Doctors caring for Hamlin said his ability to communicate with his family after a cardiac arrest boded well for his recovery.

The University of Cincinnati Medical Center has been treating Mr. Hamlin since he collapsed on the field. He still has a lot of work to be done.

There are reasons to believe that Mr. Hamlin may be on a path to recovery, but there are still questions about his health.

In a news conference on Thursday, Dr. Knight and Dr. Timothy A. Pritts said that Mr. Hamlin was in an intensive care unit and unable to speak. He can now say something by shaking his head. He asked his nurse if she had won the game.

Dr. Knight and Dr. Pritts did not know why Mr. Hamlin went into cardiac arrest during the game. They haven't ruled out the possibility that he had incredibly bad luck when he collided with the receiver. The blow can cause the heart to stop if it happens at the right moment in the heart's cycle.

The consequences can be dire even if the person is resuscitated and his heart is revived.

There is no blood flow to the brain in a cardiac arrest.

It is not possible to do a complete neurological evaluation while Mr. Hamlin is on a respirator. There is very little chance of severe neurological damage.

There are many reasons to think that he will return to normal function.

ImageA crowd of players, coaches and other football personnel is gathered on the field of a football stadium at nighttime, with fans still in the stands and an ambulance at the crowd's edge at right.
Players prayed around the spot where Mr. Hamlin had fallen on Monday.Credit...Joshua A. Bickel/Associated Press
A crowd of players, coaches and other football personnel is gathered on the field of a football stadium at nighttime, with fans still in the stands and an ambulance at the crowd's edge at right.

Recovery is not instantaneous. The phase where patients are slow to process and respond in conversation is called the slow phase.

Acute respiratory distress syndrome, also known as ARDS, is a serious injury that can be caused by a cardiac arrest. Half of people who had cardiac arrest developed the condition.

The compressions of the chest wall can cause lung injuries. It is possible for patients to breathe stomach fluids into their lungs. Lung injury can be caused by the impaired blood flow during cardiopulmonary resuscitation.

Mr. Hamlin was involved in a problem.

The professor of critical care medicine at the University of Pittsburgh Medical Center said there is no specific treatment for ARDS. It can take days or weeks for a patient to heal.

Some patients have scar tissue in their lungs. For many, the scar tissue is not serious, but for a world-class athlete, it is.

Dr. White said that scars become a concern when someone is on a ventilator. Mr. Hamlin has been on a breathing machine.

Getting him to breathe on his own will be the next big milestone.

Mr. Hamlin's doctors didn't say when or if he would be able to play football again, or if he would recover in time. They said they were taking their time.

It has been a long road for the last few days. He said that Mr. Hamlin was sick.

He said that he is now showing signs of good neurological recovery.