[Semiquantitative capnometry--helpful in verification of tube position in trauma patients?]

Severely injured patients, in particular, benefit from initiation of endotracheal intubation and controlled ventilation before hospital admission. The most frequent and most serious mishap of this emergency procedure is inadvertent esophageal tube placement. A reliable and simple determination of proper tube placement involves capnometry, the measurement of carbon dioxide concentration during the respiratory cycle. The purpose of this study was to evaluate the dependability of semi-quantitative capnometry in verifying proper tube placement in the prehospital treatment of trauma patients. First, we determined and tested the suitability of the equipment used in this study (STAT CAP) in 40 patients under controlled hospital conditions; subsequently, we tested it under prehospital conditions on 40 trauma patients. Within the two study groups, the STAT CAP proved to be of high sensitivity (1.0) and specificity (1.0) in identifying tracheal tube position immediately after intubation manoeuvre, even in patients with a shock index > 1 (n = 14) and patients with cardiac arrest (n = 3). In cases of tracheal tube position, a CO2 signal was noted after two ventilations, on average, in both study groups. The average initial CO2 value recorded amongst the hospital study group was 30-50 mmHg, against 20-30 mmHg in the prehospital trauma group. The traditional signs used to verify endotracheal tube placement (direct visualization of the vocal cords and auscultation of breath sounds upon the chest) failed in three cases amongst the prehospital trauma group; in all of these cases the STAT CAP detected the (tracheal) tube placement correctly. We conclude that the STAT CAP reliably detects tracheal placement of endotracheal tube in non-arrested patients. In the arrested patient, interpretation of CO2 nonappearance requires caution. In addition to the traditional clinical signs, semi-quantitative capnometry is a meaningful supplement to verify tracheal tube placement in the prehospital management of trauma patients.