Invasive CO2 monitoring with arterial line compared to end tidal CO2 during peroral endoscopic myotomy

Abstract

Abstract Background and study aims Peroral endoscopic myotomy (POEM) has become a recognized treatment for achalasia. The technique requires CO2 insufflation. It is estimated that the partial pressure of CO2 (PaCO2) is 2 to 5 mm Hg higher than the end tidal CO2 (etCO2), and etCO2 is used as a surrogate for PaCO2 because PaCO2 requires an arterial line. However, no study has compared invasive and noninvasive CO2 monitoring during POEM. Patients and methods Seventy-one patients who underwent POEM were included in a prospective comparative study. PaCO2 plus etCO2 was measured in 32 patients (invasive group) and etCO2 only in 39 matched patients (noninvasive group). Pearson correlation coefficient (PCC) and Spearman’s Rho were used to calculate the correlation between PaCO2 and ETCO2. Results PaCO2 and ETCO2 were strongly correlated: PCC R value: 0.8787 P ≤ 0.00001, Spearman’s Rho R value: 0.8775, P ≤ 0.00001. Within the invasive group, the average difference between PaCO2 and ETCO2 was 3.39 mm Hg (median 3, standard deviation 3.5), within the 2- to 5-mm Hg range. The average procedure time (scope in to scope out) was increased 17.7 minutes (P = 0.044) and anesthesia duration was 46.3 minutes. Adverse events (AEs) included three hematomas and one nerve injury in the invasive group and one pneumothorax in the noninvasive group. There were no differences in AE rates between the groups (13 % vs 3 % P = 0.24). Conclusions Universal PaCO2 monitoring contributes to increased procedure and anesthesia times without any decrease in AEs in patients undergoing POEM. CO2 monitoring with an arterial line should only be performed in patients with major cardiovascular comorbidities; in all other patients, ETCO2 is an appropriate tool.