| Abstract: | After a single inhalation of C15O2 labelled air, from residual volume to total lung capacity, followed by a few seconds apnea, it is possible to record in four or six lung zones the regional activity changes on a time basis. A first fast rise in activity is seen during the inhalation phase, corresponding to the ventilation in the region of interest (ROI). During the apnea, a slower decreasing component is observed in the different ROI, proportional to the regional blood flow, as almost instantaneously C15O2 is converted to labelled water. After the pioneer work of West & Dollery (1962) very few papers appeared on the subject despite technical improvements as, for instance, coincidence counting of radioactive events. We thus decided to improve the reproducibility and accuracy of the method which were of such a poor quality that no individual measurements were possible in the past. Were of critical importance: a careful positioning of the patients between the counters, a faster electronics improving true coincidence counting. In six healthy volunteers (age 22-35) the values obtained for regional ventilation with the C15O2 single breath were compared to the values given by the inhalation of a poorly soluble gas (Nitrogen13). The correlation between the two sets of measurements is high (r = 0.975). The slope of the regression line is 0.859, ordinate at origin is 2.35. This reveals a systematic error. A mathematical model was therefore developed to take into account the "washout" occurring during the constitution of the ventilation peak, and to correct its value.(ABSTRACT TRUNCATED AT 250 WORDS) |
