Give new Fed Chair Janet Yellen this — she certainly knows how to break the tension in a room of economists during a financial crisis.

In a Fed meeting on Sept. 16 — the day after Lehman collapsed and the US economy was on an express ride to the Great Recession — Yellen, then the San Francisco Fed boss, used an odd barometer to note that the economy was slowing.

“East Bay plastic surgeons and dentists note that patients are deferring elective procedures,” she said, referring to a San Francisco Bay neighborhood.

The comment elicited laughs from her male counterparts, a transcript of the hearing, released Friday, reveals.