Plethysmography without venous occlusion for measuring forearm blood flow: comparison with venous occlusive method.

Limb blood flow is widely used as an indicator of the human vascular properties. There are only few non-invasive methods for its measurement such as venous occlusion plethysmography. However, several authors have questioned its validity.

Blood flow measurement from plethysmographic pulse waves without venous occlusion.

An air plethysmograph with a sensitive phototransducer was constructed so that plethysmographic volume-change pulsations could be displayed in detail without using venous occlusion. Software was developed to allow analysis of the pulses using a modification of the backward extrapolation technique. This allowed calculation of the forward arterial blood flow and noninvasive derivation of the resting arterial flow waveform.

Plethysmographic curve analysis and response to exercise in normal subjects, hypertension, and cardiac failure.

Occlusion plethysmographic recordings were obtained on 26 subjects prior to and immediately following repeated venous occlusions. A simple method of approximating the curve shape by 2 straight lines is described. The results indicate that, following an initial occlusion, the height of subsequent curves is reduced and the angulation between the 2 lines approximating the curves changes in a way that indicates that the principal mechanism is venous shunting.

Low-level direct electrical current therapy for hepatic metastases. I. Preclinical studies on normal liver.

Low-level direct electrical current has shown promise as a potential therapeutic modality (direct current therapy; DCT) in the treatment of malignant disease, including metastases, but to date much experimental work has been empirical and has added little to our knowledge of the mechanisms involved. As a prerequisite to a clinical trial for metastases in the liver, we have employed an in vivo liver model to examine the quantitative and qualitative relationships between electrode polarity, charge and tissue necrosis. Two distinct regions of necrosis were induced, distinguishable histologically and by magnetic resonance imaging: (i) a cylindrical region of primary necrosis centred on the electrode, its volume directly proportional to the charge passed, but greater at the anode than cathode; and (ii) a wedge-shaped infarct, apex at the electrode and base extending to the liver edge.

Ablation of neoplasia by direct current.

The application of low-voltage direct electrical current (DEC) has been studied in animals and humans for the ablation of anal condylomata, oesophageal cancer and Kaposi's sarcoma. Twenty milliamps of DEC passed through multiple 6 cm x 1 cm, flat-plate longitudinal electrodes into the squamous mucosa of the oesophagus of healthy dogs for periods ranging from 10 min to 2 h resulted in denudation and necrosis of the oesophageal mucosa at the site of application of the current. In humans, the application of DEC to two patients with benign anal condyloma acuminata, three patients with inoperable obstructing oesophageal cancer and one patient with disseminated Kaposi sarcoma resulted in striking necrosis of tumour tissue that was confirmed by macroscopic and microscopic studies.