ^ Wood, EH (August 1985). "The dream of a dynamic, high-fidelity, synchronous, volumetric imaging system and the road to its realization". Herz. 10 (4): 183–192. PMID 3899883. 
  52. ^ Ritman, EL; Robb, RA; Harris, LD (1985). Imaging Physiological Functions: Experience with the Dynamic Spatial Reconstructor. Greenwood Publishing Group. ISBN 0030693527. 
  53. ^ Wood HG, Utter MF. The role of CO2 fixation in metabolism. Essays Biochem. 1965;1:1-27. Review. PubMed PMID 4880809.