A method for measuring a myocardial physiologic parameter according to an embodiment includes placing an at least partially convex portion of a spectral sensor against an intercostal space of a human over a heart of the human and measuring the physiologic parameter of a myocardium of the heart with the spectral sensor over time during an emergency medical event. The spectral sensor may be configured to determine and visually display a suggested position adjustment for directing the spectral radiation more directly toward the tissue of interest (e.g. the myocardium), and/or for placing the operative elements of the spectral sensor closer to the tissue of interest (e.g. the myocardium).