Neal W Pollock1,2, Nicholas Gant3, David Harvey4, Peter Mesley5, Jason Hart3, Simon J Mitchell4,6. 1. Department of Kinesiology, Université Laval, Quebec, Canada. 2. Service de Médecine Hyperbare, Centre de Médecine de Plongée du Québec, Hôtel-Dieu de Lévis, Levis, Quebec. 3. Exercise Neurometabolism Laboratory, Department of Exercise Science, University of Auckland, Auckland, New Zealand. 4. Department of Anaesthesia, Auckland City Hospital, Auckland. 5. Lust for Rust Diving, Auckland. 6. Corresponding author: Department of Anaesthesiology, School of Medicine, University of Auckland, Private Bag 92019, Auckland, New Zealand. sj.mitchell@auckland.ac.nz.
Abstract
INTRODUCTION: Diving rebreathers use "scrubber" canisters containing soda lime to remove carbon dioxide (CO2) from the expired gas. Soda lime has a finite ability to absorb CO2. We undertook an experiment to determine whether the manner of storage of a partly used scrubber affected subsequent CO2 absorption. METHODS: An Evolution Plus™ rebreather was mechanically ventilated in a benchtop circuit. Respiratory minute volume was 45 L·min-1 and CO2 was introduced to the expiratory limb at 2 L·min-1. The scrubber canister was packed with 2.64 kg of Sofnolime 797™. Scrubbers were run in this circuit for 90 minutes then removed from the rebreather and stored in packed form under one of three conditions: "open" (unsealed) for 28 days (n = 4); vacuum "sealed" in an airtight plastic bag for 28 days (n = 5); or open overnight (n = 5). Following storage the scrubber canisters were placed back in the rebreather and run as above until the PCO2 in the inspired gas exceeded 1 kPa. The total duration of operation to reach this end-point in each storage condition was compared. RESULTS: The mean run times to reach an inspired CO2 of 1 kPa were 188, 241, and 239 minutes in the open-28-day, the sealed-28-day and the open-overnight storage conditions, respectively. CONCLUSION: Rebreather divers should consider placing partially used soda lime scrubber canisters in vacuum-sealed plastic bags if storing them for longer periods than overnight. If a partially used scrubber canister is to be used again the next day then the storage modality is unlikely to influence scrubber efficacy. 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: Diving rebreathers use "scrubber" canisters containing soda lime to remove carbon dioxide (CO2) from the expired gas. Soda lime has a finite ability to absorb CO2. We undertook an experiment to determine whether the manner of storage of a partly used scrubber affected subsequent CO2 absorption. METHODS: An Evolution Plus™ rebreather was mechanically ventilated in a benchtop circuit. Respiratory minute volume was 45 L·min-1 and CO2 was introduced to the expiratory limb at 2 L·min-1. The scrubber canister was packed with 2.64 kg of Sofnolime 797™. Scrubbers were run in this circuit for 90 minutes then removed from the rebreather and stored in packed form under one of three conditions: "open" (unsealed) for 28 days (n = 4); vacuum "sealed" in an airtight plastic bag for 28 days (n = 5); or open overnight (n = 5). Following storage the scrubber canisters were placed back in the rebreather and run as above until the PCO2 in the inspired gas exceeded 1 kPa. The total duration of operation to reach this end-point in each storage condition was compared. RESULTS: The mean run times to reach an inspired CO2 of 1 kPa were 188, 241, and 239 minutes in the open-28-day, the sealed-28-day and the open-overnight storage conditions, respectively. CONCLUSION: Rebreather divers should consider placing partially used soda lime scrubber canisters in vacuum-sealed plastic bags if storing them for longer periods than overnight. If a partially used scrubber canister is to be used again the next day then the storage modality is unlikely to influence scrubber efficacy. 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.
Entities:
Keywords:
Equipment; Hypercapnia; Respiratory; Soda lime; Technical diving
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