Nicholas Gant1,2, Hanna van Waart3, Edward T Ashworth1, Peter Mesley4, Simon J Mitchell3,5. 1. Department of Exercise Sciences, University of Auckland, New Zealand. 2. Corresponding author: Department of Exercise Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand, n.gant@auckland.ac.nz. 3. Department of Anaesthesiology, University of Auckland, New Zealand. 4. Lust4Rust Diving Excursions, Auckland, New Zealand. 5. Department of Anaesthesia, Auckland City Hospital, Auckland, New Zealand.
Abstract
INTRODUCTION: Scrubbers in closed-circuit rebreather systems remove carbon dioxide (CO2) from the exhaled gas. In an attempt to be more user-friendly and efficient, the ExtendAir® non-granular, pre-formed scrubber cartridge has been developed. The cartridge manufacturer claims twice the absorptive capacity of granular CO2 absorbent, with less variability, lower work of breathing, and reduced exposure to caustic chemicals after a flood. To our knowledge there are no published data that support these claims. METHODS: Cartridge (ExtendAir®) and granular (Sofnolime® 797) scrubbers of equal volume and mass were tested five times in an immersed and mechanically ventilated O2ptima rebreather. Exercise protocols involving staged (90 minutes 6 MET, followed by 2 MET) and continuous (6 MET) activity were simulated. We compared: duration until breakthrough, and variability in duration, to endpoints of 1.0 kPa and 0.5 kPa inspired partial pressure of CO2; inspiratory-expiratory pressure difference in the breathing loop; and pH of eluted water after a 5 minute flood. RESULTS: Mean difference in scrubber endurance was 0-20% in favour of the ExtendAir® cartridge, depending on exercise protocol and chosen CO2 endpoint. There were no meaningful differences in endpoint variability, inspiratory-expiratory pressure in the loop, or pH in the eluted water after a flood. CONCLUSIONS: Cartridge and granular scrubbers were very similar in duration, variability, ventilation pressures, and causticity after a flood. Our findings were not consistent with claims of substantial superiority for the ExtendAir® cartridge. Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.
INTRODUCTION: Scrubbers in closed-circuit rebreather systems remove carbon dioxide (CO2) from the exhaled gas. In an attempt to be more user-friendly and efficient, the ExtendAir® non-granular, pre-formed scrubber cartridge has been developed. The cartridge manufacturer claims twice the absorptive capacity of granular CO2 absorbent, with less variability, lower work of breathing, and reduced exposure to caustic chemicals after a flood. To our knowledge there are no published data that support these claims. METHODS: Cartridge (ExtendAir®) and granular (Sofnolime® 797) scrubbers of equal volume and mass were tested five times in an immersed and mechanically ventilated O2ptima rebreather. Exercise protocols involving staged (90 minutes 6 MET, followed by 2 MET) and continuous (6 MET) activity were simulated. We compared: duration until breakthrough, and variability in duration, to endpoints of 1.0 kPa and 0.5 kPa inspired partial pressure of CO2; inspiratory-expiratory pressure difference in the breathing loop; and pH of eluted water after a 5 minute flood. RESULTS: Mean difference in scrubber endurance was 0-20% in favour of the ExtendAir® cartridge, depending on exercise protocol and chosen CO2 endpoint. There were no meaningful differences in endpoint variability, inspiratory-expiratory pressure in the loop, or pH in the eluted water after a flood. CONCLUSIONS: Cartridge and granular scrubbers were very similar in duration, variability, ventilation pressures, and causticity after a flood. Our findings were not consistent with claims of substantial superiority for the ExtendAir® cartridge. Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.
Authors: Carolyn Deng; Neal W Pollock; Nicholas Gant; Jacqueline A Hannam; Adam Dooley; Peter Mesley; Simon J Mitchell Journal: Diving Hyperb Med Date: 2015-03 Impact factor: 0.887
Authors: David Harvey; Neal W Pollock; Nicholas Gant; Jason Hart; Peter Mesley; Simon J Mitchell Journal: Diving Hyperb Med Date: 2016-06 Impact factor: 0.887