![]() ![]() 4Duke-NUS Medical School, Singapore, Singaporeīackground: Alveolar dead-space fraction (AVDSF), the volume of alveolar gas that does not participate in gas exchange, has been reported to predict mortality and morbidity in adults with acute respiratory distress syndrome (ARDS).3Center for Quantitative Medicine, Duke-NUS Medical School, Singapore, Singapore.2Children's Intensive Care Unit, Department of Pediatric Subspecialties, KK Women's and Children's Hospital, Singapore, Singapore.1Lee Kong Chian School of Medicine, Singapore, Singapore.All rights reserved.Sheow Boon Oh 1 Apollo Aguilan 2 Herng Lee Tan 2 Yi-Jyun Ma 2 Rehena Sultana 3 Jan Hau Lee 2,4 Judith Ju Ming Wong 1,4 * Published by Oxford University Press on behalf of the British Journal of Anaesthesia. CO₂ reflection from the ACD limits its use with low tidal volume ventilation, such as with lung protection ventilation strategies.Īirway anaesthetic techniques carbon dioxide dead space inhalation rebreathing. Our calculations show that with the use of the ACD, normocapnia cannot be achieved with tidal volume <6 ml kg(-1) even when respiratory rate is increased.Īn ACD causes a dead space effect larger than its internal volume due to reflection of CO₂, which is attenuated but not abolished by sevoflurane administration. In patients, the mean dead space effect with 0.8% sevoflurane was 88 ml larger using the ACD compared with the HME (P<0.001), of which 38 ml was due to CO₂ reflection. Sevoflurane reduced but did not abolish CO₂ reflection. Reflection of CO₂ and dead space effects were evaluated with the single-breath test for CO2. ![]() The ACD was also studied with a test lung at high sevoflurane concentrations. Twelve postoperative patients received mechanical ventilation using a conventional heat and moisture exchanger (HME, internal volume 50 ml) and an ACD (100 ml), the latter with or without administration of sevoflurane. An analysis of clinical implications of our findings was performed. This study tests the hypothesis that sevoflurane further attenuates reflection of CO₂. CO₂ reflection from the ACD is attenuated by humidity. Expired CO₂ is, however, also reflected causing a dead space effect in excess of the ACD internal volume. The anaesthetic conserving device AnaConDa (ACD) reflects exhaled anaesthetic agents thereby facilitating the use of inhaled anaesthetic agents outside operating theatres. ![]()
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