External chest compression restoring circulation was demonstrated in animals and humans decades before Kouwenhoven's 1958 'accidental' discovery

Floor: Tier 3–4 acceptable for historical claims when uncontested; the general shape here is corroborated by two independent sources, though they disagree on specific names and years.

Two independent secondary historical reviews agree that closed/external chest compression restoring circulation was demonstrated in animals decades before Kouwenhoven's Johns Hopkins group. A 2009 Cardiology Journal review: "The first successful use of closed chest cardiac massage in living cats is attributed to Bohem of Germany and his associates. In 1880 Niehaus performed the first unsuccessful attempt at closed chest cardiac massage in a man. Five years later, Koenig reported eight successful cases of human closed chest cardiac massage." The same review reproduces a quote from George W. Crile's early-1900s report anticipating a "thoracic pump theory": "Pressure upon the thorax alone is capable of producing an artificial circulation. This is by no means accomplished by its action upon the heart solely, but by its action upon all the large vessels: arteries, veins and capillaries together" (quoted in the review, not independently verified against Crile's own paper).

An independent 2021 Creighton University CME slide deck gives a consistent skeleton with different specific names for the human milestone: "1878: In Germany, Rudolph Boehm shows that external compressions of the heart provide adequate circulation in cats" ... "1891: After using external compressions to restart the hearts of 2 young human patients, German surgeon Dr. Friedrich Maass becomes the first to advocate chest compressions, rather than ventilation alone, to help with circulation" ... "1903: In Cleveland, Ohio, Dr. George Crile's research confirms that external chest compressions restore circulation in dogs" ... "1904: Dr. Crile reports successful closed-chest cardiac massage in 1 human case." Both sources agree Boehm's cat work is earliest, predating Kouwenhoven by roughly 80 years; they disagree on which named clinician made the pivotal human application (Niehaus/Koenig vs. Maass) and the exact year (1885 vs. 1891). That divergence is recorded rather than silently resolved.

This rhymes with a separate, already-documented antedating in the same lineage: Ferris et al.'s 1936 paper credits Prevost and Battelli's 1899 work, not Kouwenhoven's, as the first report of shock-induced recovery from fibrillation. Both the counter-shock/defibrillation lineage and the chest-compression/CPR lineage now have an older forgotten precedent standing behind the name the vault first learned.

The Creighton deck also states, uncited within itself, that "1933: Researchers at Johns Hopkins University[] rediscover external compressions when they find that pressure on a dog's sternum provides adequate circulation to the brain ... confirmed in more than 100 dogs" — a specific, striking detail (an internal Hopkins precedent 25 years before the 1958 "accident," within the same institution) that is not carried as a claim here because the source itself gives it no citation.