Biomedical subjects

H Theres

Publications and source records attributed to H Theres.

39 records · Page 3Linked to original sources

PubMed1987

[Effect of respiration on variations of central venous blood temperature].

We examined the course of right ventricular blood temperature before, during and after treadmill exercise in three patients with implanted cardiac pacemakers, and in two healthy volunteers. Temperature measurements were performed with a specially developed 5F electrode with an incorporated thermistor (measurement accuracy: 1/100 degrees C). After electronic amplification, the temperature signals were recorded on a three-channel strip chart recorder, together with ECG and respiration (measured by impedance plethysmography). In one of the volunteers, blood flow in the jugular and femoral veins was recorded by Doppler sonography, before and after exercise. We observed a decrease in central venous blood temperature with inspiration and an increase with expiration before, during and after exercise. The amplitudes of the variations became smaller during exercise, reached a maximum immediately after exercise and returned to their resting values within a few minutes after the end of exercise. We suppose different distributions of venous blood flow in different phases of the respiratory cycle to be the reason for the respiration-induced variations in central venous blood temperature. Under exercise conditions, the influence of respiration on the blood flow in the larger veins is small compared to the influence of an increased cardiac output; at rest, respiration has a more pronounced effect on venous blood flow. The analysis of our blood flow measurements in the femoral and jugular veins supported this assumption.

Adult↗

PubMed1986

Measurement of right ventricular blood temperature during exercise as a means of rate control in physiological pacemakers.

Several biological parameters have been suggested for rate control in physiological pacemakers in the past. Up to now, measurements of central venous blood temperature have been mostly done on dogs. We studied central venous blood temperature and heart rate in 14 healthy volunteers under conditions of treadmill and bicycle exercise with different workloads. A custom-made 5F lead with a thermistor incorporated near the tip was placed at the right ventricle under fluoroscopic control. Temperature was recorded with an accuracy of 1/100 degrees C on a digital memory device at a sampling rate of 5-10 s. We found the increase in blood temperature to be not only a function of absolute workloads but also a function of the individual's maximum exercise tolerance. Independent of the absolute increase in heart rate and temperature at a given workload, the individual's relation of increase in temperature and heart rate was found to be highly correlating (r = 0.9095). At a load of 100 W, we found a mean increase in heart rate of 52 beats and of temperature of 0.57 degree C, at 150 W of 74 beats/min and 0.84 degree C. During, as well as after, the exercise, heart rate and temperature have a parallel course. According to our data, control of physiological pacemakers by means of central venous blood temperature is possible.

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PubMedDate not supplied

Central venous blood temperature for rate control of physiological pacemakers.

In 17 pacemaker patients and 14 volunteers we studied the behaviour of central venous blood temperature and heart rate under different kinds of exercise. Data were recorded by means of 5F catheter placed at the right ventricle. Temperature was measured with a thermistor incorporated in the lead. We found the increase in central venous blood temperature to be dependent on the individual exercise capacity and work load performed. The maximum temperature increase seen was 1.7 degrees Celsius. Subjects with lower physical fitness showed a more pronounced increase in temperature and heart rate compared to more physically fit subjects at the same work load. Due to its close relationship to metabolic and circulatory parameters, central venous blood temperature represents an appropriate signal to control the rate of physiological pacemaker systems. A special algorithm also using the initial dip for rate control has been incorporated into a pacemaker system, that is currently under clinical investigation (Intermedics NOVA MR).

Adult↗