Capnographic monitoring for carbon dioxide insufflation during endoscopic mucosal dissection: comparison of transcutaneous and end-tidal capnometers

The use of carbon dioxide (CO(2)) insufflation during endoscopic procedures is effective in reducing patient discomfort caused by bloating. However, transcutaneous arterial CO(2) (PtCO(2)) monitoring usually is required for safety during long endoscopic procedures. To evaluate a new capnometer for monitoring end-tidal carbon dioxide (EtCO(2)) concentrations and to compare PtCO(2) with EtCO(2) measured in the same patient, a prospective comparative study of EtCO(2) and PtCO(2) values measured simultaneously was designed. The study enrolled 20 consecutive patients (18 men and two women; mean age, 70.1 years) with upper gastrointestinal neoplasms scheduled for endoscopic submucosal dissection (ESD) using conscious sedation with CO(2) insufflation, and EtCO(2) and PtCO(2) were simultaneously measured by each capnometer. Patient status was evaluated before ESD by the American Society of Anesthesiologists (ASA) physical status classification system, and eight patients were judged as class 1, nine patients as class 2, and three patients as class 3. The exclusion criteria ruled out patients with chronic obstructive pulmonary disease or ASA class 4 or 5 physical status. The correlation between EtCO(2) and PtCO(2) values and the availability of EtCO(2) capnography were investigated. The mean EtCO(2) value during ESD was 34.7 +/- A 4.5 mmHg, and the mean PtCO(2) value was 51.6 +/- A 2.4 mmHg. There was a statistically significant correlation between EtCO(2) and PtCO(2) (r = 0.331; P = 0.002). Hypoxic events (< 90% oxygen saturation [SpO(2)]) caused by decreased respiratory rate occurred for 12 patients. In 10 (83%) of 12 events, a significant reduction in EtCO(2) was seen before the decrease in SpO(2). The EtCO(2) values correlated with the PtCO(2) values, and the respiratory monitoring methods allowed earlier detection of hypoxia during ESD with conscious sedation than transcutaneous monitoring. The EtCO(2) capnometer was considered to be available for the ESD procedure with the patient under conscious sedation using CO(2) insufflation.