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Friday, June 20, 2014

How the hypoxic drive theory was born

While oxygen was discovered as early as the 18th century, it was not routinely used therapeutically until the early 21st century.  Still, it wasn't until the 1940s that physicains started realizing their were risks associated with its use, and 1960 when the hypoxic drive theory was born.

Oxygen was discovered in 1777 by Joseph Priestley. Despite its availability, it was not routinely used to treat medical conditions mainly because there was no convenient means of producing, storing, and delivering oxygen to patients.  Yet by the turn of the 21st century the first two of these obstacles were resolved, and it was up to John Haldane to resolve the third.

In 1922, Haldane wrote about his own research on oxygen in "The Therapeutic Administration of Oxygen."  During WWI he had developed a mask to conveniently deliver oxygen to soldiers suffering from pulmonary edema due to poison gas.  After the war he continued his experiments in hospitals.

Soon thereafter oxygen tanks became more and more common at the patient bedside, and oxygen was tried on patients with pulmonary edema and pneumonia, although sometimes for patients with cystic fibrosis, asthma, emphysema and chronic bronchitis.  (7)

Once oxygen was administered to COPD patients, it was soon realized that some of these patients became lethargic and lost their drive to breathe.  It was soon learned that it was the oxygen causing this because it caused their carbon dioxide (CO2) to rise.

In 1949 a case was documented where a man with emphysema "lapsed into a coma after receiving oxygen therapy but rapidly recovered after the oxygen was removed," according to Nicola Cooper, Kirsty Forrest, Paul Cramp in their 2006 textbook, "Essential guide to acute care."

The text also explains that "in 1954 a decrease in ventilation in 26 out of 35 patients with COPD given oxygen therapy, with a rise in PaCO2 and a fall in pH.  No patient with a normal baseline PO2 showed these changes.  In a further study it was showed that stopping and starting oxygen therapy led to a fall and rise of PaCO2, respectively."  (8)

The concern became so great that in the 1950s a study was performed that ultimately lead Dr. EJM Campbell to give a lecture to pulmonologists in 1960 about the dangers of giving too much oxygen to COPD patients.  It was this lecture that forever linked hypoxic drive with COPD, and gave birth to the hypoxic drive theory.  (9)

Yet instead of a scientific theory being treated as a scientific theory it was treated as scientific fact, and this began the accepted practice of keeping patients in much need of supplemental oxygen hypoxic.

The medical profession decided the hypoxic drive theory sounded good so it must be good. The Hypoxic Drive Theory thus became the law of COPD land. Any evidence to the contrary would be rejected.

Of interest here is that the study Campbell referred to in his lecture consisted of only four COPD patients. Regardless, the theory quickly gained acceptance by the medical community, and became the gold standard when taking care of patients with COPD

Since then a few studies have confirmed the theory, although many have shed doubt on the theory.  Regardless, due to Campbell's presentation, the theory had already stuck in the minds of physicians and medical professors.  They had now become dogmatic to the theory, and closed minded to any evidence to the contrary.   (10)

  1. Schmidt, Greggory A., Jesse B. Hall M.D "Oxygen Therapy and Hypoxic Drive to Breath:  Is There Danger in the patient with COPD?" Critical Care Digest, 1989, 8, pages 52-53
  2. Wilkins, Robert L, James K. Stoller, ed. "Egan's Fundamentals of Respiratory Care," 2009, pages 309-310
  3. Caruana-Montaldo, Brendan, et al, "The Control of Breathing in Clinical Practice," Chest, 2000, 117, pages 205-225 (This article also provides a good review of the central and peripheral chemoreceptors and the drive to breathe)
  4. Wojciechowski, William V., "Entry Level Exam Review for Respiratory Care:  Guidelines for success," 3rd edition, 2011, U.S., page 487?
  5. Cooper, Nicola, Kirsty Forrest, Paul Cramp, "Essential guide to acute care," 2nd edition, 2006, Massachusettes, page 24
  6. Tines, John Hudson, "Exploring the History of Medicine," 1999, great read for obtaining a pithy history of medicine
  7. Glover, Dennis W. , "History of Respiratory therapy," 2010, page 94, great read for obtaining a pithy history of respiratory therapy
  8. Cooper, Nicola, Kirsty Forrest, Paul Cramp, "Essential guide to acute care," 2nd edition, 2006, Massachusettes, page 24
  9. Campbell, E.J.MRespiratory Failure,"  The British Medical Journal,  June 1965, 1451-1460 (article provided by link)
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