| abstract |
A unique ingestible and retrievable ambulatory esophageal monitor for colorimetric analysis of ambient pH within selected portions of the esophagus comprising a nasoesophgeal conduit at least one generally transparent semi-permeable envelope carried proximal the distal end of the conduit for positioning within the distal esophagus. The envelope contains an ion exchange color indicator composition comprised of a weak cation exchange substance selected from the group comprising a resin, a cellulose or an agarose and intermixed and bound therein being an indicator dye preferably either methylene blue or azure A. The ion exchange substance having a disassociation potential (pK) of at least 4 so that the indicator dye selectively disassociates causing the envelope to visually discolorize when exposed to a clinically significant ambient pH of 4 or less within the esophagus. |