Abstract: A system using combined electrocardiography (EKG) and photoplethysmography (PPG) sensing to assess intra-arterial fluid volume is described. The system uses averaging of similar pulses based on prior (n?1; n minus 1) R-to-R pulse wave duration, and prior-prior (n?2; n minus 2) R-to-R pulse wave duration, to determine a patient's fluid status and whether it is below or above optimal intravascular hydration.

Abstract: A system using combined electrocardiography (EKG) and photoplethysmography (PPG) sensing, to determine venous oxygen saturation is described. The system uses averaging of similar pulses based on Prior (or n?1) R-to-R pulse wave duration, and current (or n) R-to-R pulse wave duration for evaluation of the metabolic reserve and/or stress of the patient.

Abstract: A system for synchronizing a target device to a cardiac cycle, including: (a) a target device that collects data or performs an operation that is to be timed to the cardiac cycle; (b) a signaling device that emits a signal indicating the occurrence of a cardiac contraction and/or ECG feature; and (c) a calibration device that determines the relationship of the signal from the signaling device to the actual cardiac cycle. In operation, the calibration device calculates a time offset between the timing of the cardiac contraction as determined by the signaling device and the timing of the cardiac contraction and/or ECG feature as determined by the calibration device, and then provides the time offset to the target device.