title: Performance of an active inspired hypoxic guard.
abstract: Current hypoxic guards systems fail to maintain the inspired O2 concentration (FIO2) ≥ 21 % across the entire fresh gas flow (FGF) range when a second carrier gas is used (N2O or air). We examined the performance of the Maquet O2 Guard(®), a smart hypoxic guard that increases O2 delivery if an inspired hypoxic mixture is formed. After obtaining IRB approval and informed consent, 12 ASA I-II patients were enrolled. During anesthesia with sevoflurane in O2/air, the O2 Guard(®) was tested by administering O2/air at the following delivered hypoxic guard limits [expressed as (total FGF in L min(-1); FDO2 in %)] for 4 min each: [0.3;67], [0.4;50], [0.6;34], [0.8;25], [1.0;21], [1.2;21], [1.5;21], [2;21], [3;21], and [5;21]. The following data were collected: (1) time from FIO2 = 30 to 20 %; (2) time from FIO2 = 20 % to O2 Guard(®) activation; (3) time from O2 Guard(®) activation to FIO2 = 25 %; (4) FGF and FDO2 used by the O2 Guard. If SpO2 was <90 % for 10 s or longer at any time, the patient was excluded. Three patients were excluded for low SpO2. The incidence of FIO2 < 21 % was 100 % within the 1-2 L min(-1) FGF range. The O2 Guard(®) was activated within 20 s after FIO2 became 20 %, except in one patient where FIO2 oscillated between 20 and 21 %. FDO2 was increased to 60 % and FGF to 1 L min(-1) (the latter only if it was lower than 1 L min(-1) prior to activation of the O2 Guard). FIO2 increased to 25 % within 55 s after O2 Guard activation in all patients. The O2 Guard(®), an active inspired hypoxic guard, rapidly reverses and limits the duration of inspired hypoxic episodes when the delivered hypoxic guard fails to do so.
authors.affiliation: Department of Anesthesiology, Intensive Care and Pain Therapy, OLV Hospital, Aalst, Belgium.
authors.forename: Idris E
authors.initials: IE
authors.lastname: Ghijselings
authors.affiliation: Department of Anesthesiology, Sint-Jan Clinic, Brussels, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: De Cooman
authors.affiliation: Department of Anesthesiology, Intensive Care and Pain Therapy, OLV Hospital, Aalst, Belgium.
authors.forename: Rik
authors.initials: R
authors.lastname: Carette
authors.affiliation: Department of Anesthesia, Austin Hospital and University of Melbourne, Melbourne, Australia.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Peyton
authors.affiliation: Department of Anesthesiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: Andre M
authors.initials: AM
authors.lastname: De Wolf
authors.affiliation: Department of Anesthesiology, Intensive Care and Pain Therapy, OLV Hospital, Aalst, Belgium. jcnwahendrickx@yahoo.com.
authors.forename: Jan F A
authors.initials: JF
authors.lastname: Hendrickx
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000769:Anesthesia, Inhalation / Q000295:instrumentation* / Q000379:methods; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D056902:Clinical Alarms; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods; D009609:Nitrous Oxide / Q000008:administration & dosage* / Q000032:analysis; D010100:Oxygen / Q000008:administration & dosage*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D018685:Anesthetics, Inhalation; D009609:Nitrous Oxide; D010100:Oxygen
keywords: Hypoxia; Hypoxic guard system; Hypoxic mixtures; Machine standards