"Pain of colonoscopy almost took my breath away"

I had a colonoscopy where I asked for no sedation as I felt more than able to put up with some "wind like" discomfort as described in the patient information leaflet I received. I felt under pressure by the staff to have sedation and the reason given to me was "that it helps you to relax", so I agreed to a small amount. The pain I felt for the first five or so minutes of the procedure was so intense it almost took my breath away. I was left feeling shocked and traumatised. I felt that the nursing staff didn't comfort or reassure me constantly throughout the procedure (which I think they are supposed to do) and this just added to my distress. I complained to the hospital hoping for a genuine apology, some validation for my feelings and a promise that lessons would be learned. Instead I felt the reply was confrontational, contained inconsistencies and I have been left feeling 100% worse. I really thought the hospitals response should have placated me and made me feel better. I think someone needs to read the NHS constitution regarding complaints! I believe someone should look into the whole issue of colonoscopy pain. I've read so much about this issue, so I know it’s happening. I would suggest that patients should be given questionnaires so that these types of procedures can be audited.