A 2.2 percent increase in Medicare payment rates to hospitals for 1987 under the new prospective payment system was recommended Tuesday by the Prospective Payment Assessment Commission (Pro-Pac), a special study group set up by Congress to advise the Department of Health and Human Services on the issue.

The 2.2 percent figure contrasts sharply with the tentative 0.5 percent increase announced by Secretary of Health and Human Services Otis R. Bowen May 29. The Pro-Pac recommendation could provide ammunition for the hospital industry in its campaign to persuade Congress to overturn Bowen's lower rate on grounds that a higher increase is needed to make up for inflation and other factors.

Pro-Pac adopted the 2.2 percent recommendation by a 10-to-5 vote. Under the law, the secretary is required to consider but not necessarily accept Pro-Pac's recommendation. The hospital industry hopes to persuade Congress to mandate a larger increase, perhaps 2 percent, as part of a budget reconciliation bill.

Hospital industry sources say each one percent increase is worth $400 million.

An attempt to persuade Congress to extend up to 10 years the HHS' proposal for a four-year transition to a new reimbursement system for capital outlays will also be made when the reconciliation bill comes before the Ways and Means Committee.