title: Pre-oxygenation in pregnancy: an investigation using physiological modelling.
abstract: Hypoxaemia during anaesthetic induction in obstetrics is hazardous for mother and baby, but the onset of desaturation can be delayed by pre-oxygenation. This study investigated pre-oxygenation during pregnancy using computer simulation. The Nottingham Physiology Simulator was configured to replicate normal pregnant physiology. Three pregnant and three non-pregnant subjects were created, representing population variation according to published physiological values. They underwent pre-oxygenation by tidal and vital capacity breathing of 100% oxygen. Pre-oxygenation during tidal breathing proceeded more rapidly in pregnancy, the median [range] time to achieve 95% of the maximum change in P(E)O2 being 1 min 37 s [1:23-1:52] in pregnant subjects, compared to 2 min 51 s [2:28-3:15] in non-pregnant subjects. Vital capacity pre-oxygenation required seven breaths [5-10] in pregnant subjects, compared to six breaths [4-9] in non-pregnant subjects, to achieve the same P(E)O2 as after 95% complete tidal pre-oxygenation. We recommend 2 min of tidal breathing for pre-oxygenation in pregnancy.
authors.affiliation: Queen's Medical Centre campus, Nottingham University Hospitals NHS Trust, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: S H
authors.initials: SH
authors.lastname: McClelland
authors.forename: D G
authors.initials: DG
authors.lastname: Bogod
authors.forename: J G
authors.initials: JG
authors.lastname: Hardman
mesh_terms: D000768:Anesthesia, General; D000773:Anesthesia, Obstetrical; D002585:Cesarean Section; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008954:Models, Biological; D010100:Oxygen / Q000097:blood*; D010102:Oxygen Inhalation Therapy; D010313:Partial Pressure; D011247:Pregnancy / Q000097:blood / Q000502:physiology*; D011300:Preoperative Care / Q000379:methods; D015656:Respiratory Mechanics
chemical_list: D010100:Oxygen