The reduction of peripheral blood flow, which occurs during shock or in patients with occlusive arterial disease of the lower limb is accompanied by an increase in hydrogen ion activity in tissue cells. If this change could be measured, it could possibly be used as an indicator of tissue perfusion in such patients. Investigations have been carried out into various pH microelectrode designs in order to construct one which could be used clinically to measure extracellular pH changes in skin. Experiments with antimony and externally insulated glass micro-electrodes demonstrated that these were unsatisfactory for the purpose. The successful design was insulated internally by means of a glass to glass fuse. It was robust, stable, sensitive and had a fast response time. Use of the electrode in normal volunteers produced reproducible skin pH values and demonstrated the feasibility of the system. Preliminary results using the micro-electrodes in patients indicate their possible application to the assessment of peripheral vascular disease, and to the monitoring of patients under intensive care.

Antimony↗

PubMed1979

Micro-electrode measurement of skin pH in humans during ischaemia, hypoxia and local hypothermia.

1. The extracellular pH value in the dermis of human skin (skin pH) was measured in vivo using glass micro-electrodes. They were found to be both reliable and accurate. 2. The mean value of skin pH measured in the legs of forty different volunteers was found to be pH 7.54 +/- 0.09 (S.D.). No difference in skin pH was observed between males and females, or in different regions of the limb. 3. Local reductions in skin surface temperature in ten subjects caused an increase of pH 0.023 +/- 0.007 per degree C fall. 4. A 20 min period of tourniquet ischaemia in twenty volunteers induced a fall in skin pH of 0.13 +/- 0.05 units. 5. Hyperventilation during a 10 min period of breathing 10% O2 in N2 caused an increase of pH 0.04 +/- 0.02 in the skin of healthy subjects. 6. Skin pH fell to a value 0.02 +/- 0.02 units below normal 10 min after the hypoxic period, suggesting the presence of excess lactate. 7. Skin pH results compared well with blood gases and pH values of arterialized samples taken during hypoxia. 8. It was concluded that the system was suitable for clinical trials.

Adult↗

PubMed1978

Tissue pH measurement [proceedings].

Explore the source record for details and available documents.

Animals↗

PubMed1977

A new design of glass micro-electrode for extracellular pH measurement [proceedings].

Explore the source record for details and available documents.

Hydrogen-Ion Concentration↗

PubMedDate not supplied

Oxygen extraction rates in inflamed human skin using the tuberculin reaction as a model.

The microcirculation of inflamed human skin was assessed non-invasively using the techniques of laser Doppler flowmetry, hydrogen clearance flowmetry, visible-light spectrophotometry and transcutaneous oximetry. Increases in red cell flux (from a mean of 1.1 in normal skin to 11.5 V in inflamed skin) and haemoglobin saturation (from 49 to 87 and from 38 to 60% with macro- and micro-light-guide spectrophotometry, respectively), contrasted with decreases in transcutaneous pO2 (from 86 to 39 mm Hg). The more intense reactions tended to lead to a lower value of oxygen tension at the surface of the skin than the weaker reactions. A barrier to oxygen diffusion, presented by the infiltrating inflammatory cells, has previously been suggested as the reason for this. The oxygen extraction rate was estimated from spectrophotometry and blood flow measurements, using the Fick principle, and this showed an increase (from 42 to 130 arbitrary units, AU). When the skin was heated to 44 degrees C there was no change seen in this parameter in inflamed skin compared with normal skin (from 114 to 133 and from 14.1 to 14.5 AU), although it tended to increase in the stronger reactions while decreasing in the weaker ones. Extraction measured by a cuff occlusion method (with the same skin temperature) did show an increase however (from 28 to 57 and from 3.2 to 7.2 AU), and this was more pronounced in the stronger reactions. It is suggested that there may be a critical transit time for a red cell, during which it is able to effectively off-load its oxygen. In conditions of very high flow the transit time is reduced and oxygen extraction may be compromised further when diffusion is already limited.

Adolescent↗

PubMedDate not supplied

Gender, age and carotid plaque morphology.

OBJECTIVES: To examine the relationship between patients gender, age and the development of different types of internal carotid artery plaque. DESIGN: Prospective open clinical study. METHODS: 455 carotid duplex scans with a greater than 50% stenosis were analysed in terms of gender, age, degree of stenosis symptoms and plaque morphology. RESULTS: There were 238 males (52.3%) and 217 females. Of 120 patients with type I plaque 86 were male (71.7%, chi 2 = 23.4, p = 0.000002). This high incidence of type I (haemorrhagic) plaque in men was accompanied by a higher degree of stenosis (chi 2 = 11.7 p = 0.0006) but was independent of the age of the patients and the presence of symptoms. CONCLUSIONS: Although this study supports the view that men have more severe carotid artery disease, it does not to affect a younger age group. The higher degree of stenosis and its association with haemorrhagic plaque is not translated into an increase in symptoms in men.

Adult↗