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> I'm in over my head!!! Jason is essentially right. I remember the case he mentioned from J.L.'s book, and if it is the same incident, know those involved. N2O (that is what is in the whipped cream can) is a highly diffusible gas. This is why N2O can cause dilutional hypoxia in anaesthesia once it is switched off, just like He can during decompression. Where a volunteer rat has pre-existing air bubbles, and is made to breath N2O, the bubbles grow more rapidly than with air or O2 breathing. This is confirmed experimentally by direct visualisation of air bubbles created by decompression or injection (Hyldegaard, O., Moller, M. and Madsen, J. (1991) Effect of He-O2, O2, and N2O-O2 breathing on injected bubbles in spinal white matter. Undersea Biomed. Res. 18, 361-371.; Hyldegaard, O. and Madsen, J. (1989) Influence of heliox, oxygen, and N2O-O2 breathing on N2 bubbles in adipose tissue. Undersea Biomed. Res. 16, 185-193.) It is quite likely that air bubbles become stabilised by coating with surface active molecules (surfactants) and persist in the body for many days or weeks. The case that Jason cited suggests that these bubbles can persist for up to 4 weeks, since this diver developed DCI from N2O inhalation 4 weeks after the last dive (as an aside, I have a vague recollection that there was some uncertainty about the interval between last dive and anaesthetic). IN experimental work N2O breathing only enlarged visible bubbles, once bubbles had shrunk beyond a size detectable by the microscope used in the study, they could not be reactivated. regards, David Doolette ddoolett@me*.ad*.ed*.au*
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