Acoustic reflectometry is a rapid, noninvasive method by which to determine whether breathing tube placement is correct (tracheal) or incorrect (esophageal). Reflectometry determination of tube placement may be useful in airway emergencies, particularly in cases where visualization of the glottic area is not possible and capnography may fail, as in patients with cardiac arrest.

No abstract

To determine the effect of transcutaneous electrical stimulation on the rabbit joint, we studied skin and intraarticular temperatures and pressure both before and following the stimulation in nine rabbits. An elevation in skin temperature by a mean of 0.6 degrees C (p less than 0.05) and increase in intraarticular temperature by a mean of 0.8 degrees C (p less than 0.01) was noted following the electrical stimulation. Intraarticular pressure in the stimulated joints has only a trend to increase, but not significantly. In four other rabbits, synovial tissue of the stimulated joint showed blood vessels congestion and interstitial edema. These results suggest that the analgetic effect produced by electrical stimulation on joints may partially involve intraarticular temperature and pressure alterations.

No abstract

Time–domain acoustic reflectometry generates a ‘‘one-dimensional’’ image of the interior of a cavity in the form of an area–distance profile. After patient intubation with a breathing tube, the characteristic reflectometry profile consists of a constant-area segment corresponding to the length of the tube, followed either by a rapid increase in the area beyond the carina (lung) or by a sudden decrease in the area to zero (esophagus). In the cardiac arrest setting, during mistaken placement of the breathing tube into the esophagus, followed by aggressive manual ventilation, is it possible to markedly distend the esophagus, such that the esophageal profile looks like a tracheal profile? With approval of the USC IUCAC Committee, an animal study was conducted with anesthetized, tracheally intubated, and mechanically ventilated dogs. With a separate breathing tube in the esophagus, aggressive esophageal ventilation (comparable to that seen in the cardiopulmonary resuscitation setting) was accomplished with a manual resuscitation bag. A Benson Hood Labs two-microphone reflectometer was used to obtain esophageal profiles with and without the above ventilation. In this pilot study, there was no significant esophageal distention as a result of the above ventilation. [Research supported by the Alfred E. Mann Institute.]