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

Background

The use of carbon dioxide (CO₂) insufflation during endoscopic procedures is effective in reducing patient discomfort caused by bloating. However, transcutaneous arterial CO₂ (PtCO₂) monitoring usually is required for safety during long endoscopic procedures. To evaluate a new capnometer for monitoring end-tidal carbon dioxide (EtCO₂) concentrations and to compare PtCO₂ with EtCO₂ measured in the same patient, a prospective comparative study of EtCO₂ and PtCO₂ values measured simultaneously was designed.

Methods

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 CO₂ insufflation, and EtCO₂ and PtCO₂ 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 EtCO₂ and PtCO₂ values and the availability of EtCO₂ capnography were investigated.

Results

The mean EtCO₂ value during ESD was 34.7?±?4.5?mmHg, and the mean PtCO₂ value was 51.6?±?2.4?mmHg. There was a statistically significant correlation between EtCO₂ and PtCO₂ (r?=?0.331; P?=?0.002). Hypoxic events (<90% oxygen saturation [SpO₂]) caused by decreased respiratory rate occurred for 12 patients. In 10 (83%) of 12 events, a significant reduction in EtCO₂ was seen before the decrease in SpO₂.

Conclusions

The EtCO₂ values correlated with the PtCO₂ values, and the respiratory monitoring methods allowed earlier detection of hypoxia during ESD with conscious sedation than transcutaneous monitoring. The EtCO₂ capnometer was considered to be available for the ESD procedure with the patient under conscious sedation using CO₂ insufflation.