Preoxygenation is a standard anesthetic technique for preventing hypoxemia during the induction of anesthesia. This is achieved by alveolar denitrogenation while ventilating the lungs with 100% oxy-gen. Until recently there was no satisfactory
nitrogen
monitoring device except mass spectrometry which is not generally available We used a convinient and readily available measuring technipue to evaluate the effectpreoxygenation. In 31 healthy volunteers breathing 100% oxygen, end-tidal oxygen
concentration have been measured at 15 seconds interval from the start of preoxygenation. A circle system was flushed with 100% oxygen and flow rate of 8 liter per minute. The gas sampling line of the Capnomac II (Datex, Finland) was placed in
nasal
cavity. At 1, 2, 3 minutes, mean end-tidal oxygen concentration was 78.7%, 89.2%, 91.9% respectively. End-tidal nitrogen concentration was approximately 16.1%, 5.8%, 3.2%. We conclude end-tidal oxygen concentration is a good indirect measure of
denitrogenation.
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