caa a22 4500 605510229 CHVBK 20210128100644.0 cr unu---uuuuu 210128e20150801xx s 000 0 eng 10.1007/s10877-014-9626-y doi (NATIONALLICENCE)springer-10.1007/s10877-014-9626-y Hypoxic guard systems do not prevent rapid hypoxic inspired mixture formation [Elektronische Daten] [Sofie De Cooman, Caroline Schollaert, Jan Hendrickx, Philip Peyton, Tom Van Zundert, Andre De Wolf] Because a case report and theoretical mass balances suggested that hypoxic guard systems may not prevent the formation of hypoxic inspired mixtures (FIO2≤21%) over the clinically used fresh gas flow (FGF) range, we measured FIO2 over a wide range of hypoxic guard limits for O2/N2O and O2/air mixtures. After IRB approval, 16 ASA I-II patients received sevoflurane in either O2/N2O (n=8) or O2/air (n=8) using a Zeus® anesthesia machine in the conventional mode. After using an 8L/min FGF with FDO2=25% for 10min, the following hypoxic guard limits were tested for 4min each, expressed as [total FGF in L/min; FDO2 in %]: [0.3;85], [0.4;65], [0.5;50], [0.7;36], [0.85;30], [1.0;25], [1.25;25], [1.5;25], [2;25], [3;25], [5;25], and [8;25]. In between these [FGF;FDO2] combinations, 8L/min FGF with 25% O2 was used for 4min to return to the same baseline FIO2 (25%) before the start of the next combination. This sequence was studied once in each patient receiving O2/air (n=8), but twice in each patient who received O2/N2O (n=8) to examine the effect of decreasing N2O uptake over time, resulting in three groups: early O2/N2O, late O2/N2O, and O2/air group. The [FGF;FDO2]-FIO2 relationship was examined. The overall [FGF;FDO2]-FIO2 relationship in the three groups was similar. In all 1, 1.25, and 1.5L/min FGF groups, FIO2 decreased below 21% in all but one patient; this occurred within 1min in at least one patient. In the 0.7L/min O2/air group and the 3L/min late O2/N2O and O2/air groups, FIO2 decreased below 21% in one patient. Current hypoxic guard systems do not reliably prevent a hypoxic FIO2 with O2/N2O and O2/air mixtures, particularly between 0.7 and 3L/min. Springer Science+Business Media New York, 2014 Machine standards nationallicence Hypoxic guard system nationallicence Hypoxia nationallicence Hypoxic mixtures nationallicence Rebreathing nationallicence De Cooman Sofie Department of Anaesthesia, Kliniek Sint-Jan, Brussels, Belgium aut Schollaert Caroline Department of Anaesthesia, Intensive Care and Pain Therapy, OLV Hospital, Moorselbaan 164, 9300, Aalst, Belgium aut Hendrickx Jan Department of Anaesthesia, Intensive Care and Pain Therapy, OLV Hospital, Moorselbaan 164, 9300, Aalst, Belgium aut Peyton Philip Department of Anaesthesia, Austin Hospital, University of Melbourne, Parkville, Australia aut Van Zundert Tom Department of Anaesthesia, Intensive Care and Pain Therapy, OLV Hospital, Moorselbaan 164, 9300, Aalst, Belgium aut De Wolf Andre Department of Anaesthesia, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA aut Journal of Clinical Monitoring and Computing Springer Netherlands 29/4(2015-08-01), 491-497 1387-1307 29:4<491 2015 29 10877 https://doi.org/10.1007/s10877-014-9626-y text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10877-014-9626-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- De Cooman Sofie Department of Anaesthesia, Kliniek Sint-Jan, Brussels, Belgium aut NATIONALLICENCE 700 1- Schollaert Caroline Department of Anaesthesia, Intensive Care and Pain Therapy, OLV Hospital, Moorselbaan 164, 9300, Aalst, Belgium aut NATIONALLICENCE 700 1- Hendrickx Jan Department of Anaesthesia, Intensive Care and Pain Therapy, OLV Hospital, Moorselbaan 164, 9300, Aalst, Belgium aut NATIONALLICENCE 700 1- Peyton Philip Department of Anaesthesia, Austin Hospital, University of Melbourne, Parkville, Australia aut NATIONALLICENCE 700 1- Van Zundert Tom Department of Anaesthesia, Intensive Care and Pain Therapy, OLV Hospital, Moorselbaan 164, 9300, Aalst, Belgium aut NATIONALLICENCE 700 1- De Wolf Andre Department of Anaesthesia, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA aut NATIONALLICENCE 773 0- Journal of Clinical Monitoring and Computing Springer Netherlands 29/4(2015-08-01), 491-497 1387-1307 29:4<491 2015 29 10877