End tidal carbon dioxide measurement using an electro acoustic sensor.

End tidal carbon dioxide measurement with an electro-acoustic sensor is demonstrated. The sensor consists of an acoustic resonator coupled to a low cost electro-acoustic element. By simultaneous measurements with a reference sensor, the new device was tested on subjects performing exercise, hypo- and hyperventilation whereby the CO<inf>2</inf>concentration ranged from 2.1 to 7.0 kPa. The output from the experimental device correlated well with the reference CO<inf>2</inf>readings with a correlation coefficient of 0.976. Response time for expiration less than 0.8 seconds was noted. The new device could be useful in situations where selectivity to other gases is not important.