Honda Accord A/C dash controls

I own a 1998 honda accord, 4 cylinder with 243K miles. I'm experiencing a problem where the fan is blowing quite well, and yet the air is not coming through the vents as it should. I tried using the dash controls to switch from face, to feet, to windshield defroster. The only option that seems to be working properly is the defroster for the windshield. Very little to no air is coming through the face vents even with the fan clearly blowing and turned up to the max. What might the problem be?

Marlon