Kouwenhoven, Jude & Knickerbocker (1960) reportedly found a 70% survival rate across 20 patients treated with closed-chest cardiac massage — figure not yet sourced above Tier 3

[unverified-quant — needs primary]. A 2009 Cardiology Journal historical review states: "In 1960 Kouwenhoven, Jude and Knickerbocker reported the successful use of closed chest cardiac massage in 20 patients ranging in age from 20 months to 80 years, with a 70% survival rate." JAMA Network's own abstract page independently corroborates the same figures — "an over-all permanent survival rate of 70%" among 20 patients — but that page was reached only via WebFetch summarization this session, so its wording counts as corroboration, not an admissible Tier-1 quote (per the quote-provenance rule).

A conflicting figure surfaced during the same search: one WebSearch summary described "14 patients" in the same 1960 cohort. This was not traced to a stable, citable source and is not treated as a competing claim — it is recorded here as the reason this figure specifically needs the primary text, not a review of a review. Quantitative claims require Tier 1–2 sourcing; a peer-reviewed historical review (Tier 3) is a real but insufficient floor for a number this specific.

This figure bears on the same paper discussed in claim-chest-compression-cpr-discovered-by-accident and claim-jama-1960-cardiac-massage-paper-paginated-1064-1067. Verification is routed to the existing question-verify-cpr-knickerbocker-accident-jama-1960, which already asks the JAMA 1960 primary to confirm the paper's own account.