An exception to the categories proposed above exists in that workhorse of clinical methods: the physical exam. Nearly as old as the medical field itself, the physical exam is one of the first lines of inquiry to assess many facets of patient health. The same is true when attempting to assess volume status. Studies have found the most useful parameters of the physical examination to be pulse excitation in response to postural changes (≥30 beats per minute) and dizziness for diagnosing hypovolemia in patients and paroxysmal nocturnal dyspnea, orthopnea, and peripheral edema for diagnosing hypervolemia in patients. These studies were conducted on patients with acute blood loss and heart failure, respectively, and their applicability beyond these types of patient populations is not documented. When asked to predict hemodynamic variables obtained via pulmonary artery catheterization, physicians did so correctly 24-55% of the time. Such findings indicate to many that a physical examination alone is insufficient to predict the volume status or responsiveness of a patient.