DISTRIBUTION OF PULMONARY VENTILATION AND PERFUSION MEASURED SIMULTANEOUSLY IN AWAKE GOATS

Gravity has been regarded as the major determinant for local pulmonary perfusion and ventilation. Recent reports, describing major gravity-i ndependent heterogeneity in both variables, have questioned the import ance of gravity. We asked to what extent ventilation and perfusion wer e related, and if they showed similar distributions along the vertical axis in the lung. We gave Tc-99m-aerosols as tracers for ventilation and radioactive microspheres as blood flow tracers in five awake goats over 4 min. Ventilation and perfusion were determined in similar to 1 .5 cm(3) pieces of the lung. For both variables the vertical distribut ion could vary considerably from lung to lung. but within each lung th e two distributions were similar. Both ventilation and perfusion were heterogeneously distributed (CV similar to 40% for both), they were hi ghly correlated (r = 0.81) and the average 25-75-interpercentile inter val for ventilation to perfusion ratio (0.84-2.13) was significantly l ess wide than for both ventilation (0.76-1.38) and perfusion (0.76-1.4 0). Some pieces were considerably overventilated while few were corres pondingly underventilated. This could indicate that perfusion is adjus ted to ventilation in normoxic lungs with a low sensitivity to overven tilation.