ABSTRACT
The significance of age-related changes in arterial stiffness has remained largely uncertain in healthy subjects. This appears to be partly due to difficulties in the interpretation of methods for measuring arterial stiffness in vivo. Therefore, a recently developed electrical bioimpedance method was used for studying elastic properties of a vascular bed as a function of age. In 66 healthy subjects, aged 22-82 years, we investigated the vascular bed of an upper arm segment. This vascular bed showed an age-related decrease in the venous blood volume (r = -0.31, p < 0.01) and in the distensibility, the inverse of stiffness, of the larger arteries (r = -0.38, p < 0.001). The distensibility of the arterial bed as a whole at normotensive blood pressure, however, appeared to increase with age (r = 0.32, p < 0.005). The arterial and venous blood volumes, arterial compliance and extravascular fluid volume were significantly higher in the males than in the females. Practically all investigated vascular properties appeared to be related with height, body mass or body mass index. We concluded that comparative studies concerning vascular properties should preferably be performed in subjects matched as to age, gender, height and body mass. In healthy subjects the smaller arteries adjust to the age-related decrease in large artery distensibility by means of an age-related increase in distensibility. These age-related changes in arterial distensibility are caused by changes in the females, and seem to be associated with age-related changes in body mass index rather than with aging per se.
Subject(s)
Aging , Arm/blood supply , Elasticity , Adult , Aged , Blood Pressure , Body Height , Body Mass Index , Body Weight , Compliance , Female , Humans , Male , Middle AgedABSTRACT
In ten vagus nerves the effect of local cooling on the compound action potential was studied in the temperature range of 34 to 0 degrees C in spontaneously breathing, anaesthetized rabbits. The mean temperature at which the myelinated (A) fibres were completely blocked, was 10.2 +/- 2.4 degrees C (mean +/- S.D.). In nine nerves, local vagus cooling to 0 degrees C failed to block all non-myelinated (C) fibres. In one nerve, total blocking occurred at 2.0 degrees C. We conclude that in the rabbit, the earlier found increase in tonic activity of the diaphragm following lung inflation or deflation during bilateral local vagus cooling to a temperature between 8 and 0 degrees C is due to afferent impulses in vagal C fibres.
Subject(s)
Cold Temperature , Nerve Fibers/physiology , Neural Conduction/physiology , Reflex/physiology , Respiration/physiology , Action Potentials/physiology , Animals , Chinchilla , Female , Male , Nerve Fibers, Myelinated/physiology , Rabbits , Vagus Nerve/cytology , Vagus Nerve/physiologyABSTRACT
A flexible glass electrode catheter with a diameter of 3 mm has been developed for pH measurement in the arterial system of dogs. In combination with a galvanically isolated amplifier, an undisturbed pH signal could be obtained from the aorta. The system was fast enough to truly record pH changes synchronous with respiration and was shown to be insensitive to variations in blood flow velocity. Good agreement was found between pH catheter readings nd pH values of simultaneously taken arterial samples as measured with a conventional capillary glass electrode.
