Figure 2.

Classes of Brain pulses. The uppermost panel demonstrates a normal Arterial compression brain pulse. The pulse has similar shape to a normal arterial pressure waveform. The next panel demonstrates a Low compliance brain pulse has a shape like an invasively measured low brain compliance or high intra-cranial pressure waveform, with a delayed time to P2 and high P2/P1 ratio, an A wave may be present. It has clear and distinct features consistent with increased blood volume in the pial venules. The Hybrid brain pulse 940 and 660 nm pulse shapes are quite distinct from each other and may also have some venous pressure features including subtle A, X, C, V and Y waves, consistent with reduced arteriole pressure levels. The Venous I brain pulse has somewhat undifferentiated features. Consistent with similar arteriole and central venous pressure levels throughout the cardiac cycle. The start of the pulse may be difficult to determine. Commonly a trough is present in the diastolic phase consistent with a Y wave. The systolic phase of the pulse may have discernible Arterial brain pulse features. The 660 and 940 nm pulses have similar shapes. The Venous II brain pulse is like the Venous I but demonstrates clear central venous waveform features though out the cardiac cycle. The combination of a X wave (in systole) and the Y wave (in diastole) suggest arteriole pressure is lower than the central venous pressure throughout the cardiac cycle. The Weak brain pulse is characterized by a low pulse amplitude < 1000 AU and prominent jitter throughout and is consistent with very low cerebral blood flow. Red brain pulse is 940 nm and blue brain pulse 660 nm. The yellow area represents the systolic phase of the cardiac cycle and the white the diastolic phase.