title: A comparison of direct and indirect measurements of oxygen delivery and consumption: the effects of prostacyclin in two human volunteers.
abstract: To examine the relation of oxygen delivery to uptake in normals, we have measured cardiac index, oxygen delivery and oxygen consumption directly and indirectly in two human volunteers before and during a prostacyclin (PGI2) infusion (5 ng/kg/min). We have also investigated the relation of direct and indirect measurements of delivery to consumption in two critically ill patients over a more prolonged study period of 24 hours. Overall, there were close correlations between both cardiac index measured by thermodilution with that calculated from the Fick equation (r = 0.97 p less than 0.001) and oxygen consumption measured directly by analysis of inspired gases (V O2) with that calculated by the reverse Fick method (OUI) (r = 0.95 p less than 0.001). Nevertheless, the limits of agreement between the two methods were wide (1.6 L/min.m2 for the cardiac index and 70.5 ml 02/min.m2 for oxygen consumption, 95% confidence limits). In the two human volunteers, PGI2 produced substantial increases in oxygen delivery but there was no change in oxygen consumption measured directly or indirectly; V O2 and OUI were unrelated and independent of oxygen delivery. However, in the two patients studied over 24 hours, there were close correlations between delivery and both V O2 (r = 0.93 p less than 0.001) and OUI (r = 0.94 p less than 0.001). These results suggest that the derivation of oxygen consumption by the reverse Fick method (OUI) is a reasonable substitute for direct measurements of V O2 but occasionally the absolute values so obtained may be somewhat different.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine and Intensive Therapy, Middlesex Hospital, London.
authors.forename: D J
authors.initials: DJ
authors.lastname: Bihari
authors.forename: M
authors.initials: M
authors.lastname: Smithies
authors.forename: A
authors.initials: A
authors.lastname: Pozniak
authors.forename: A
authors.initials: A
authors.lastname: Gimson
mesh_terms: D000328:Adult; D001784:Blood Gas Analysis; D001794:Blood Pressure; D011464:Epoprostenol / Q000494:pharmacology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D010100:Oxygen / Q000502:physiology*; D010101:Oxygen Consumption / Q000187:drug effects*
chemical_list: D011464:Epoprostenol; D010100:Oxygen