CAPNOGRAPHY MONITORING IS BENEFICIAL BY ESTIMATING ETCO2 INSTABILITY DURING ENDOSCOPIC SUBMUCOSAL DISSECTION (ESD)

Aims:

Endoscopic submucosal dissection (ESD) requires deeper sedation than mucosal resection. This may lead to adverse ventilation problems. Capnography measures end-tidal CO2 (EtCO2) levels and it is known to detect depressed respiratory activity prior to the incidence of hypoxic events. However, its usefulness during endoscopy has been disputed. Considering that absolute EtCO2 value monitoring would not be as effective as that of general anesthesia due to belching or body movements during endoscopy, we herein introduced a concept of 'EtCO2 instability', and studied whether it is correlated with higher chance of hypoxia.

Methods:

Between January 2017 and June 2018, 98 patients scheduled to ESD had received pulmonary function tests before the procedure. All patients received capnographic monitoring in addition to conventional monitoring. EtCO2 level was recorded every 1 minute. Sedation Index was calculated by assessing M/OAAS (Modified Observer's Assessment of Alertness/Sedation) score, tachypnea and spontaneous body movements. Patients were later grouped into 'Normal' and 'Hypoxia' groups according to intra-procedural presence of hypoxia and their demographic, procedural characteristics were comparatively analyzed.

Results:

By multivariate logistic regression, we analyzed several factors that influenced the incidence of hypoxic events, and EtCO2 instability (OR 2.427, P-value 0.001) was among them. Hypoxia and EtCO2 instability have been shown to share same causal factors such as high Mallampati score, intra-procedural oral respiration and lower baseline SpO2.

Conclusions:

EtCO2 instability is related to incidence of hypoxic events during ESD. Monitoring EtCO2 is helpful since increased instability of EtCO2 on the monitor may precede a potential hypoxic event, so that clinicians can respond more promptly. In groups of patients who have high Mallampati score or obstructive lung function it may be beneficial to be routinely monitored by EtCO2 when performing ESD.