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PubMed1990

Transpupillary irradiation of the rabbit retina with the cw-Nd:YAG laser. I. Acute morphologic effects produced using two different pulse forms.

The retinas of six pigmented rabbits (12 eyes) were irradiated with a cw-Nd:YAG laser using two different pulse forms, in conjunction with a constant pulse duration of 200 msec and a retinal focus diameter of 200 microns. The first pulse form (a) was characterized by an initial transient, lasting 15-20 msec, with a peak power twice that of the ensuing plateau phase of 180-185 msec. The second pulse form (b) was almost rectangular in shape. Although the average energies (and powers) for each pulse form were identical, almost 20% of this entity was delivered within the first 20 msec for the first pulse form. Impact lesions were examined at the biomicroscopic, light, and electron microscopic levels, and the characteristic morphologic features described for the cw-mode in general. Comparison of the effects produced using each pulse form revealed a number of differences. At low pulse energies (less than 150 mJ) the rectangular pulse form produced a photocoagulation reaction within the outer sensory retina, but when using the pulse form with the initial transient, this effect was superimposed by a degree of mechanical disruption. Ruptures produced within the elastic component of Bruch's membrane first appeared at lower pulse energies (ie, at 75 mJ, as opposed to 150 mJ for the rectangular pulse form) and were more frequent, and choroidal macrohemorrhaging (observed at pulse energies greater than or equal to 200 mJ) occurred only, when this latter pulse form was employed. Each of these phenomena may be attributed to the higher power and energy densities attained during the initial transient, which has disruptive properties. In order to avoid the risk of severe bleeding, these irradiation parameters should be maintained below approximately 6.4 X 10(3) W/cm2 and approximately 0.13 X 10(3) J/cm2.

Animals↗
PubMed1987

["Saving-effect" of stimulating pulses at low-frequency limbic kindling in cats].

To assess the development of kindling effect induced with low frequency electrical stimulations, we stimulated the lateral amygdala (AM group, 5 cats) and the dorsal hippocampus (HP group, 5 cats) bipolarly, once a day, with 2 mA base to peak, biphasic 1 msec square-wave pulses. In each stimulation we measured the longest inter-pulse interval required for the provocation of epileptic afterdischarge (AD), defined as the pulse-interval threshold; and the number of stimulating pulses required for the provocation of AD at this pulse-interval, defined as the pulse-number threshold. The observed behavioral seizures were classified into 6 stages in both the AM and HP group according to the conventional classification. In the AM group, an increase of the pulse-interval threshold and a decrease of the pulse-number threshold were observed during the kindling process. At the completion of kindling, a generalized convulsion was provoked with 1,200-1,600 msec pulse-intervals, and with 8-12 stimulating pulses. In the HP group an increase of the pulse-interval threshold and a decrease of the pulse-number threshold were observed in the early seizure stages, but not so significantly as the AM group. In the late seizure stages, a decrease of the pulse-interval threshold and an increase of the pulse-number threshold were observed. The observed behavioral stage of seizures in the two groups were similar to that of the conventional high-frequency kindling.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The central oxytocin pulse generator: a pacemaker for luteolysis.

Oxytocin (OT) is released from the neurohypophysis into the jugular vein of sheep in small 1-2 min pulses (ca. 10 pg/ml) in both cyclic and ovariectomized sheep. In intact cycling sheep, additional hour long bursts of OT (up to 200 pg/ml) occur in peripheral blood during luteolysis at intervals of 6 to 9 hrs which appear to regulate large luteolytic pulses of uterine prostaglandin F2a (PGF2a). Since the ovine corpus luteum (CL) also synthesizes OT, experiments were performed to distinguish between the relative contributions of the neurohypophysis and the CL to the large bursts of OT secreted during luteolysis. Two models were used. First, ovariectomized sheep were given exogenous E and/or P by constant infusion to simulate levels during the estrous cycle. Second, in tact cycling sheep, the CL was surgically excised during the luteal phase to exclude the CL as a source of OT and, at the same time, subject the animals to the withdrawal of P. Pulses of OT in jugular vein plasma were determined by RIA or biometry of the uterus. The findings are summarized as follows: In ovariectomized sheep, maintained on low E (0.05 g/hr) to preserve the OT pulse generator, infusion of E (1 microgram, 2 micrograms or 4 micrograms/hr) for 12 to 36 hr, caused a series (4 to 6) of rapid increases in OT pulse frequency each lasting 1 to 2 hrs at intervals of 3 hrs. The time of onset of high frequency pulses was dose-dependent. Withdrawal of 10 day infusions of P (500 micrograms/hr) superimposed on low E (0.05 microgram/hr) also evoked a series of high frequency episodes of OT pulses beginning 24 hrs after P withdrawal. In intact sheep, surgical removal of the CL resulted in a series of high frequency pulses similar in duration and frequency to those following the withdrawal of P in the ovariectomized animal. We conclude that: (1) an increase in E or returning E action causes the OT pulse generator to alter its frequency intermittently thus producing a series of 4 to 6 episodes of high frequency pulses of OT. (2) Similar changes can be evoked by withdrawal of P either by terminating an infusion of P in the presence of E in the ovariectomized sheep or by surgically removing the CL from the ovary in the intact sheep. (3) At the end of the reproductive cycle, the central OT pulse generator appears to act as a pacemaker which, acting on the endometrial OT receptors, triggers a series of pulses of PGF2a from the uterus and hence causes regression of the CL. In the sheep and other ruminants, an intermittent supplemental secretion of OT from the CL, triggered via the central OT pulse generator, may also be required to amplify the luteolytic pulses of PGF2a from the uterus. (4) In addition to the well established interaction of ovarian steroid hormones, and the hypothalamic pituitary system for the initiation of the reproductive cycle via the gonadotrophins, there is now good evidence for an interaction of ovarian steroids and the posterior pituitary for terminating the reproductive cycle.

Animals↗
PubMed1985

Pulse rate, blood pressure and body composition in black adolescents: the Philadelphia Blood Pressure Project.

Patterns of pulse rate, blood pressure (BP), and body size and composition are investigated in a black urban sample of over 600 adolescents (aged 12-17) in Philadelphia as part of the Philadelphia Blood Pressure Project. Supine and seated pulse rates decline after the age of 13 in both males and females, and females have significantly higher pulse rates than males, ranging from 1.6 to 4.7 beats/30 sec higher depending upon chronological age and position. Seated pulse rates are consistently higher than supine in both sexes ranging from 1.3 to 2.9 beats/30 sec depending upon chronological age. Pulse rate and both systolic blood pressure (SBP) and diastolic phase IV blood pressure (DBP) show a positive association throughout adolescence for females (r = 0.16 SBP, r = 0.24 DBP) but not for males (r = -0.06 SBP, r = 0.06 DBP). Females in the highest diastolic IV blood pressure stratum (greater than 85%) maintain higher pulse rates throughout adolescence, while males with the highest DBP have higher pulse rates in early adolescence (ages 12-14) but lower pulse rates in later adolescence (ages 16 and 17). Females with the highest DBP also show consistently higher measures of relative fatness (triceps skinfolds) throughout adolescence. Males with the highest DBP have greater triceps skinfolds in early adolescence and lower triceps in later adolescence, a pattern similar to that shown for pulse rate. For DBP, triceps is significantly and positively associated with pulse rate in the upper DBP percentile group (p less than 0.05). Thus, females with the highest blood pressure during adolescence are characterized by higher pulse rate and greater fatness. Males show this same pattern in early adolescence; whereas, in contrast, the older adolescent males in our sample with the highest DBP are characterized by lower pulse rates, relatively decreased fatness, and increased muscularity. Our findings suggest that, at least in some older black male adolescents, a higher DBP may reflect a decrease in cardiac output as indicated by a lower pulse rate, or an increase in peripheral vascular resistance, possibly associated with relatively decreased fatness and increased muscle mass for size.

Adolescent↗
PubMed1999

Pulse pressure as a risk factor for cardiovascular events in the MRC Mild Hypertension Trial.

OBJECTIVES: The aim of this study was to determine whether pulse pressure is a risk factor for coronary artery disease using data from the MRC trial of treatment of mild hypertension, and whether the effect of anti-hypertensive drug therapy on pulse pressure may be a determinant of outcome in treated patients. METHODS: Logistic regression and Cox regression analyses were used to compare systolic and diastolic blood pressure, pulse pressure and mean blood pressure as predictors of coronary events and stroke in the MRC Mild Hypertension Trial. The effects of anti-hypertensive drug treatment with bendrofluazide and propranolol on pulse pressure were assessed using 1-year follow-up data. Event rates in the placebo-treated group and responses to anti-hypertensive treatment were measured in quartiles of age-adjusted entry pulse pressure. A 'four-corners' analysis was performed, with subjects divided into the upper and lower halves of the distributions of systolic and diastolic blood pressure at entry. RESULTS: Pulse pressure was a stronger predictor of coronary events than systolic, diastolic or mean blood pressure in males by logistic regression. Pulse pressure was similar to systolic pressure as a coronary event predictor on Cox regression. Stroke was predicted most strongly by mean blood pressure. Fatal and non-fatal coronary event rates increased progressively in ascending quartiles of age-adjusted pulse pressure, but there was also a strong correlation with systolic blood pressure. The values of partial logistic regression coefficients in models containing both systolic and diastolic blood pressure also supported a role for pulse pressure in predicting coronary events and for mean blood pressure in predicting stroke. Coronary risk, but not stroke, was inversely related to diastolic blood pressure in the four-corners analysis. In a Cox model, regressions of coronary event probability on systolic blood pressure at entry were significantly and inversely related to diastolic blood pressure categorized in quartiles. Bendrofluazide but not propranolol decreased pulse pressure significantly and was associated with a reduction in cardiovascular events overall, but no definite relationship between the effect of drugs on pulse pressure and specific responses to treatment was seen. CONCLUSION: Pulse pressure is a strong risk factor for coronary events in untreated hypertensive male subjects in the MRC Mild Hypertension Trial, whereas stroke is best predicted by mean blood pressure. Bendrofluazide and propranolol have different effects on pulse pressure which may be related to their relative efficacy in the treatment of hypertension, but this possibility requires further study in more suitable populations.

Analysis of Variance↗
PubMed2000

[Pulse pressure and common carotid arterial wall thickness assessed by ultrasonography].

This study was conducted on a total of 358 normotensive (mean blood pressure < 107 mmHg) inpatients (182 men and 176 women, mean age: 67.8 years) who had no cardiorenal or nutrition disorders that would affect blood pressure, lipid and glucose metabolism and who had not been given depressors or antilipidemic agents during the four years from September 1995 to August 1999. In addition to the known risk factors for atherosclerosis, the effects of pulse pressure and mean blood pressure on sclerotic changes of the carotid arteries were examined. These sclerotic changes were assessed by measuring the thickness of the combined intima-media of the common carotid artery (carotid arterial wall thickness) by ultrasonography (Hitachi EUB-565) and linear probe (7.5 MHz). When the patients were divided into three groups based on pulse pressure (PP1, lower than 51 mmHg: PP2, 51-65 mmHg; PP3, higher than 65 mmHg), the age of the group with higher pulse pressure was significantly higher (p = 0.0011), women more (p = 0.0315). However there were no differences in background factors such as body mass index, Brinkman index, lipid metabolism, uric acid, and glucose metabolism. There was observed a positive correlation between the mean blood pressure and the pulse pressure for both men and women (r = 0.31, p < 0.001, respectively). As for the relation between the pulse pressures and the blood pressure parameters, the systolic blood pressure, pulse pressure and the mean blood pressure were significantly higher in the group with higher pulse pressure (p < 0.001, respectively), but the diastolic blood pressure was significantly lower (p = 0.0275). As for the relation between the pulse pressure and the carotid wall thickness, the groups of both men and women with higher pulse pressures had significantly greater carotid arterial wall thickness (p < 0.001, p = 0.0042, respectively). Logistic regression analysis of the carotid arterial wall thickness (defined as hypertrophic if greater than 1.0 mm) as the object variable and various risk factors including pulse pressure as the explanatory variables revealed that pulse pressure and LDL-C were significant independent contributing factors for men. The age, Brinkman index, T-Chol and HDL-C were significant independent contributing factors for women. For all subjects men, the age, Brinkman index, pulse pressure, TG and LDL-C were significant independent contributing factors. These facts suggest that pulse pressure is an important risk factor for thickening of the carotid arterial wall.

Adult↗
PubMed1994

Rhesus monkey behavior during exposure to high-peak-power 5.62-GHz microwave pulses.

Limits on the exposure to high-peak-power, short-duration microwave pulses have only recently been adopted. Additional data, however, are needed to understand the effects that may be produced by exposure to high-peak-power pulsed microwaves. Four male rhesus monkeys (Macaca mulatta) were trained on an operant task for food pellet reward to investigate the behavioral effects of very high-peak-power 5.62 GHz microwaves. The operant task required monkeys to pull one plastic lever on a variable interval schedule (VI-25 s) and then respond to color signals and pull a second lever to obtain food. The monkeys were conditioned to perform a color discrimination task using one of three colors displayed by a fiber-optic cable. A red signal was the discriminative stimulus for responding on the first lever. A response on the second lever when a green signal was presented (1 s duration) delivered a food pellet. If a response on the second lever was made in the presence of a white signal, a 30-s timeout occurred. While performing the behavioral task, the monkeys were exposed to microwave pulses produced by either a military radar (FPS-26A) operating at 5.62 GHz or the same radar coupled to a Stanford linear energy doubler (SLED) pulse-forming device (ITT-2972) that enhanced peak power by a factor of nine by adding a high power pulse to the radar pulse. The effects of both types of pulses were compared to sham exposure. Peak field power densities tested were 518, 1270, and 2520 W/cm2 for SLED pulses and 56, 128, and 277 W/cm2 for the radar pulses. The microwave pulses (radar or SLED) were delivered at 100 pps (2.8 microseconds radar pulse duration; approximately 50 ns SLED pulse duration) for 20 min and produced averaged whole-body SARs of 2, 4, or 6 W/kg. Compared to sham exposures, significant alterations of lever responding, reaction time, and earned food pellets occurred during microwave exposure at 4 and 6 W/kg but not at 2 W/kg. There were no differences between radar or SLED pulses in producing behavioral effects.

Analysis of Variance↗
PubMed2006

Dependence of calculus retropulsion on pulse duration during Ho: YAG laser lithotripsy.

BACKGROUND AND OBJECTIVES: The purpose of this study was to investigate the effect of optical pulse duration on stone retropulsion during Ho:YAG (lambda = 2.12 microm) laser lithotripsy. STUDY DESIGN/MATERIALS AND METHODS: A clinical Ho:YAG laser with pulse durations was employed to fragment calculus phantoms and to evaluate stone phantom retropulsion. At a given pulse energy, optical pulse durations were divided into two discrete conditions: short pulse (tau(p): 120 to approximately 190 microseconds at FWHM) and long pulse (tau(p): 210 to approximately 350 microseconds at FWHM). Plaster of Paris calculus phantoms were ablated at different energy levels using optical fibers of varying diameters (273, 365, and 550 microm in core size). The dynamics of the recoil action of a calculus phantom was monitored using a high-speed camera; the laser-induced craters were evaluated with optical coherent tomography (OCT). Bubble formation and collapse were recorded with a fast flash photography setup, and acoustic transients were measured with a hydrophone. RESULTS: Shorter pulse durations produced more stone retropulsion than longer pulses at any given pulse energy. Regardless of pulse duration, higher pulse energy and larger fibers resulted in larger ablation volume and retropulsion (P<0.05). For shorter pulse durations, more rapid bubble expansion was observed and higher amplitudes of the collapse pressure wave were measured (P<0.05). CONCLUSION: Less retropulsion and equivalent fragmentation occurred when Ho:YAG pulse duration increased.

Analysis of Variance↗
PubMed2004

Bandwidth-modulated adiabatic RF pulses for uniform selective saturation and inversion.

Radiofrequency (RF) inversion and saturation pulses with extremely high spatial selectivity and uniform profiles are a requirement for numerous MR techniques, such as pulsed arterial spin labeling and outer volume suppression. Adiabatic pulses used for inversion of longitudinal magnetization are ubiquitous, but the superior selectivity of adiabatic full passages has not been widely exploited for saturation because a simple way of calibrating the amplitude of these subadiabatic pulses is lacking. An analytically derived calibration equation is presented, applicable to a large class of pulses including the hyperbolic secant (HS) pulse and allowing the determination of the precise amplitude required to achieve any effective flip angle. The properties of this calibration are examined, and a highly selective and homogeneous HS saturation pulse is demonstrated. Based on this calibration a new class of RF pulses is developed. These bandwidth-modulated adiabatic selective saturation and inversion (BASSI) RF pulses afford optimal amplitude modulation, achieving uniform profiles at any effective flip angle. BASSI pulses are compared to existing gradient modulated adiabatic pulses in simulations and phantom experiments and shown to be superior in terms of selectivity and homogeneity, while requiring less RF energy. An application of BASSI pulses to pulsed arterial spin labeling is shown.

Brain↗
PubMed1994

Responses to pulses and sinusoids in macaque ganglion cells.

The goal of the study was to compare pulse responses with sinusoidal temporal responsivity. The response of macaque ganglion cells was measured to brief luminance and chromatic pulses and to luminance or chromatic sinusoidal modulation. To make both positive and negative lobes of the pulse response visible, responses to pulses of opposite polarity were combined to yield a linearized pulse response. Tests of superposition were used to evaluate the linearized pulse response to different combinations of pulse duration and Weber contrast. A prediction of the pulse response was derived using sinusoidal responsivity functions and Fourier synthesis. For ganglion cells of the parvocellular (PC) pathway, shape and absolute amplitude of linearized pulse responses corresponded well to the predicted responses over a range of pulse durations at 0.5 and 1.0 Weber contrast for both luminance and chromatic modulation. For ganglion cells of the magnocellular (MC) pathway, shape and amplitude of the linearized pulse responses and the predicted responses corresponded when the contrast-duration product was low. This correspondence held for luminance modulation over a thousand-fold range of retinal illuminance. For contrast-duration combinations that produced a more vigorous response, over 100 imp/sec, the linearized pulse responses of MC-pathway cells became larger and time-advanced relative to the linear prediction until saturation became apparent. Incorporation of high Michelson contrast responses in the Fourier synthesis captured the timing but not the amplitude of the linearized pulse response. The data suggest that a mechanism similar to a contrast gain control acts upon MC- but not PC-pathway-cells. The data confirm that use of linear modelling to describe temporal behaviour of retinal ganglion cells is appropriate for small signals.

Animals↗
PubMed2004

The effect of high frequency electric pulses on muscle contractions and antitumor efficiency in vivo for a potential use in clinical electrochemotherapy.

Muscle contractions present the main source of unpleasant sensations for patients undergoing electrochemotherapy. The contractions are a consequence of high voltage pulse delivery. Relatively low repetition frequency of these pulses (1 Hz) results in separate muscle contractions associated with each single pulse that is delivered. It would be possible to reduce the number of unpleasant sensations by increasing the frequency of electric pulses above the frequency of tetanic contraction, provided that the antitumor efficiency of electrochemotherapy remains the same. These assumptions were investigated in the present paper by measuring the muscle torque at different pulse repetition frequencies and at two different pulse amplitudes in rats and studying the antitumor efficiency of electrochemotherapy at different pulse repetition frequencies on tumors in mice. Measurements of muscle torque confirmed that pulse frequencies above the frequency of tetanic contraction (>100 Hz) reduce the number of individual contractions to a single muscle contraction. Regardless of the pulse amplitude, with increasing pulse frequency muscle torque increases up to the frequency of 100 or 200 Hz and then decreases to a value similar to that after application of a 1 Hz pulse train. Electrochemotherapy in vivo with higher repetition frequencies inhibits tumor growth and is efficient at all pulse frequencies examined (1 Hz-5 kHz). These results suggest that there is a considerable potential for clinical use of high frequency pulses in electrochemotherapy.

Animals↗
PubMed2004

Effectiveness of tumor electrochemotherapy as a function of electric pulse strength and duration.

The aim of this study was to evaluate the effectiveness of electrochemotherapy (ECT) as a function of various combinations of pulse strength and duration. C57Bl mice bearing LLC tumors were injected i.p. with bleomycin (BLM) at doses 5 mg/kg in 0.2 ml of physiological saline. Thirty minutes later, tumors were positioned between plate electrodes and were pulsed with eight-square wave electric pulses with an individual pulse strength of 900, 1100, 1300 or 1500 V/cm and duration of 0.1, 0.25, 0.5 or 1 ms. Effectiveness of ECT was estimated by measuring inhibition of tumor growth and by estimating extent of necrosis in histological slices of the treated tumors. At pulse strength of 900 V/cm and duration of 0.1 ms, electrochemotherapy was ineffective. Noticeable inhibition of tumor growth (threshold of ECT) was obtained when pulse duration at this field strength was increased up to 0.25 ms. Further increase of pulse strength and/or duration resulted in progressive enhancement of antitumor effects. Using tumor doubling time (DT) as a criteria, we showed that the same efficacy of ECT could be achieved using various pairs of values for pulse strength and duration. Largest antitumor efficacy of ECT was obtained at pulse strength of 1500 V/cm and duration of 1 ms. These pulse conditions applied alone neither significantly suppressed tumor growth nor induced noticeable side effects of the surrounding tissues. The results of this study thus suggest that the effectiveness of electrochemotherapy can be enhanced (in comparison to widely accepted conditions of electrochemotherapy--8 pulses of 1300 V/cm, 0.1 ms) if 1500-V/cm, 1-ms electric pulses are used. Our study also implicates that other pulse conditions could be found for this enhanced ECT.

Animals↗
PubMed2001

Cell membrane electropermeabilization by symmetrical bipolar rectangular pulses. Part I. Increased efficiency of permeabilization.

The paper presents a comparative study of electropermeabilization of cells in suspension by unipolar and symmetrical bipolar rectangular electric pulses. While the parameters of electropermeabilization by unipolar pulses have been investigated extensively both in cell suspensions and in tissues, studies using bipolar pulses have been rare, partly due to the lack of commercially available bipolar pulse generators with pulse parameters suitable for electropermeabilization. We have developed a high-frequency amplifier and coupled it to a function generator to deliver high-voltage pulses of programmable shapes. With symmetrical bipolar pulses, the pulse amplitude required for the permeabilization of 50% of the cells was found to be approximately 20% lower than with unipolar pulses, while no statistically significant difference was detected between the pulse amplitudes causing the death of 50% of the cells. Bipolar pulses also led to more than 20% increase in the uptake of lucifer yellow. We show that these results have a theoretical background, because bipolar pulses (i) counterbalance the asymmetry of the permeabilized areas at the poles of the cell which is introduced by the resting transmembrane voltage, and (ii) increase the odds of permeabilization of cells having a nonspherical shape or a nonhomogeneous membrane. If similar results are also obtained in tissues, bipolar pulse generators could in due course gain a wide, or even a predominant use in cell membrane electropermeabilization.

Animals↗
PubMed2005

Degradation of alkylbenzene sulfonate surfactants by pulsed ultrasound.

The application of pulsed ultrasound for the degradation of the nonvolatile surfactants sodium 4-octylbenzene sulfonate (OBS) and sodium dodecylbenzenesulfonate (DBS) was investigated at a frequency of 354 kHz. By comparing the degradation rate constants with those of continuous wave (CW) ultrasound, observed pulse enhancements were found to be dependent on the pulse length, pulse ratio, initial concentration, and surface activity of the surfactants. For a pulse length of 100 ms and a pulse ratio of 1:1 (equal on/off times), the degradation rate constant of 1 mM OBS was nearly twice the value for CW. Furthermore, the degradation rate constant for 1 mM DBS increased significantly when sonicated under a pulse length of 100 ms and a pulse on/off ratio of 1:50. However, the degradation rate of 0.1 mM OBS increased by only 30% with a 100 ms pulse length and pulse ratio of 1:1 as compared to CW, indicating concentration dependence. The enhanced degradation of surfactants by pulsed ultrasound was attributed to the accumulation of surfactants on cavitation bubble surfaces. In addition, as compared to shorter pulse intervals, longer pulse intervals enhanced DBS degradation, indicating that DBS, a more surface active compound, accumulated and equilibrated with the bubble interface more slowly.

Journal Article↗
PubMedDate not supplied

Reliability of conventional and new pulse oximetry in neonatal patients.

OBJECTIVES: Pulse oximetry is widely used in the NICU, but clinicians often distrust the displayed values during patient motion, i.e., questionable oxygen saturation (SpO(2)) and pulse rate (PR) values. Masimo Corporation (Irvine, CA) has developed pulse oximetry with claims of resistance to sources of interference. To test this premise, we compared the performance of the Masimo SET pulse oximeter to a conventional device, Nellcor N-200, and then with three other new-generation pulse oximeters, Nellcor N-395, Novametrix MARS, and Philips Viridia 24C. STUDY DESIGN: We studied 26 nonsedated NICU infants who were on supplemental oxygen and/or mechanical ventilation. ECG heart rate (HR) from a bedside monitor and SpO(2) and PR from the two pulse oximeters were captured by a PC for a total of 156 hours. The ECG HR and pulse oximeter spectral waveform were analyzed at alarms for hypoxemia (SpO(2)< or = 85%) and/or bradycardia (HR< or = 80 bpm). We then compared the performance of the Masimo SET to three other new-generation pulse oximeters, Agilent Viridia 24C, Nellcor N-395, and Novametrix MARS, in a similar population of seven infants for a total of 28 hours. We added to the test criteria the ability of the various pulse oximeters to track acute changes in HR. RESULTS: Compared with Nellcor, Masimo SET had 86% fewer false alarms, which also were shorter in duration, resulting in 92% less total alarm time. Masimo SET also identified nearly all bradycardias versus 14% for the Nellcor. Compared with the new-generation pulse oximeters, false desaturations, data drop-outs, and false bradycardias were lowest for Masimo SET, as was the capture of true desaturations and bradycardias. Notably, the new-generation devices differed greatly in their ability to detect changes in HR (i.e., the frequency of frozen PR during times of ECG HR change was 0, 6, 11, and 46 for Masimo, Nellcor, Philips, and Novametrix, respectively). CONCLUSIONS: Masimo SET pulse oximetry recorded markedly fewer false SpO(2) and PR alarms and identified more true hypoxic and bradycardic events than either conventional or other new-generation pulse oximeters. Masimo SET also most closely reflected the ECG rate irrespective of accelerations or decelerations in HR. SPECULATION: Routine use of Masimo SET pulse oximetry in the NICU could improve clinician confidence in the parameter leading to more judicious titration of oxygen with possible reductions in hypoxic (e.g., pulmonary hypertension) and hyperoxic (e.g., retinopathy of prematurity) pathology. Additionally, a more trustworthy technology should equate with fewer confirmatory arterial blood gas analyses (less blood loss), and faster weaning from the mechanical ventilation (less chronic lung disease).

Heart Rate↗
PubMed1998

Itraconazole pulse therapy is effective in the treatment of Majocchi's granuloma: a clinical and pharmacokinetic evaluation and implications for possible effectiveness in tinea capitis.

Majocchi's granuloma is a folliculitic and perifolliculitic dermatophyte infection of the dermis, a site that is not generally colonized by fungi in immunocompetent individuals. Topical agents are usually ineffective therapeutically because of the deep location of the infection. The objective of this study was to determine the effectiveness of oral itraconazole. We also examined the pharmacokinetics of the drug in scalp hair during pulse therapy. This information would then be useful in determining the efficacy of itraconazole administered by means of intermittent pulse dosing in the treatment of tinea capitis. Seven patients (age range 25-75 years) were treated up to three times with itraconazole pulse therapy, 200 mg twice daily for 1 week, with 2 weeks off between pulses. Samples of scalp hair and plasma were also obtained to determine the pharmacokinetics of the drug at these two sites. All seven patients responded to therapy, clinical and mycological cure being achieved after one pulse (one patient), two pulses (three patients), or three pulses (three patients, each with toenail onychomycosis); none relapsed over a 6-18-month follow-up period. In all six patients who received two or more pulses of itraconazole, almost complete cure was observed before the second pulse, with full resolution within 2 weeks of its completion. Itraconazole was also detected in the hair after 1 week, and at concentrations 2.6-fold and 3.4-fold higher, respectively, after the second and third pulses. After the discontinuation of therapy, itraconazole was then detectable in the hair for 9 months, at least in a female patient who did not have her hair cut. Two pulses of oral itraconazole therapy thus appear to be effective in the treatment of Majocchi's granuloma, and it is possible that one pulse may be sufficient in some patients. These data suggest that itraconazole pulse therapy should be effective in the treatment of tinea capitis.

Adult↗
PubMed2002

Risk evaluation and therapeutical implications of pulse pressure in primary arterial hypertension.

SUMMARY: Analysis of the results raised in the Framingham and the MRFIT study have clearly shown that increased pulse pressure is an independent cardiovascular risk factor. This is valid for all age groups and both sexes. The risk increases with pulse pressures over 60 - 65 mmHg for office blood pressure and 53 mmHg for 24-h-mean of ambulatory blood pressure. Pulse pressure is strongly correlated with systolic blood pressure and will be highest in case of isolated systolic hypertension. Urinary albumin excretion and left ventricular hypertrophy are closely associated with pulse pressure. With elevated pulse pressure cardiovascular risk is increased 2- to 4-fold in relation to age and endpoint. The risk of myocardial infarction is raised more if pulse pressure is associated with low mean arterial blood pressure while risk of stroke is increased with wide pulse pressure and high mean arterial pressure. The risk of pulse pressure can be seen in normotensives and in early pregnancy. Therapeutic management of pulse pressure will be similar to that of systolic blood pressure, since normalization of systolic blood pressure will also lower or normalize pulse pressure. Results of preliminary studies suggest that diuretics are superior to other drugs in decreasing pulse pressure. An increase of pulse pressure during therapy should be avoided since each 10 mmHg increase in pulse pressure will raise the risk of stroke and myocardial infarction about 24 % and 32 %.

Adult↗
PubMed1998

Response of single species biofilms and microcosm dental plaques to pulsing with chlorhexidine.

The aim of this study was to determine the effect of pulsing chlorhexidine gluconate, at concentrations commonly used in mouthwashes, on Streptococcus sanguis biofilms and microcosm dental plaques in vitro. Biofilms were grown on bovine enamel and nutrients were supplied in the form of artificial saliva. Pulsing experiments were carried out on steady-state biofilms using 0.05 or 0.2% chlorhexidine solutions delivered twice daily for 1 min. In a separate study, the enamel discs on which the biofilms were formed were pre-treated with chlorhexidine and pulsed directly after inoculation and then at regular intervals. With both concentrations of chlorhexidine used, a c.2 log10 reduction in the viable counts of S. sanguis was achieved with the initial pulse, but as pulsing continued, the bacterial population recovered, albeit not to the previous level. A c.1 log10 reduction in the total viable counts of the microcosm plaques was seen after the first pulse with 0.2% chlorhexidine. The total count then recovered rapidly and, after the fifth pulse, the total viable counts were not significantly different from those before pulsing. The total counts then remained at a similar level throughout the course of the experimental runs. Pre-treatment of the enamel discs with 0.2% chlorhexidine before inoculation produced viable counts of c.10(5) cfu/mm2, a 1 log10 reduction compared with untreated discs. After pulsing with 0.2% chlorhexidine at 8 h, a 3 log10 reduction was seen in the total aerobic and anaerobic counts, but again the viable counts subsequently increased despite twice-daily chlorhexidine pulsing. Regardless of the nature of the biofilm, pulsing initially achieved substantial kills, but the viability of the biofilms subsequently increased despite continued pulsing. Chlorhexidine was effective at reducing the viability of microcosm plaques when it was applied to the substratum before exposure to bacteria and subsequently pulsed on to the biofilms.

Animals↗