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Reducing the oxygen concentration of gases delivered from anaesthetic machines unadapted for medical air
  1. R. E. Clutton, BVSc, MRCVS, DVA, DiplECVAA, MRCA1,
  2. G. Schoeffmann, DrVetMed1,
  3. M. Chesnil, DrVetMed1,
  4. R. Gregson, BVM&S, MRCVS1,
  5. F. Reed, BVSc, MRCVS1,
  6. H. Lawson, MSc1 and
  7. M. Eddleston, MD, PhD2
  1. Department of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, Easter Bush, Roslin, Midlothian, EH25 9RG, UK
  2. Clinical Pharmacology Unit, Centre for Cardiovascular Science, University of Edinburgh and National Poisons Information Service Edinburgh, Royal Infirmary of Edinburgh, Edinburgh, UK
  1. E-mail for correspondence e.clutton{at}

High fractional concentrations of inspired oxygen (FiO2) delivered over prolonged periods produce characteristic histological changes in the lungs and airway of exposed animals. Modern medical anaesthetic machines are adapted to deliver medical air (FiO2=0.21) for the purpose of reducing FiO2; anaesthetic machines designed for the veterinary market have not been so adapted. Two inexpensive modifications that allow medical air to be added to the gas flow from veterinary anaesthetic machines are described. The advantages and disadvantages of each modification are discussed.

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  • Provenance not commissioned; externally peer reviewed

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