Evaluation of accuracy, filter performance, and durability among capnography sampling lines: a bench study

The aim of this bench study was to assess performance between currently available sidestream capnography sampling lines claiming compatibility with a Microstream™ enabled monitor system. A series of bench tests were performed on a selection of commercially available sampling lines (oral-nasal cannulas, PetCO2 masks, and procedural bite blocks) to assess PetCO2 accuracy, filter performance and mechanical durability. For each testing procedure, three separate sampling lines were assessed for five repetitions (n = 15 for each product). A 3D printed oral-nasal model connected to a lung simulator was set to two different breathing modes to simulate “normal” and “shallow” breathing. PetCO2 accuracy measurements were completed at both breathing modes to simulate a variety of clinical scenarios, including oxygen delivery. Filter performance and mechanical durability were assessed for cannula sampling lines. When evaluating PetCO2 accuracy across all sampling line types and breathing conditions, error estimates were lowest for matched-paired sampling lines, compared to cross-paired sampling lines. For oral-nasal cannulas, the matched-paired and three cross-paired performed within the system specification for “normal” breathing conditions. Split design oral-nasal cannulas consistently fell outside specifications under conditions of nasal obstruction. Five cross-paired filters clogged prior to expected threshold, with four demonstrating a clog capacity of less than half the expected value. Almost all sampling lines passed mechanical durability testing. Across all testing conditions, cross-paired sampling lines were observed to fall outside system specifications, suggesting that using sampling lines outside the Microstream™ family may disrupt accuracy of readings when using a Microstream™ enabled capnography monitor.