LUNG TISSUE RESISTANCE IN HEALTHY CHILDREN

In ten healthy children, simultaneous measurements were made of the total pulmonary resistance and the airway resistance. The difference between these two measurements gave the lung tissue resistance which amounted to 1.08 ± 0.32 cm H2O/l/s (range, 0.65 to 1.59), or 29% of the total pulmonary resistance. It was on an average three times higher in children than in healthy adults. An inverse relation was found between lung tissue resistance and the vital capacity. Moreover, the results of measurements made in one child breathing at three different breathing patterns, indicate that with increasing tidal volume, lung tissue resistance increases. These observations suggest that lung tissue resistance itself is the sum of two components; one being due to the flow-dependent frictional forces of lung tissue, and the other, independent of flow resistance, being due to the nonideal elastic properties of the lung. The results obtained can be explained reasonably well on the basis of the latter component which seems to be much more important than the former. Speculation Dynamic measurements of the nonflow resistive hysteresis may give information about the properties of surface-active substance in healthy and diseased lungs. © International Pediatrics Research Foundation, Inc. 1968. All Rights Reserved.