Diffusion hypoxia is seen with -

DIFFUSION HYPOXIA also known as FINK EFFECT OR THIRD GAS EFFECT At the end of general anesthesia, N2O is switched off so that inspired gas changes from N2O+O2 - N2+O2. As a result, N2O stas diffusing out of the blood into alveoli while N2 diffuses into blood. Due to the difference in solubilities of the two gases, N2O diffuses out more rapidly as it has high solubility. This diluted other gases present in alveoli and relative concentration of O2 falls. It is termed as diffusion hypoxia. Clinical Significance : 100% oxygen should be given for at least 5-10minutes after switching off N2O in order to overcome the relative fall of O2 concentration in the alveoli during Recovery from general anesthesia.