Ischemia in a hollow internal organ can be detected in its incipient stages by obtaining a CO.sub.2 sample from within the organ of interest, measuring the partial pressure of CO.sub.2 sample, measuring the bicarbonate concentration of an arterial blood sample, and on the basis of these two measurements...http://www.google.es/patents/US5526809?utm_source=gb-gplus-sharePatente US5526809 - Hollow viscous and soild organ tonometry
