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We have developed a computerized system whereby the fetal heart rate can be recorded telemetrically from patients' homes, transmitted over conventional public telephone lines, and then computer-processed in real time in the obstetric unit.
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Methods are presented for measuring vertical force components on bridged titanium dental implants in dog mandibles. These methods have included custom-made strain-gauge transducers, plus hard-wiring and telemetric schemes for data collection. The essential components of the measurement system are described, and typical bite force data are illustrated.
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In normal chewing the forces exerted on the occlusal surface seldom exceeded 10 to 15 pounds, as recorded by an eight-channel force transmitter in a removable fixed partial denture. Ninety-five percent of forces were less than 3.5 pounds for subject A, 2.0 pounds for subject B, and 10.0 pounds for subject C. The chewing frequency and the places of maximal force on the occlusal surface were relatively constant. The electromyographic chewing patterns could be considered normal in all circumstances. There was a remarkable statistically significant day-to-day variation in force values. The forces also changed for different kinds of food. The differences between maximum and minimum force values were highest in voluntary, nonfunctional movements.
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The radiotelemetry system described in this paper consists of an implantable transmitter and a receiver, connected to a microcomputer. The hardware and software belonging to Mini-Mitters, for the collection and analysis of heart rate (HR), core temperature (CT), and gross activity data, do not possess the flexibility to detect acute changes in HR nor to discriminate among simultaneously occurring different types of behavior. In order to study short-term changes in HR in response to stress or drugs, in relation to behavioral responses, an inexpensive computer interface and a software program (CARDIAQ) were developed to collect data from Mini-Mitters. The interface conveys the QRS signal, which is converted to a TTL pulse train, to the parallel printer adapter (LPT1) of an IBM-compatible computer. Heart rate is determined by measuring single interbeat intervals (IBI). The software controls the sampling schedule and stores the collected data in a format compatible with a commercial spreadsheet package. The program calculates the median IBI per s, mean +/- SD IBI, variance, skewness, and kurtosis of the IBI distribution. In addition, it enables simultaneous recording of behavior by entering data through the keyboard at the occurrence of each event. In this paper, we describe the CARDIAQ program and provide examples of its application together with the implantable transmitters in freely moving rats.
Male Long-Evans rats were implanted with blood pressure transmitters and introduced as intruders for 60 min into the home cage of a reproductively active resident male rat. Physical interaction ended after 3-5 min when the intruder displayed clear submissive behaviors. A protective wire cage was placed over the intruder until the animal was returned to its home cage. Systolic (+29.3 +/- 3.6 mmHg) and diastolic (+25.7 +/- 3.7 mmHg) blood pressures, pulse pressure (+7.3 +/- 2.0 mmHg), and heart rate (+129.0 +/- 12.6 BPM) peaked in the intruder rats during the defeat and did not fully return to control levels until return to the home cage. These acute changes as well as the heart rate and blood pressure baselines did not change when the confrontations were repeated on alternating days for a maximum of three trials per week. Pretreatment with clonidine (0.01, 0.03, 0.06, and 0.1 mg/kg) led to a dose-dependent decrease in the heart rate response but blood pressure was reduced similarly for all doses. We conclude that acute "defeat" can lead to an abrupt, large increase in blood pressure and heart rate in normotensive, Long-Evans rats that is sustained even in the absence of physical contact with the threatening resident. This response is diminished but not prevented by administration of clonidine.
The change in body temperature of the rat is commonly measured using biotelemetry or the rectal probe. The authors report that the two methods yield qualitatively similar but quantitatively different results in two experiments. In Experiment 1, both methods detected a salicylate-affected reduction in handling-induced hyperthermia. In Experiment 2, both methods were useful in detecting the hypothermia induced by the muscarinic agonist oxotremorine. In both Experiments 1 and 2, measurements of baseline temperature were higher when measured with the rectal probe. Baseline temperature is measured with biotelemetry prior to handling animals, whereas the act of measuring baseline temperature with the rectal probe necessitates handling. The investigators hypothesized that a rise in baseline temperature produced by handling at least partially accounts for the greater hypothermic response obtained in Experiment 2 using measurements obtained with the rectal probe. In Experiment 3, baseline temperature was measured with biotelemetry after animals were handled. Handling produced an increase in baseline temperature. The hypothermic response to oxotremorine was increased when the higher posthandling baseline temperature was used to calculate the hypothermic response of animals. The authors conclude that differences in baseline temperature and hypothermic response obtained with the two methods are related to an effect of handling.
This paper describes an electronic clinical thermometer which does not require a cable connection between the sensor and the temperature indicator. Several patients using individual battery-powered sensors can have their temperatures logged by a hand-held interrogating device held in close proximity. Temperature readout is virtually instantaneous and there is no interference between adjacent users. The device relies on radiofrequency-tuned circuit coupling for its operation.