Evaluation of an ambu-bag valve with a self-contained, colorimetric end-tidal CO2 system in the detection of airway mishaps: an animal trial.

OBJECTIVE: Capno-Flo (Kirk Specialty Systems, Carrouton, TX) is a portable pulmonary resuscitator (self inflating ambu-bag--valve system) with a self-contained, colorimetric end-tidal CO2 detector that has the ability to provide continuous CO2 monitoring for up to 2 hours. The purpose of this study is to determine the accuracy and time interval for the Capno-Flo monitor to detect acute airway obstructions and hypopharyngeal extubations in an intubated animal model.

SUBJECTS: Five anesthetized, non-paralyzed, mechanically ventilated Yorkshire minipigs.

METHODS: Complete and partial airway obstruction was simulated with complete and partial cross-clamping of the endotracheal (ET) tube. Placement of the ET tube into the hypopharynx was performed to simulate accidental extubation. In addition to the Capno-Flo colorimetric indicator, both sidestream (SS) and mainstream (MS) capnography were used to monitor end-tidal CO2 and comparison. The time intervals for the capnograph wave to flatten and for the monitor to display "zero" were recorded after each airway alteration. Each experiment was carried out for 180 seconds, and a total of 25 trials was performed.

RESULTS: Complete obstruction produced a color change in the Capno-Flo monitor in 9+/-2 seconds and flattening of the SS and MS waveform in 8+/-2 seconds and 6+/-2 seconds, respectively. The SS and MS monitors displayed zero in 49+/-7 seconds and 19+/-1 seconds, respectively. Partial obstruction did not produce color change, a flattening of the wave, or a monitor display of zero. Hypopharyngeal extubation produced a color change in 10+/-2 seconds, flattening of the SS and MS waveform in 7+/-2 seconds and 7+/-1 seconds, respectively. The SS and MS monitors displayed "zero" in 76+/-16 seconds and 18+/-3 seconds, respectively.

CONCLUSION: The Capno-Flo identified all complete airway obstructions and hypopharyngeal extubations rapidly. The CF monitor performed comparable to the SS and MS capnographs. Neither the Capno-Flo, nor the sidestream, nor the mainstream capnographs detected partial airway obstruction. The clinical application of this portable inexpensive capnometer in the continuous monitoring of the intubated patient, especially the transport patient, should be investigated further.