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Abstract
Introduction The Diamedica Draw-over Vaporiser 2 (DDV2) is the sevoflurane vaporiser used by the UK Defence Medical Services to provide deployed volatile general anaesthesia. The Defence Anaesthesia System employs the DDV2 with a turbine-driven ventilator as a ‘push-over’ vaporiser, a modification from the manufacturer’s design. We investigated sevoflurane delivery at varying minute volumes (MVs), vaporiser settings and temperatures in this configuration.
Methods A range of DDV2 settings (1%, 2%, 3%, 4% and induction) and MVs (2, 4, 6 and 8 L/min at 12 ventilations per minute) were tested at two ambient temperatures (20 and 30±3°C) over 30 min. A supplemental experiment, simulating anaesthesia during damage control surgery, was also completed, where he DDV2 was set to 2% with a 6 L/min MV for 90 min.
Results In both experiments, two distinct phases of sevoflurane delivery were noted, a ‘wash-in phase’ followed by a ‘maintenance period’. The wash-in phase normally lasted less than 5 min. During the maintenance period at low MVs and vaporiser settings the DDV2 delivered a constant output, while at higher MVs and settings vapour output fell predictably. At 20±3°C, using DDV2 settings likely to be encountered in clinical practice, sevoflurane delivery was within 20% of that set. Higher vaporiser settings, MVs and temperatures resulted in greater variation between vaporiser setting and agent delivery. This variation is explained by the incomplete temperature compensation of the DDV2.
Conclusions The DDV2 functions predictably at a range of settings, MVs and temperatures. Anaesthetic delivery in the defence anaesthesia configuration is like that previously described in the draw-over configuration. The equipment was found to be reliable and robust. This experimental work supports the continued use of the Defence Anaesthesia System for the delivery of and training in deployed general anaesthesia.
- ANAESTHETICS
- Adult anaesthesia
- Paediatric anaesthesia
Data availability statement
Data are available upon reasonable request.
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Data availability statement
Data are available upon reasonable request.
Footnotes
Contributors SB: overall content guarantor, experimental conduct, reporting, data acquisition, analysis and interpretation, write-up lead. OR: experimental conduct, reporting, data acquisition, analysis and interpretation, write-up. TF: experimental lead, conduct, reporting and design, acquisition of data, write-up. DC: planning, conception and design.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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