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Biomedical subjects

C R Wyss

Publications and source records attributed to C R Wyss.

31 records · Page 2Linked to original sources
PubMed1982

Segmental transcutaneous measurements of PO2 in patients requiring below-the-knee amputation for peripheral vascular insufficiency.

An accurate method is needed to quantitate the healing potentials of the possible sites of amputation in dysvascular limbs. We evaluated the segmental transcutaneous measurements of PO2 in thirty-seven patients who required below-the-knee amputation because of peripheral vascular insufficiency. The fifteen patients with below-the-knee transcutaneous PO2 values of forty millimeters of mercury or more had no delay in healing of the below-the-knee amputation. Seventeen of nineteen patients with values of more than zero but less than forty millimeters of mercury had healing at the below-the-knee level, in two after local revision. The three patients who had below-the-knee values of zero required re-amputation above the knee.

Aged↗
PubMed1981

Dependence of transcutaneous oxygen tension on local arteriovenous pressure gradient in normal subjects.

1. We studied the relationship between transcutaneous oxygen tension at the foot and local arteriovenous pressure difference in 15 normal men and women; arteriovenous pressure difference was varied by changing the height of the foot with respect to the heart and by applying external pressure to the foot. 2. Control transcutaneous oxygen tension was 67 +/- 9 SD mmHg (8.9 +/- 1.2 kPa) at a control arteriovenous pressure difference of 80 +/- 6 SD mmHg (10.6 +/- 0.8 kPa). 3. In every subject transcutaneous oxygen tension fell non-linearly with a decrease in arteriovenous pressure difference; transcutaneous oxygen tension was relatively insensitive to changes in arteriovenous pressure difference when arteriovenous pressure difference was high, but always fell sharply to zero at some positive arteriovenous pressure difference [range 13-34 mmHg (1.7-4.5 kPa)]. 4. An analysis of the data indicated that transcutaneous oxygen tension varied with arteriovenous pressure difference approximately as the oxygen tension of cutaneous venous blood under the sensor varied (in the absence of changes in cutaneous vascular resistance and oxygen consumption). 5. This analysis was supported by studies in three subjects in whom the oxygen tension of superficial venous drainage from a warmed hand or foot was measured along with transcutaneous oxygen tension while arteriovenous pressure difference was varied.

Adult↗
PubMed1980

Transcutaneous oxygen tension measurement in peripheral vascular disease.

To date, results of laboratory and clinical investigations suggest that transcutaneous pO2 measurements hold considerable promise as a technique for evaluating the adequacy of cutaneous circulation. The advantages of this technique are that it is simple to use, noninvasive and does not require the use of radioactive isotopes. Since the available data are, as yet, insufficient to confirm the reliability of this technique, a prospective study of segmental transcutaneous pO2 values in patients with peripheral vascular disease is being continued. These values are then being correlated with the subsequent clinical course.

Adult↗
PubMed1980

Effect of acute hemorrhage on transcutaneous, subcutaneous, intramuscular, and arterial oxygen tensions.

Although transcutaneous PO2 is a close approximation of arterial PO2 in most neonates, infants in shock often show lower transcutaneous than arterial PO2 values. For a better understanding of this discrepancy, we investigated the effect of acute hemorrhage on transcutaneous, tissue, and arterial PO2 in rabbits. With progressive hemorrhage, transcutaneous and tissue PO2 values declined steeply while arterial PO2 values did not. We speculate that the progressive decrement in transcutaneous and tissue PO2 value with hemorrhage is produced by diminished peripheral blood flow. Rather than representing a failure of the transcutaneous PO2 monitoring method, we speculate that transcutaneous hypoxia with shock may be a clinically valuable danger signal.

Animals↗
PubMed1980

Transcutaneous PO2: a potential monitor the status of replanted limb parts.

In animal and human investigations, transcutaneous PO2 proved to be a sensitive and rapid indicator of the patency of the artery and veins supplying a limb part. Furthermore, transcutaneous PO2 indicated the presence or absence of collateral circulation. Commercially available transcutaneous PO2 probes were easily applied to human fingers and dramatically reflected the compromise of finger circulation by the inflation of a blood-pressure cuff around the arm. Probe temperatures from 42 to 44 degrees C appeared to provide satisfactory sensitivity and safety. On the basis of these studies, we conclude that transcutaneous PO2 monitoring holds sufficient potential for the evaluation of replanted limb parts to deserve a clinical trial.

Animals↗
PubMed1976

Lack of humanlike active vasodilation in skin of heat-stressed baboons.

To discover whether humanlike active skin vasodilation occurs in a sweating, subhuman primate, four unanesthetized male baboons (Papio anubis) were heated (blood temp = 39-39.5 degrees C) before and after arterial administration of the alpha-adrenergic blocking agent phenoxybenzamine HCl. Hcat stress alone increased common iliac vascular conductance (CIVC) from 1.2 to 3.7 ml-min-1-mmHg-1 (averages). alpha-Blockade alone increased CIVC from 1.2 to 3.3 ml-min-1-mmHg-1. Heat stress subsequent to alpha-blockade further increased CIVC by only 0.4 ml-min-1-mmHg-1. Thus, most of the rise in CIVC caused by heat stress could be mimicked by alpha-blockade. If, as in man, the dominant means of raising skin blood flow were nonadrenergic active vasodilation, the response of CIVC to heating would far exceed that due to alpha-blockade. We conclude that, in baboons, humanlike active vasodilation of skin plays no significant role in CIVC response to heat stress. Thus, the baboon is not an appropriate model for investigation of control of human skin circulation during hyperthermia.

Animals↗
PubMed1975

Altered control of skin blood flow at high skin and core temperatures.

Five subjects were studied during periods of controlled increases and decreases in skin temperature (Ts) over the Ts range of 34-40 degrees C. One protocol was designed to observe changes in forearm blood flow (FBF) and heart rate (HR) with changes in core temperature (Tc; right atrial blood temperature and esophageal temperature were measured) with Ts held constant at two levels. FBF and HR changed linearly with Tc in the Tc range of 37-38 degrees C with Ts constant at 38 degrees C. A second protocol imposed Ts changes at two levels of Ts and Tc; this protocol also included a prolonged cooling period. The influence of Ts on FBF and HR was reduced when Ts changes occurred at an elevated Ts and Tc, and FBF showed considerable hysteresis during cooling. We conclude that a linear model for the control of FBF or HR is inadequate as a tool for predicting the control of these variables.

Adult↗
PubMed1975

A high accuracy linear rate meter.

By implementing analog computer techniques using digital circuits, an instantaneous rate meter was built with approximately 100 times the accuracy of commercially available rate meters. The circuit is accurate to within +/- 0.2 events/min over a range of rates of 0.2-900 epm. Modifications can be made to provide a digital display of rate. The circuit design techniques used in developing the rate meter may be used to generate a wide variety of functions of time with very high accuracy.

Animals↗
PubMedDate not supplied

Factors affecting the tolerance of muscle circulation and function for increased tissue pressure.

The tolerance of neuromuscular tissue for increased tissue pressure has been observed clinically to vary among individuals. In experimental operations on rabbits, various factors may affect tissue pressure tolerance. Arterial hypoxia, halothane anesthesia, local arterial occlusion, and acute hemorrhage each reduced the amount of pressure necessary to produce circulatory and functional deficits. Extrapolation of these observations suggest that patients with hemorrhage, arterial hypoxia, and peripheral vascular disease may be at greater risk from a given tissue pressure than patients without these conditions.

Action Potentials↗