Fig. 1.

Changes in transmural absorbance spectra, and the underlying chromophores, when left ventricular working hearts were transitioned from Krebs-Henseleit (KH) to perfluorocarbon (PFC) perfusate. A: changes in myoglobin (red line), cytochrome (Cyt) c (green line), and cytochrome a₆₀₅ (blue line) from a representative experiment when the perfusate was transitioned from KH to PFC at minute 0. Upon the transition, the oxygen saturation of myoglobin increased, as indicated by an increase in the fitted change in spectral optical density (ΔOD^*) for myoglobin. Cytochromes a₆₀₅ and c were oxidized, indicated by a decrease in ΔOD^*. Values represent averages of n = 11 ± SE. *Significantly different from baseline. B: representative KH to PFC absorbance difference spectra. The raw difference spectra between PFC and KH perfusion (blue line) is shown with the fitted spectra (red line) and the residuals of the fit (green line). C: the spectral contribution of each chromophore to the resulting fitted spectra shown in B. Each reference spectra was scaled by its fitting coefficient that was determined during the least-squares spectral fitting algorithm.