Real-time B-mode ultrasound imaging was performed in 24 intubated patients in order to confirm the correct placement of endotracheal tubes. The large acoustic impedance mismatch between the air within the endotracheal tube cuff and the tracheal wall could be bypassed by (1) use of a foam-cuffed Bivona endotracheal tube, or by (2) cuff inflation with saline instead of air. Optimal repositioning of the endotracheal tube could be done under direct visualization. Imaging of the foam-filled and saline-filled cuffs was easier in the longitudinal (sagittal) than in the transverse view, was enhanced by a slight longitudinal to-and-fro motion of the tube, and was often improved with the use of a stand-off pad. Cases of esophageal intubation were not considered. Use of a noninvasive imaging modality such as ultrasound will spare selected patients from the radiation exposure associated with a chest x-ray. This is of value in pregnant patients and in those requiring frequent chest radiographs for the sole purpose of confirming correct endotracheal tube placement. Limitations of the techniques are discussed.

No abstract

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.

The increase in the BUB amplitudes in the distal insertion pathway suggests that, at least with a 2.5-MHz transducer, an approximate 1.5-cm US window exists in most cases, by which close approach of the ventral marrow-cortex interface could be anticipated. Other ratios may serve as stop criteria to prevent further drilling. A precipitous drop in BUB amplitude may be an indication of a cortex perforation.

Image-processed three-dimensional volume-rendered MNR scans, which allow visualization of the entire brachial plexus within a single composite image, have educational value in illustrating the complexity and individual variation of the plexus. Suggestions for improved guidance during infraclavicular block procedures are presented.