When dentist lays back the chair close to or past horizontal, i feel something block my airway near back of throat. can no longer benefit from nitrous as cannot take in air through nose. anxiety is high and i have stopped my dental visits. who help?

You should discuss this with your dentist. Do you have the same issue when lying down in bed, horizontally? You really should be breathing through your nose during dental visits to avoid gagging. Terminating your dental visits is not the answer.

Make Dentist aware of your problem. Ask Dentist to not lean you back as far.

You may have a large tongue, and possibly a palatal and/or mandibular lingual tori (a bone growth in the middle palate or at lingual of mandible). A large tongue couple with a large palatal tori may block your air way. If patient is given local anesthesia, the numbness of the tongue and palate will make it worse. Further complication occurs if the patient could not breath through his nose.