“Maybe CNN is just like an emergency room.”

That is what a longtime CNN employee theorized last year, during one of the channel’s predictable defeats in the Nielsen ratings.

When elections and explosions happen, people tune in to CNN, the same way they hurry to a hospital when they think they are having a heart attack. But people tend not to linger in either place — a reality that was reaffirmed for CNN this week when Nielsen ratings showed that April was the channel’s lowest-rated month in 10 years.

CNN, with its vast news-gathering resources and a heap of international channels, is set to make nearly $600 million in operating profit this year, a record high, for its parent company, Time Warner. But the downward ratings trend for CNN/U.S., its flagship channel in the United States, has stirred discontent within CNN and Time Warner. Performance of CNN/U.S. drives public perception — and employee pride — and declines there may gradually damage CNN’s networks as a whole.

Jeffrey Bewkes, the Time Warner chief executive, has made his dissatisfaction about the CNN/U.S. ratings known to his lieutenants and expects them to make changes, according to some of the 15 current and former CNN employees interviewed for this article. Those people, representing a wide cross-section of the channel, spoke on the condition of anonymity because they were not authorized by their bosses to talk to a reporter.