Roland Heinze

Central venous oxygen saturation for the control of automatic rate-responsive pacing.

A rale‐adjusting pacemaker system is described which uses central venous oxygen saturation (SO2) for the regulation of the pacing rate. This system was tested externally in ten patients with chronically implanted VVI units. There was an average increase in cardiac output of 18% with the SO2‐regulated pacemaker as compared to the situation during fixed rate stimulation. Central venous oxygen saturation appears to be an ideal biological parameter for autoregulating the pacing rate. It represents the only sensor suitable for the realization of a closed feedback loop concept

Phase-related changes in right ventricular cardiac output under volume-controlled mechanical ventilation with positive end-expiratory pressure.

OBJECTIVE To examine determinants of right ventricular function throughout the ventilatory cycle under volume-controlled mechanical ventilation with various positive end-expiratory pressure (PEEP) stages. DESIGN Prospective observational animal pilot study. SETTING Animal research laboratory at a university hospital. SUBJECTS Eight healthy swine under volume- controlled mechanical ventilation. INTERVENTIONS Flow probes were implanted in eight swine in order to continuously measure blood flow in the pulmonary artery and inferior vena cava. After a recovery phase of 14 days, the swine were subjected to various PEEP stages (0, 5, 10 cm H2O) during volume-controlled positive pressure ventilation. MEASUREMENTS AND MAIN RESULTS Continuous flow measurement took place in the pulmonary artery and inferior vena cava. Data on standard hemodynamic parameters were additionally acquired. Respiration-phase-specific analysis of right ventricular cardiac output and of additional hemodynamic function parameters followed, after calculation of mean values throughout five respiration cycles. PEEP at 5 cm H2O led to significant decreases in inferior vena cava flow (4.1%), and in right ventricular cardiac output (5.2%); the respective decreases at PEEP 10 cm H2O were 13.9% and 18.3%. In the inspiration phase at PEEP 10 cm H2O, results revealed an overproportionally pronounced decrease in comparison with the expiration phase in inferior vena cava flow (-24.6% vs. -10%) and right ventricular cardiac output (-35% vs. -13.5%). This phenomenon is presumably caused by a PEEP-related increase in mean airway pressure by the amount of 10.7 cm H2O in inspiration. CONCLUSIONS Increases in PEEP during volume-controlled mechanical ventilation leads to respiration-phase-specific reduction of right ventricular cardiac output, with a significantly pronounced decrease during the inspiration phase. This decrease in cardiac output should be taken into particular consideration for patients with already critically reduced cardiac output.

An Active Optical Sensor for Monitoring Mixed Venous Oxygen-Saturation for an Implantable Rate-Regulating Pacing System

Les stimuJateurs dits “physiologiques” qui sont actuellement disponibles ne restaurent pos la fréquence optimale dans les cos de défaillance auriculaire. ?autres paramètres biologiques doivent servir de stimulus physiologique pour determiner ľouto‐reglage de la fréquence. La saturation veineuse mesurée par capteur optique serait probablement le paramètre idéal pour ce système de sfimulation. Des recherches supplémentaires sont nécessaires pour bien déterminer les modalités des reponse du système.

A new multisensor pacing system using stroke volume, respiratory rate, mixed venous oxygen saturation, and temperature, right atrial pressure, right ventricular pressure, and dP/dt.

A new multisensor pacing device using respiratory rate (RR), stroke volume fSV), oxygen saturation (SO2), temperature (T), right atrial pressure (RAPJ, right ventricular pressure (RVPJ and right ventricular dP/dt, has been developed. It consists of a 7F multisensor catheter and an external pacing unit. It allows simultaneous recording of the input signals and the corresponding data can be compared among the different parameters under identical conditions. Furthermore, several parameters can be combined in such a way as to form a new combination better suitable for rate responsive pacing. The response of each parameter to exercise was studied in 12 healthy volunteers (mean age:28 years). Exercise testing was carried out using a bicycle ergometer, with workloads up to 200 W. The dynamic characteristics, response and sensitivity to changes of workloads of each parameter were analyzed and compared to one another. SO2 proved to be a quick responding parameter (<10 sec) with higher sensitivity in the low exercise range (<75 WJ, T, on the other hand, responded slowly (>30 sec) to exercise changes and had the highest sensitivity in the exercise range beyond 75 W. RR displayed a slow response (>30 sec) and an adequate sensitivity was only found in the upper exercise range (>100 W). SV reacted rapidly to workload changes (<10 sec) but showed poor sensitivity at all exercise levels. RAP, RVP and dP/dt displayed quick responses and constantly good sensitivity throughout the workload range. Furthermore, respiratory rate was easily‐derived from the RAP curve. Special algorithms were developed for each parameter so that pacing rate would reproduce sinus rate behavior. We found that SO2 and all pressure parameter imitated sinus rate response quite well. When using parameter combinations, SO2 and T proved to be superior. Five patients (mean age 68 years) with third degree AV‐block were stimulated temporarily using this system. Compared to fixed rate stimulation [VVI 70], exercise performance improved, using SO2 as the input parameter for rate response, by 25% to 50%.

First Clinical Experience with an Oxygen Saturation Controlled Pacemaker in Man

This article describes the characteristics of a new implantable pacemaker controlled by right atrial oxygen saturation and reports the first clinical experience in man. During the observation period over 5 months, there was no evidence of malfunction due to tissue growth. The systems reaction to exercise changes proved to be quick (5 s to 17 s); decay times varied depending on the magnitude of the power previously performed. Under various exercise tests, the rate increase was linear to the stress load. Measurements of cardiac output showed the systems hemodynamic feedback and its potential self‐optimization of pacing rate.

Rate control with an external SO2 closed loop system.

In 20 volunteers (mean age 35.5 y) and 12 pacemaker patients (mean age 68.7 y), central venous oxygen saturation (SO2) was monitored continuously by means of an optical sensor integrated in an external transvenous pacing lead placed in the right ventricular cavity. From the SO2 signal recorded at rest and during various modalities of exercise, an algorithm for controlling pacing rate of an external pacing system was developed. An open loop system was used in the volunteers, allowing the comparison of the computed pacing rate with the individual intrinsic heart rate. There was an excellent correlation between the two frequencies as far as the dynamic characteristics and the steady state relationship were concerned. In five pacemaker patients who were stimulated via the external lead, a closed loop control of pacing rate was used. In one patient with a DDD pacemaker implanted for third degree AV‐block, the rate response of the SO2 driven pacemaker was well in accordance with the rate attained with the implanted atrial triggered system. With both pacing modes, exercise capacity as determined on a symptom limited treodmill test was identical. In four patients (3 AV block III, 1 bradyarrhythmia) an improvement in exercise tolerance up to 65 percent could be demonstrated with the rate responsive pacing mode. In all patients, it could he shown that an autoregulating pacemaker system with SO2 is an open possibility.