Performance of an active inspired hypoxic guard

摘要

Current hypoxic guards systems fail to maintain the inspired O-2 concentration (FIO2) a parts per thousand yen 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 O-2 Guard(A (R)), a smart hypoxic guard that increases O-2 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 O-2/air, the O-2 Guard(A (R)) was tested by administering O-2/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 O-2 Guard(A (R)) activation; (3) time from O-2 Guard(A (R)) activation to FIO2 = 25 ; (4) FGF and FDO2 used by the O-2 Guard. If SpO(2) was < 90 for 10 s or longer at any time, the patient was excluded. Three patients were excluded for low SpO(2). The incidence of FIO2 < 21 was 100 within the 1-2 L min(-1) FGF range. The O-2 Guard(A (R)) 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 O-2 Guard). FIO2 increased to 25 within 55 s after O-2 Guard activation in all patients. The O-2 Guard(A (R)), an active inspired hypoxic guard, rapidly reverses and limits the duration of inspired hypoxic episodes when the delivered hypoxic guard fails to do so.