Influence of the reference gas or paramagnetic oxygen analyzers on nitrogen concentrations during closed-circuit anesthesia

Jan F A Hendrickx, Andre A J Van Zundert, Andre M. De Wolf*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Nitrogen (N2) may accumulate to unacceptable levels during closed-circuit anesthesia (CCA) when the sampled gases are redirected to the anesthesia circuit, because many gas analyzers entrain air as a reference gas to calibrate for oxygen analysis. Using oxygen instead of air as the reference gas for paramagnetic oxygen analysis could attenuate N2 accumulation. Forty-three adult ASA physical status I-III patients undergoing a variety of peripheral and abdominal procedures were assigned to one of two groups, depending on the reference gas used by a paramagnetic oxygen analyzer, either air (group I, n = 23) or oxygen (group II, n = 20). Gases sampled by the multigas analyzer were redirected to the anesthesia circuit. End-expired N2 (N(2 Et)) was calculated as 'balance gas': (100 - %O2 - %anesthetic vapor - %CO2). N(2 Et) after 55 min (N(2 Et 55 min)) was correlated with the end-expired N2 concentration when the circuit was closed (N(2 Et 0 min)) and 5 min (N(2 Et 5 min)) thereafter. In group I, N(2 Et) accumulated almost linearly over time (t, min): N(2 Et) (%) = 2.47 + 0.61 * t (r2 = 0.999). N(2 Et 0 min), N(2 Et 5 min), and N(2 Et 55 min) were 1.3 ± 0.8, 5.3 ± 1.7, and 35.3 ± 5.3%, respectively (mean ± SD). The correlation (r2) between N(2 Et 55 min) and N(2 Et 0 min) was 0.19, and between N(2 Et 55 min) and N(2 Et 5 min) it was 0.56. In group II, N(2 Et) increased exponentially: N(2 Et) (%) = 1.01 + 11.9 * (1 - e(-t/43.5)) (r2 = 0.99). N(2 Et 0 min), N(2 Et 5 min), and N(2 Et 55 min) were 0.87 ± 0.93, 2.6 ± 1.5, and 10.1 ± 2.9%, respectively. The correlation (r2) between N(2 Et 55 min) and N(2 Et 0 min) was 0.04, and between N(2 Et 55 min) and N(2 Et 5 min) it was 0.40. We conclude that paramagnetic oxygen analyzers that use oxygen as the reference gas significantly attenuate N2 accumulation during CCA, which may reduce the need for frequent flushing of the anesthesia system, may provide more constant oxygen and nitrous oxide concentrations, and may simplify pharmacokinetic studies of potent inhaled anesthetics.

Original languageEnglish (US)
Pages (from-to)381-384
Number of pages4
JournalJournal of Clinical Monitoring and Computing
Volume14
Issue number6
DOIs
StatePublished - Aug 1 1998

Keywords

  • Closed-circuit anesthesia
  • Equipment
  • Multigas analyzer
  • Nitrogen accumulation
  • Oxygen analyzer

ASJC Scopus subject areas

  • Health Informatics
  • Critical Care and Intensive Care Medicine
  • Anesthesiology and Pain Medicine

Fingerprint Dive into the research topics of 'Influence of the reference gas or paramagnetic oxygen analyzers on nitrogen concentrations during closed-circuit anesthesia'. Together they form a unique fingerprint.

Cite this