Velocity profiles in the main pulmonary artery of dogs and man, measured with a thin-film resistance anemometer.

Instantaneous velocity of pulmonary artery blood was measured using a thin-film resistance anemometer mounted on a hypodermic needle. Studies were performed, at thoracotomy, in five dogs and five patients. Instantaneous blood velocity was recorded at several sites across die transverse axis of the main pulmonary artery to determine the shape of the velocity profile. We found the velocity profile, in both man and dog, to be approximately flat. In dog, the mean velocity, normalized to that at the center line, ranged from 1.18 (S D ± 0. 0 3) to 0.81 (S D ± 0. 2 7). In man, mean velocity of pulmonary artery blood, normalized in a similar fashion, ranged from 1.08 (SD ± 0.03) to 0.84 (S D ± 0.07), while the normalized peak systolic velocity ranged from 1.04 (S D ± 0. 0 7) to 0.95 (S D ± 0. 1 6). The results, in dogs, suggest that there is little asymmetry of the velocity profile and therefore these have been taken as evidence that the use of cuff electromagnetic flowmeters on the pulmonary artery of dogs is not subject to significant inaccuracies associated with a nonsymmetrical flow profile. The finding of a relatively flat velocity profile in patients, moreover, will make it easier for catheter-tip flowmeters to measure bulk velocity in the pulmonary artery. ADDITIONAL KEY WORDS axi-symmetrical Fourier analysis electromagnetic impedance pulmonary hypertension • Recently Schultz and his colleagues (1) described a thin-film resistance anemometer designed to measure instantaneous fluid velocity. The thin-film bead, when mounted on a hypodermic needle, was used by these workers to map the distribution of blood velocity across the transverse axis of the aorta in both dogs and man. They subsequently extended their work by measuring the velocity of aortic blood flow with a catheter-tip, thin-film resistance anemometer during routine cardiac catheterization. The results of this work have been reported in greater detail by Tunstall Pedoe (2). Several groups of workers have stressed the need for caution in the interpretation of flow measurements using cuff electromagnetic flowmeters. Wyatt (3), Goldman (4) and Bergel and Gessner (5) have particularly emphasized the need for the blood flow in a vessel to have an axi-symmetrical velocity profile, before the volume flow rate in that vessel can be related to the output of the electromagnetic flowmeter. However, at present the shape of the velocity profile in the pulmonary artery is not known. This knowledge …