Noninvasive Blood Pressure Monitor Evaluation Including Performance During Dysrhythmias

Inclusion Criteria: * signed informed consent * a patient who is undergoing a specialized procedure such as a surgical procedure or cardiac catheterization, or during critical care monitoring in which a central arterial catheter is in place to determine systolic, diastolic, and/or mean arterial blood pressure values. * ability to monitor ECG, NIBP and/or pulse oximetry * presence of atrial fibrillation, atrial flutter, or normal sinus rhythm Exclusion Criteria: * any subject deemed too unstable, at the clinician's discretion, to participate in the study * any subject with a cardiac or vascular malformation that results in an abnormal waveform inappropriate to be considered a reference standard * any subject with a cardiac anomaly that would cause a disparity between aortic pressures and the periphery. * presence of peripheral vascular disease in arms * inability to perform a minimum of 4 fast flushes (two at the study beginning and two at the study end) on an arterial catheter or line in order to determine a frequency response. The volume of fluid will not exceed a total pre-specified by the Principal Investigator or designee. * if the baseline arm to arm mean difference is \> 10 mmHg, then the differences will be recorded and evaluated by the Principal Investigator for possible subject exclusion from the data analysis. * subjects who, at the clinician's discretion, could not tolerate approximately 5 to 12, but possibly up to 25 repeated blood pressures on each arm