UTILITY OF MONITORING CAPNOGRAPHY, PULSE OXIMETRY, AND VITAL SIGNS INTHE DETECTION OF AIRWAY MISHAPS - A HYPEROXEMIC ANIMAL-MODEL

This study was undertaken to determine the time interval for changes i n end tidal CO2, oxygen saturation (SaO(2)), heart rate (HR), and bloo d pressure (BP) in response to an acute airway obstruction or hypophar yngeal extubation in a hyperoxemic model. Complete and partial airway obstructions were simulated with complete and partial cross-clamping o f an endotracheal (ET) tube in five anesthetized, nonparalyzed, mechan ically ventilated Yorkshire minipigs with initial PaO2 of >400 mm Hg. Placement of the ET tube into the hypopharynx was performed to simulat e accidental extubation. Both sidestream (SS) and mainstream (MS) capn ography were used. Continuous pulse oximetry monitored SaO(2), femoral arterial catheter monitored systolic BP, and electrocardiograph monit ored HR. The time intervals for the capnograph wave to flatten and for the monitor to display zero were recorded after each airway alteratio n. The time interval to a change in the initial HR of 10 beats/min, a change of initial systolic BP of 10 mm Hg, and a change of initial SaO (2) of 5% were recorded. Experiments were carried out for 180 seconds, and 25 trials were performed. HR, systolic BP, and SaO(2) did not cha nge for the 180-second duration of the trials. Complete obstruction pr oduced a flattening of the SS and MS waveform in 8 +/- 2 seconds and 6 +/- 2 seconds, respectively. The SS and MS monitors displayed zero in 19 +/- 1 seconds and 68 +/- 7 seconds, respectively. Partial obstruct ion did not produce flattening of the wave or a monitor displaying zer o. Hypopharyngeal extubation produced a flattening of the SS and MS wa veform in 7 +/- 1 seconds and 7 +/- 2 seconds, respectively. The SS an d MS monitors displayed zero in 18 +/- 3 seconds and 76 +/- 16 seconds , respectively. Continuous end-tidal CO2 capnography detects acute air way obstruction and hypopharyngeal extubation more rapidly than does p ulse oximetry or vital sign monitoring in a hyperoxemic porcine model. (Am J Emerg Med 1998;16:350-352. Copyright a 1998 by W.B. Saunders Co mpany).