Performance of Litholyme™ compared with Sodasorb™ carbon dioxide absorbents in a standard clinical setting

Comparison of the novel membrane-based carbon dioxide filter memsorb™ with a chemical granulate absorbent using a high-fidelity lung simulator: a prospective randomized in vitro trial

PURPOSE

Memsorb™ is a novel device for carbon dioxide (CO2) removal from anesthesia circuits via a semipermeable polymeric membrane. We evaluated the performance of the memsorb device for the removal of CO2 in an Aisys™ CS2 machine and compared it with a standard chemical granulate absorber (CGA) using a high-fidelity lung simulator.

METHODS

We used an in vitro lung simulator (DUCt) to control CO2 release by imitating alveolar gas exchange. The ventilator settings were identical for all measurements. The fresh gas flow (FGF) was randomized to either 0.5 L·min-1 or 2 L·min-1, completing three trials for each FGF for either memsorb or CGA. The EtCO2 and FICO2 levels were recorded for 30 min in each setting.

RESULTS

EtCO2 was comparable between the groups with 2 L·min-1 FGF over the observation period. FICO2 was significantly higher in the memsorb group during the trial (2 L·min-1; 3.9 mm Hg; 95% CI, 4.4 to 3.3; P < 0.001). EtCO2 with 0.5 L·min-1 FGF was higher with memsorb than with CGA over the observation period (3.7 mm Hg; 95% CI, 2.7 to 4.7; P = 0.004). With 0.5 L·min-1 FGF, FICO2 was significantly higher in the memsorb group compared with CGA over the whole observation period (6 mm Hg; 95% CI, 6.4 to 5.5; P < 0.001).

DISCUSSION

CO2 was successfully removed from the anesthesia circuit. FICO2 was significantly higher with memsorb throughout the observation period. Nevertheless, the clinical impact of these observations remains unclear. Further clinical trials are required to determine the utility of the novel device.

Biological washout modelling for in-beam PET: rabbit brain irradiation by 11C and 15O ion beams

Positron emission tomography (PET) has been used for dose verification in charged particle therapy. The causes of washout of positron emitters by physiological functions should be clarified for accurate dose verification. In this study, we visualized the distribution of irradiated radioactive beams, ¹¹C and ¹⁵O beams, in the rabbit whole-body using our original depth-of-interaction (DOI)-PET prototype to add basic data for biological washout effect correction. Time activity curves of the irradiated field and organs were measured immediately after the irradiations. All data were corrected for physical decay before further analysis. We also collected expired gas of the rabbit during beam irradiation and the energy spectrum was measured with a germanium detector. Irradiated radioactive beams into the brain were distributed to the whole body due to the biological washout process, and the implanted ¹¹C and ¹⁵O ions were concentrated in the regions which had high blood volume. The ¹¹C-labelled ¹¹CO₂ was detected in expired gas under the ¹¹C beam irradiation, while no significant signal was detected under the ¹⁵O beam irradiation as a form of C¹⁵O₂. Results suggested that the implanted ¹¹C ions form molecules that diffuse out to the whole body by undergoing perfusion, then, they are incorporated into the blood-gas exchange in the respiratory system. This study provides basic data for modelling of the biological washout effect.