Comparison of four methods for measuring mammary blood flow in conscious goats

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Abstract
Three methods for measuring mammary blood flow, the ^O-diffusion (N2O), continuous-thermodilution (CT), and antipyrine-absorption (AP) method, were compared simultaneously in anesthetized and conscious lactating goats. After establishing the reliability of a 4th method, the electromagnetic (EM) method, for measuring mammary arterial flow, it was used to check procedures and to compare its results with those of the 1st 3 methods. EM monitoring showed that no procedures interfered with measurement of normal mammary blood flow. The CT method gave values close to those of EM, averaging within 6% of EM in 36 comparisons. The N2O method gave results similar to EM in 5 of 6 acute experiments, but averaged 19% lower than CT values in 18 conscious animals. The AP method overestimated flow in both anesthetized and conscious goats, averaging 30% greater than CT results in 17 conscious experiments. Reasons for differences between CT and EM, N2O and CT, and AP and CT values are discussed. Advantages and disadvantages of each method are summarized.