To the Editor:--Several reports suggest that intraperitoneal insufflation with carbon dioxide moves the tracheal carina cephalad during laparoscopic cholecystectomy. [1,2]This phenomenon may result in bronchial intubation. However, the distance the carina moves cephalad is unknown. The current report examined chest roentgenograms before and after carbon dioxide insufflation during laparoscopic cholecystectomy to measure the distance between the carina and the tip of the endotracheal tube.

Ten adult patients (ASA physical status 1-2) undergoing laparoscopic cholecystectomy were studied. Their age (mean+/-SD) was 50.0+/-12.1 yr (range 34-76 yr), their weight was 58.1 +/-12.2 kg (range 44.0-77.0 kg), and their height was 156.9 +/-7.6 cm (range 146.0-165.5 cm). Four of the patients were men, and six were women. Our institutional committee approved this study, and all patients provided informed consent.

All patients received 0.01 mg/kg atropine sulfate and 1 mg butorphanol tartrate intramuscularly 1 h before entering the operating room. Anesthesia was induced with thiamylal, isoflurane, and vecuronium bromide. After tracheal intubation, with patients supine, a first chest roentgenogram was taken while keeping airway pressure stable at 10 cmH2O. Subsequently, general anesthesia was maintained with 33% O2/N sub 2 O, isoflurane (1.0-1.5%), and controlled ventilation with tidal volume of 10 ml/kg, respiratory rate of 10 breaths/min, inspiratory:expiratory ratio of 1:2, and no positive end-expiratory pressure. Fifteen minutes later, arterial blood was collected. After these procedures, intraperitoneal insufflation began, and the carbon dioxide insufflation pressure was maintained around 10 mmHg. After completion of abdominal insufflation, a second chest roentgenogram was taken during the same conditions as those for the first roentgenogram (airway pressure at 10 cmH2O). Also 15 min after insufflation, arterial blood gases were measured. PaO2and PaCO2before and after insufflation were compared. Cardiothoracic ratio (CTR), the distance between the lower edge of the first thoracic vertebral body and the left or right vertex of the diaphragm (Lt Dis T-D, Rt Dis T-D, respectively), and the distance between the tracheal carina and the tip of the endotracheal tube (Dis C-E) were compared before and after insufflation by chest roentgenograms. Data are presented as mean+/-SD. The results were statistically analyzed by Wilcoxon's signed-rank test for paired data or the Mann-Whitney U test for unpaired data (Stat View SE + Abacus).

As a result, PaO2and PaCO2were 158 +/-42 mmHg and 33+/-4 mmHg and 160+/-30 mmHg and 38+/-3 mmHg, before and after insufflation, respectively. Abdominal carbon dioxide insufflation did not affect PaO2(P = 0.879), but PaCO2increased significantly (P = 0.013). Table 1shows the individual results from the chest roentgenograms before and after insufflation. CTR increased from 53.4+/-4.5% to 57.1 +/-5.0% (P = 0.005). Lt Dis T-D and Rt Dis T-D were 19.4 +/-1.8 cm and 18.8+/-2.1 cm and 16.4+/-2.3 cm and 15.6+/-2.4 cm, before and after insufflation, respectively (P = 0.005). Dis C-E was 3.4+/-1.6 cm and 2.3+/-1.5 cm before and after insufflation, respectively (P = 0.005) and decreased by 1.1+/-0.4 cm.

Table 1. Results from the Chest Roentgenogram before and after Insufflation

Table 1. Results from the Chest Roentgenogram before and after Insufflation
Table 1. Results from the Chest Roentgenogram before and after Insufflation

In conclusion, the current study reveals that 10 mmHg CO2insufflation pressure during laparoscopic cholecystectomy shifts the tracheal carina cephalad by 1.1+/-0.4 cm. This result suggests the need for reassessment of tracheal tube position after abdominal insufflation.

Hiroshi Iwama, M.D., Director of Anesthesiology and Emergency Medicine.

Masaki Nakane, M.D., Staff Anesthesiologist.

Kennichi Aoki, M.D., Staff Anesthesiologist.

Kazuhiro Watanabe, M.D., Associate Director of Anesthesiology.

Takami Komatsu, M.D., Staff Anesthesiologist.

Toshikazu Kaneko, M.D., Staff Anesthesiologist, Central Aizu General Hospital, 1-1 Tsuruga-machi, Aizuwakamatsu City, Fukushima Prefecture, 965 Japan.

Hamm P, Lang C, Fornecker ML, Bruant P, Vuillemin F: Recurrent selective bronchial intubation in laparoscopic cholecystectomy. Ann Fr Anesth Reanim 1993; 12:67-9.
Morimura N, Inoue K, Miwa T: Chest roentgenogram demonstrates cephalad movement of the carina during laparoscopic cholecystectomy. ANESTHESIOLOGY 1994; 81:1301-2.