Plethysmography: safety, effectiveness, and clinical utility in diagnosing vascular disease

Plethysmography, a semiquantitative method of measuring segmental blood flow and velocity in the carotid and peripheral vascular systems, is safe, easy to perform, and inexpensive. Impedance, strain guage, air, and photoelectric plethysmographic methods are assessed in this publication for their relative safety, efficacy, and clinical utility in diagnosing vascular disease. Clinical evidence has demonstrated, for example, that oculoplethysmography is not a reliable screening test for carotid artery disease, particularly in bilateral disease and nonocclusive unilateral disease. Oculoplethysmography is thus no longer recommended for the diagnosis of carotid artery disease. Impedance, strain guage, and photoplethysmography methods can be used for the initial evaluation of acute and chronic venous insufficiency, although there is great variability in the reliability of these tests to predict venous disease in the presence of nonobstructive thrombi and comorbid conditions. Strain guage and photoelectric plethysmography can be safely used for the evaluation of peripheral arterial disease. But surgical candidates for arterial reconstruction and some venous disorders may require additional imaging such as duplex ultrasound, venography, or arteriography for anatomic information that is not elucidated by plethysmography. The plethysmographic techniques reviewed in this assessment, evaluating the ability to predict the presence of flow reduction in the carotid and peripheral circulations, are based on the technical performance of the tests as compared with a reference method. Establishing evidence-based conclusions proved difficult in light of biases such as nonrandomization, unstated patient selection criteria, poor followup of patients, and lack of blindness in some studies.