On the eve of what is expected to be a landslide victory for a fourth term in Congress, Rep. Gladys Spellman remained in a semi-comatose state, struggling to survive the cardiac arrest that felled her last week during a campaign appearance at a Laurel shopping mall.

Michael Schwartz, a cardiologist who has been treating the Democratic congresswoman at the Greater Laurel-Beltsville Hospital, said yesterday that Spellman, 62, has shown further slight signs of improvement -- she was able to take a breath without the aid of a respirator -- but she was still in critical condition and unable to emerge from her "sleep-like state" or open her eyes, talk or in any way signify that she has not suffered brain damage.

Schwartz said he could not predict when or if Spellman would emerge from her semi-coma, which he said was caused by a "shock to her nervous system" that occurred during her collapse at a Halloween costume contest at Laurel Centre. As part of the effort to pull Spellman from semi-consciousness, hospital authorities said that family and aides of the three-term congresswoman are taking turns sitting by her and whispering encouragement.

"The capacity of the nervous system to recover is tremendous," Schwartz said, adding that it is possible, although somewhat unusual, for a patient to remain in Spellman's state for an extended period of time but still recover.

However, if Spellman's brain was deprived of blood and oxygen for more than three minutes as a result of the collapse and the heart stoppage, the likelihood of a complete recovery could be quite limited.

According to several accounts, when Spellman collapsed around 6:30 Friday night, she was immediately given cardio-pulmonary resuscitation by several persons standing nearby, but no one knows if those efforts were able to restore enough of a heart beat to keep blood and oxygen flowing through her brain. A rescue unit with equipment to restore a heart beat did not arrive until about 16 to 20 minutes after Spellman collapsed on the mall floor, according to witnesses.

Hospital spokesmen said Spellman has responded to some basic tests of her reflex reactions and from this doctors have determined that she is aware of her surroundings and not completely unconscious. If Spellman does show signs of further neurological improvement within the next week, doctors will conduct more sophisticated tests of her brain functions.

Medical sources not involved with the case said yesterday that if a patient remains in a semi-comatose state for longer than about 24 hours the likelihood of brain damage is generally considered to be increased.

While concern remained great for Spellman's neurological condition, Schwartz said that her other bodily functions, including her heart and kidneys, were functioning normally, and her pulse and blood pressure remained strong yesterday.