NFC Powered Implantable Temperature Sensor.

Inductively powered 99% accurate implantable temperature sensor is designed, characterized and the findings are presented in this paper. The implantable sensors deliver a continuous temperature reading to external storage or readout devices via Near Field Communication interface. A 2.76µH rectangular inductive coil printed on a thin biocompatible plastic substrate is designed to establish the coupling link through NFC interface with external readout devices. A commercially available wide range temperature sensor chip is mounted along with the developed inductive coil on the same plastic substrate. For 50 samples, the received signal strength indicator, temperature accuracy and statistical distribution of measurement levels is investigated. Comparison of predetermined temperature in a controlled temperature and humidity chamber versus the temperature reading from the developed sensors proves a 99% accuracy.

Inspiratory resistive load detection in children with life-threatening asthma.

The detection of inspiratory resistive (R) loads was studied in nonasthmatic children (NA), asthmatic children (A), and children with a history of life-threatening asthma (LTA). It was hypothesized that the LTA children would have a reduced ability to detect added mechanical loads as measured by the Weber fraction, which assesses the resistive load detection threshold (DeltaR(50)/R(0)). Subjects were separated from the investigator, were seated in a soundproofed room, and breathed through a nonrebreathing valve with the inspiratory port connected to the loading manifold. The subject's inspiratory baseline resistance (R(aw)) was measured by the interrupter method. Ten magnitudes of R loads and no-load were presented randomly 10 times each for a single inspiration. The loads were presented in three trials. Subjects pressed a button if they detected the presence of a load. The DeltaR(50) was determined from the % detection-DeltaR curve. R(0) was the sum of the subject's R(aw) and the minimal resistance of the apparatus. The DeltaR(50)/R(0) for children with life- threatening asthma was significantly greater than for asthmatic and nonasthmatic children. The increased DeltaR(50)/R(0) suggests that children with LTA are at risk of life-threatening asthma attacks, in part because it requires a greater change in resistance above their baseline resistance before they sense an increased mechanical load such as presented to them by bronchoconstriction during an asthmatic attack.

Respiratory-related evoked potentials in children with life-threatening asthma.

Respiratory-related evoked potentials (RREPs) have been elicited by inspiratory occlusion and recorded over the somatosensory cortex. The first positive peak (P(1)) amplitude has been correlated with the magnitude of inspiratory loads. Since children with life-threatening asthma (LTA) have a decreased perceptual sensitivity of inspiratory loads, we hypothesized that a subpopulation of patients with LTA have an impaired ability to sense mechanical loads, and that these patients would have an abnormal RREP. The RREP was recorded from C(Z) -C(3) and C(Z) -C(4) in three groups: LTA asthmatic, control asthmatic, and nonasthmatic children. Two inspiratory-interruption occlusions trials and a control trial were recorded. All the evoked potentials were analyzed after the averaged control trial was subtracted from the averaged occlusion trials. The RREP P(1) peak was observed in all 14 nonasthmatic children and in 14 of 15 control asthmatic children. The RREP was absent in 6 of 11 patients with LTA. When present, there were no between-group significant differences in P(1) peak latency or amplitude. These results demonstrate that the RREP elicited by inspiratory occlusion is present bilaterally in nonasthmatic and asthmatic children. There is a subpopulation of LTA children in which inspiratory occlusion fails to elicit the P(1) peak of the RREP, suggesting an altered neural processing of inspiratory load information.

Magnitude estimation of inspiratory resistive loads in children with life-threatening asthma.

The perception of inspiratory resistive (R) loads was studied in nonasthmatic children and in children with a history of life-threatening asthma. It was hypothesized that the children with life-threatening asthma would have a reduced sensitivity to added mechanical loads as measured by magnitude estimation of resistive loads (ME). The subjects were screened from the experimenter and seated in a sound-isolated room in a lounge chair facing an oscilloscope, and they respired through a nonbreathing valve with the inspiratory port connected to the loading manifold. The oscilloscope displayed the inspiratory V, and each subject was required to inspire to the same peak V for each breath. The subject's inspiratory background R was measured by the interrupter method. Five magnitudes of R loads and no-load were presented randomly 10 times each for a single inspiration after the illumination of a light cue. The subjects were initially given a training trial breathing to the V target. The loads were presented in two trials. The load was estimated using the modified Borg scale. The slope of the log-log relationship between R load magnitude and the ME is a measure of the sensitivity of the subject to R loads. The slope for children with life-threatening asthma was significantly less than that for asthmatic and nonasthmatic children. There were no significant differences in the slope related to race, sex or age in the nonasthmatic children or in the asthmatic children. The reduced sensitivity to increased R loads suggests that these children are at risk of a life-threatening asthmatic attack in part because of an underestimation or delay in the perception of the increased mechanical load that occurs during an asthmatic attack.

Regulation of the manganese superoxide dismutase and inducible nitric oxide synthase gene in rat neuronal and glial cells.

Bidirectional communication occurs between neuroendocrine and immune systems through the action of various cytokines. Responses to various inflammatory mediators include increases in intracellular reactive oxygen species (ROS), notably, superoxide anion (O2-) and nitric oxide (NO.). Neurotoxicity mediated by NO. may result from the reaction of NO. with O2, leading to formation of peroxynitrite (ONOO-). ROS are highly toxic, potentially contributing to extensive neuronal damage. We, therefore, evaluated the effects of a variety of inflammatory mediators on the regulation of mRNA levels for manganese superoxide dismutase (MnSOD) and inducible nitric oxide synthase (iNOS) in primary cultures of rat neuronal and glial cells. To determine age-dependent variation of mRNA expression, we used glial cells derived from newborn, 3-, 21-, and 95-day-old rat brains. Interleukin-1 beta, interferon-gamma (IFN-gamma), bacterial lipopolysaccharide (LPS), and tumor necrosis factor-alpha showed significant induction of MnSOD in both glial and neuronal cells. However, only LPS and IFN-gamma increased iNOS mRNA. These data demonstrate that these two genes are similarly regulated in two cells of the nervous system, further suggesting that the oxidative state of a cell may dictate a neurotoxic or neuroprotective outcome.

Phase relationship between normal human respiration and baroreflex responsiveness.

1. We studied the influences of phase of respiration and breathing frequency upon human sinus node responses to arterial baroreceptor stimulation. 2. Carotid baroreceptors were stimulated with brief (0.6 sec), moderate (30 mmHg) neck suction during early, mid, and late inspiration or expiratin at usual breathing rates, or, during early inspiration and expiration at breathing rates of 3, 6, 12, and 24 breaths/min. 3. Baroreceptor stimuli applied during early and mid inspiration and late expiration provoked only minor sinus node inhibition; stimuli begun during late inspiration and early expiration provoked maximum sinus node inhibition. 4. At breathing rates of 3, 6 and 12 breaths/min, expiratory baroreflex responses were significantly greater than inspiratory responses; at 24 breaths/min, however, inspiratory and expiratory baroreceptor stimuli produced comparable degrees of sinus node inhibition. 5. Our results delineate an important central biological rhythm in normal man: human baroreflex responsiveness oscillates continuously during normal, quiet respiration. The phase shift of baroreflex responsiveness on respiration suggests that this interaction cannot be ascribed simply to gating synchronous with central inspiratory neurone activity. Regularization of heart rate during rapid breathing is associated with loss of the differential inspiratory-expiratory baroreflex responsiveness which is present at usual breathing rates.