Cardiac Output Pulmonary Arterial Catheter Compared to FloWave™ 1000

Inclusion Criteria: * Adults Only: The FloWave device is intended for use on adult patients only. All subjects will be 18 years or older. * Existing placement of a Pulmonary Arterial Catheter placed for medical reasons other than our study. Exclusion Criteria: * Patients with aortic balloon pumps and cardiac mechanical assist devices will be excluded from study enrollment if the devices are present during the screening process. If patients have cardiac assist devices inserted after enrollment in the study, cardiac output data will be collected with both the PAC and FloWave device and will be evaluated as a subset analysis population at the conclusion of the study. * Patients with intracardiac shunts will be excluded from this study. * FloWave cardiac output determinations are dependent on detection of a pulse. If no peripheral pulse can be detected the device will not be able to perform a measurement and this will be indicated to the user. * Patients who are not in a steady hemodynamic state shall be excluded from the study. * Presence of arrhythmias: Patients with arrhythmias are excluded from the study when not in a steady hemodynamic state. If a patient has a history of arrhythmia or is currently experiencing an arrhythmia but is in a maintained hemodynamic state, they will not be excluded from enrollment into the study. Their clinical symptoms and cardiac rhythm will be evaluated and noted in the patient data record. * Inability or unwillingness of subject or the subject's legally authorized representative to give informed consent.