Because of such problems, an F.D.A. reviewer recommended against the approval of Multi-Med’s application, even though the company planned to use a special color and label to distinguish it as a feeding tube, according to internal agency documents provided to The Times. Dr. Kevin McBryde, the F.D.A. reviewer, wrote in an April 20 memorandum that the Multi-Med application “does not adequately address the safety concerns for misconnections.”

An F.D.A. manager overruled Dr. McBryde, saying Multi-Med’s tubing was no more dangerous than tubes already on the market. The manager’s reasoning was based on the agency’s own rules for an abbreviated device-approval process that requires only that the manufacturer prove that a new product works just like an old one, whether the old one is safe or not. No clinical testing or proof of safety is generally needed.

The result of these rules is that the F.D.A. sometimes approves devices even when officials suspect that they might harm or kill patients. Indeed, the F.D.A. has on occasion approved a new device, mandated that it be recalled and then approved another just like it because the rules are set up to require such approvals.

In 2005, for instance, the French company Gambro was forced to recall its Prisma dialysis machine because patients died or were injured after the patients or caregivers ignored warnings from the machine and, as a result, received too much or too little fluid. In 2007, Edwards Lifesciences of California sought approval for the Aquarius system, a dialysis machine that an agency reviewer noted had the same problem.

The agency had never rescinded its original approval of the Gambro device; such approvals are rarely rescinded, even after a recall, partly because there is some debate about whether it would be legal to do so. So the agency approved the Edwards one as well, documents show. In February, the Edwards device was recalled because of “reports of clinically significant fluid imbalance,” according to the recall alert.

“I raised this issue during the review, but the division director at the time advised that the device should be” approved, wrote Joshua Nipper, an F.D.A. device reviewer, in a Feb. 18 internal e-mail provided to The Times. “We knew that the device could result in serious injury or death, and we allowed it to be marketed anyway. Not surprisingly, the device causes serious injury / death and now must be recalled.”