California recently discovered that 170 of its ventilators arrived broken, disputing the claim from the Department of Health and Human Services that all of the ventilators shipped by the Federal Emergency Management Agency were ready to use. The agency said in a statement that problems with some ventilators were limited to the devices’ external batteries, and that federal officials were quick to assist the states with any technical issues.

Federal officials revealed on Wednesday that their stockpile of medical gear was nearly depleted. FEMA has shipped 26 million surgical masks, 11.6 million respirator masks and more than five million face shields to states, setting off a race to obtain millions of recently produced masks from a variety of manufacturers at a moment of huge price spikes for respirators that previously sold for about 85 cents.

The bigger struggle, however, has focused on ventilators because states have asked for tens of thousands more than the approximately 9,400 that the U.S. government currently has in its stockpile. The Defense Department is also making 1,065 ventilators available, although those require special training and are not used as frequently in hospitals.

As White House officials have for the first time looked at a supply they had not thought about, they have discovered it is not only far smaller than what they need — it is also in constant need of maintenance.

Aric Vacchiano, the vice president of U.S. sales and services at Vyaire Medical in Chicago, which produces the LTV 1200, one of the ventilators in the federal stockpile, said the company had been fielding calls from all over the country as hospital officials rushed to get the machines in working order.

“They’re reaching out in every direction,” Mr. Vacchiano said.

Vyaire was responsible for maintaining some of the ventilators in the federal stockpile until that contract ran out in late August. The company protested when a broader contract to keep the stockpile up-to-date was granted to Agiliti instead. The dispute was not resolved until January, when Agiliti again prevailed.

It then received thousands of ventilators — it would not say how many — for restoration, and that work is still underway.