Cardiogenic oscillations as an index of pulmonary blood flow distribution’

index of pulmonary blood_flow distribution. J. Appl. Physiol. 18(2): 233-243. I g63.A relationship has been developed between the amplitudes of cardiogenic oscillations of expired gas ten-sions and the ratio of blood flows through upper and lower zones of the erect human lung. Instrumental methods have been devised for the accurate measurement of the amplitudes of these oscillations. A theoretical and experimental study was made of the sources of error. The ratio of upper- to lower-zone blood flow could be determined with a reproducibility of =t20 % so that changes in this ratio of greater than 2oQjg, at-tendant upon a stimulus, could be identified. C ARDIAC-INDUCED OSCILLATIONS in the expired gas tensions of normal subjects have been reported by several workers. A good example of such oscillations is shown in the mass spectrometer record in Fig. I. In