title: Failure of the Kety-Schmidt nitrous oxide method for determination of myocardial blood flow.
abstract: 1. The reliability of the Kety-Schmidt nitrous oxide (N2O) blood-tissue equilibration method was examined in 50 studies of myocardial blood flow in seven conscious, unrestrained sheep using a newly developed carefully validated gas chromatographic assay for N2O. 2. In 10 studies the arterial and coronary sinus N2O blood concentration-time curves converged as expected at the end of the 10 min sampling period. In 14 studies they crossed over, and in 26 studies, the curves failed to converge. 3. A survey of the literature revealed that such results have been encountered previously but have not been accorded particular significance. An ultimate matching equilibrium between arterial and venous blood N2O concentration-time curves is, however, fundamental to the validity of the method. 4. The results indicate that the use of the Kety-Schmidt method with N2O as the indicator gas is invalid as applied to the measurement of myocardial blood flow in this preparation.
authors.affiliation: Department of Anaesthesia and Intensive Care, Flinders Medical Centre, Flinders University of South Australia, Adelaide.
authors.forename: M A
authors.initials: MA
authors.lastname: Reid
authors.forename: L E
authors.initials: LE
authors.lastname: Mather
authors.forename: W B
authors.initials: WB
authors.lastname: Runciman
authors.forename: C F
authors.initials: CF
authors.lastname: McLean
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002404:Catheterization; D002849:Chromatography, Gas; D003326:Coronary Circulation / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D009609:Nitrous Oxide / Q000097:blood; D012756:Sheep
chemical_list: D009609:Nitrous Oxide