Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pulse”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources
PubMed2005

Higher brachial-ankle pulse wave velocity is associated with more advanced carotid atherosclerosis in end-stage renal disease.

Brachial-ankle pulse wave velocity is a new measure of arterial stiffness. We examined whether higher brachial-ankle pulse wave velocity is associated with more advanced carotid atherosclerosis and left ventricular hypertrophy in patients with end-stage renal disease, and whether this effect would be mediated by the influence of wave reflection on central arterial pressure. In 68 patients with end stage renal disease, we examined blood pressures, brachial-ankle pulse wave velocity and the augmentation index of the left common carotid artery, a measure of the impact of wave reflection on the systolic peak in central arteries. The degree of carotid atherosclerosis was quantified by a plaque score and maximum intimal-medial thickness. Echocardiography was used to determine the left ventricular mass index. In simple regression analysis, brachial-ankle pulse wave velocity was correlated with both plaque score and maximum intimal-medial thickness (r = 0.420, p < 0.001 and r = 0.452, p < 0.0005, respectively) but not with left ventricular mass index. Multiple regression analysis was performed with the plaque score or maximum intimal-medial thickness as the dependent variable and brachial-ankle pulse wave velocity and known clinical risk factors as the independent variables. The brachial-ankle pulse wave velocity was an independent risk factor for both plaque score (beta = 0.006, p = 0.004) and maximum intimal-medial thickness (beta = 0.008, p = 0.04). Independent risk factors for left ventricular mass index were left ventricular diastolic dimension (beta = 3.509, p = 0.000007) and augmentation index (beta = 0.580, p = 0.04). The brachial-ankle pulse wave velocity was unrelated to augmentation index in patients with end stage renal disease. In conclusion, higher brachial-ankle pulse wave velocity was found to be a risk factor for carotid atherosclerosis in patients with end-stage renal disease; this effect was independent of the influence of wave reflection on central arterial pressure. The brachial-ankle pulse wave velocity was unrelated to left ventricular structure.

Adult↗
PubMed2004

Narrow-linewidth megahertz-rate pulse-burst laser for high-speed flow diagnostics.

A second-generation pulse-burst laser system for high-speed flow diagnostics is described in detail. The laser can produce a burst of high-energy pulses (of the order of hundreds of millijoules per pulse) with individual pulse durations of less than 10 ns and pulse separations as short as 1 micros. A key improvement is the addition of a phase-conjugate mirror, which effectively isolates the high-intensity, short-duration pulses from the low-intensity, long-duration background illumination. It allows for more-efficient amplification and harmonic generation, with efficiencies exceeding 50% for second-harmonic and 40% for third-harmonic generation. Characteristics of the laser system, including gain narrowing, pulse-burst energy distribution, pulse narrowing, and overall pulse-burst energy, are described. In addition, the applicability of the laser for spectroscopic-based flow diagnostics is demonstrated through the presentation of megahertz-rate planar Doppler velocimetry results.

Journal Article↗
PubMed1980

Two-pulse discrimination and rapid light adaptation: complex effects on temporal resolution and a new visual temporal illusion.

Temporal resolution during rapid light adaptation was studied using a suprathreshold two-pulse discrimination paradigm with stimulus conditions modeled after the classic increment threshold experiments of B. H. Crawford. The two-pulse stimulus (1 degree diam, two 20-ms pulses separated by 40 ms) was presented before, during, and after a 6 degree diam, 500 ms background conditioning field, and discriminability was measured as d' using signal detection methods. Discriminability is depressed at background field onset and offset, but increases during the exposure time of the background. Immediately following background offset, two-pulse discriminability is dramatically enhanced: two pulses are discriminated from one pulse with a d' of 4 or more. When the two-pulse stimulus follows background offset by 80 to 250 ms, a novel temporal illusion occurs: a single pulse consistently appears as a double pulse. Several hypotheses for understanding these results are discussed.

Adaptation, Ocular↗
PubMed2006

Comparison of merocyanine 540-mediated photodynamic action on leukemia cells between pulsed and continuous wave light sources.

Whether a pulsed laser is superior to a continuous wave (CW) light source in photodynamic therapy (PDT) of cancer is still unclear and contradictory in the literature. Although photosaturation of a sensitizer and oxygen depletion in tumor have been considered to be involved during pulsed laser irradiation, there is a lack of experimental data. In the present work several parameters such as the amount of merocyanine 540 (MC540) in cells, the oxygen concentration in cells, and the amount of photos reaching cells during pulsed laser irradiation, were studied to compare the MC540-mediated PDT effects of a pulsed laser and a CW light source on murine myeloid WEH-3B (JCS) cells in vitro. The results showed that the pulsed laser was less effective at cell inactivation than the CW light under the same irradiation dose. However, when the energy of the pulsed laser was reduced from 0.25 to 0.06 mJ/cm2 while keeping the total irradiation dose unchanged, the photoinactivation of cells was increased significantly. Based on the measurements and calculations for the present experimental conditions, each cell has about 108 MC540 molecules bound (5 microg/ml MC540 for 1 hr) and receives about 109 photos from 0.25 mJ/cm2 of the pulsed laser. The results indicate that the photosaturation of MC540 occurs in the present conditions due to the fact that the photons received by one cell in one laser pulse were much more than the numbers of MC540 molecules bound to one cell. Thus, the photosaturation of the photosensitizer is one of the reasons to explain the different efficiency in cell inactivation between the pulsed laser and CW light.

Animals↗
PubMed2006

Acute and chronic effects of pulse exposure of Daphnia magna to dimethoate and pirimicarb.

Short-term (<48 h) and long-term (21 d) effects of dimethoate and pirimicarb were studied in Daphnia magna exposed to pulses of 0.5 to 8 h in duration. During a 21-d postexposure observation period, the following parameters were monitored: Mortality, mobility, day for first offspring, animal size, weight of offspring and adults, and number of offspring produced. In general, animals exposed to a single pulse of dimethoate or pirimicarb regained mobility after 24 to 48 h in clean media. Animals exposed to repeated pulses of dimethoate did not recover mobility during a 48-h postexposure observation period, and mortality was significantly increased. Animals exposed to two pulses of pirimicarb showed less recovery of mobility compared with those exposed to one pulse. Exposure of D. magna to 30 mg/L of dimethoate or 100 microg/L of pirimicarb for 2 to 6 h resulted in a significant reduction in the number of offspring and in the average weight of offspring. The average body length was reduced after pulse exposure to 30 mg/L of dimethoate for 3 h or 70 microg/L of pirimicarb for 4 h, and these exposure concentrations caused a delay in the day for first offspring at exposure durations of 2 to 6 h. The most important new findings in the present study are that short-term (<4 h) pulse exposure of neonates to acetylcholinesterase-inhibiting pesticides caused reproductive damage in D. magna and that repeated-pulse exposure significantly increased mortality in animals that apparently had recovered after a single-pulse exposure.

Aging↗
PubMed1998

Should one use electrocardiographic or Finapres-derived pulse intervals for calculation of cardiac baroreceptor sensitivity?

BACKGROUND: Cardiac baroreceptor sensitivity (BRS) can now be calculated non-invasively with the advent of new beat-to-beat blood pressure monitors and simulatneous surface electrocardiographic recording. However, it is not known whether BRS values calculated using a pulse interval obtained from the pulse wave are different from those using the electrocardiographic trace. This is important with the advent of new portable monitors (e.g. Portapres), which do not record a simultaneous electrocardiographic trace. OBJECTIVE: To determine whether pulse interval derivations from pulse wave data and electrocardiographic data are comparable.METHODS: Twenty healthy volunteers (10 men) aged 48 +/- 17 years with mean blood pressure 134 +/- 13/77 +/- 7 mmHg were examined. Supine beat-to-beat arterial blood pressure (measured using a Finapres 2300 device from Ohmeda) and surface electrocardiographic readings were recorded and spectral analysis, using fast Fourier transformation (FFT), and sequence analysis used to calculate BRS. Pulse interval was marked using both electrocardiographic and blood pressure traces and we compared the resulting variability of pulse interval and BRS values obtained using the two methodologies. RESULTS: There was good agreement between the two methods for pulse interval power in the low-frequency bandwidth and for BRS sequence analysis, especially for 'down' sequences, (limits of agreement -26.3 to 77.1 ms2 and -1.6 to 2.7 ms/mmHg, respectively). However, in the high frequency bandwidth (0.15-0.35 Hz) and for the combined BRS, the agreement was less good (-69 to 153.8 ms2 and -0.3 to 1.5 ms/mmHg). Overall differences between methods were smaller for BRS calculated in the low frequency rather than high-frequency band, but only in the low-frequency band was the difference positively correlated to mean BRS values. CONCLUSION: Cardiac BRS values calculated using pulse intervals derived from the pulse wave are different from those on the surface electrocardiographic trace, the greatest differences occurring in BRS derived from the high-frequency bandwidth. However, these differences are small, especially in the low-frequency band at lower mean BRS values, and should not discourage use of these newer methods of BRS measurement that do not involve an electrocardiographic recording.

Journal Article↗
PubMed1999

Thresholds for visible lesions in the primate eye produced by ultrashort near-infrared laser pulses.

PURPOSE: To evaluate the effects of near-infrared (near-IR) ultrashort laser pulses on the retinas of rhesus monkey eyes and to perform threshold measurements for minimum visible lesions (MVLs) at pulse widths ranging from nanoseconds to femtoseconds. METHODS: Near-infrared single laser pulses were placed within the macular area of live rhesus monkey eyes for five different pulse widths (7 nsec; 80, 20, and 1 psec; and 150 fsec). One visible wavelength of 530 nm at 100 fsec was also included in the study. Visible lesion thresholds (MVL-ED50) were determined 1 hour and 24 hours after exposure. Fluorescein angiography thresholds (FAVL-ED50) were also determined using a probit analysis of the dosage. Thresholds were calculated as that dosage causing a 50% probability for damage, and the fiducial limits were calculated at the 95% confidence level. RESULTS: For all pulse widths, the 24-hour MVL-ED50 was lower than the 1-hour MVL-ED50, and they both decreased with decreasing pulse width. Thresholds at the 1-hour reading decreased from 28.7 microJ at 7 nsec to 1.8 microJ at 150 fsec, whereas thresholds at 24 hours decreased from 19.1 microJ at 7 nsec to 1.0 microJ at 150 fsec. The doubled 1060-nm wavelength of the 530-nm threshold decreased from 0.36 to 0.16 microJ after 24 hours. FAVL-ED50s were much higher than MVL-ED50s, showing that FA was not as sensitive in determining damage levels. CONCLUSIONS: Laser pulse widths less than 1 nsec in the near-IR are capable of producing visible lesions in rhesus monkey eyes with pulse energies between 5 and 1 microJ. Also, the near-IR thresholds for these pulse widths are much higher than for the visible wavelengths. As with visible wavelengths, FA is not as sensitive in determining threshold levels as is visually observing the retina through a fundus camera.

Animals↗
PubMed2000

Effect of exogenous LH pulses on the fate of the first dominant follicle in postpartum beef cows nursing calves.

Prolonged postpartum anoestrus in beef cows is due to failure of early dominant follicles to ovulate. It is hypothesized that this failure to ovulate is due to inadequate LH pulse frequency. The objective of this study was to determine whether administration of hourly LH pulses would cause the first dominant follicle to ovulate. In Expt 1, 16 cows received either saline (n = 8) or porcine LH (pLH; 50 micrograms h-1; n = 8) as hourly pulses for 3-5 days from the second day of dominance of the first dominant follicle (day 0). In Expt 2, 21 cows received either saline (n = 7), or 50 micrograms pLH (n = 7) or 100 micrograms pLH (n = 7) as hourly pulses for 3 days. Appropriate ovarian scanning and assays of blood samples were carried out. In Expt 1, the number of dominant follicles that underwent atresia was not affected by increasing the number of LH pulses, but the duration of dominance (days) of the first and second dominant follicles and maximum size (mm) of the second dominant follicle were increased (P < 0.05). Oestradiol concentrations were higher (P < 0.05) in cows given hourly pLH pulses (3.1 +/- 1.2 pg ml-1) compared with controls (1.2 +/- 0.2 pg ml-1). Four of eight treated cows had an anovulatory LH surge. The number of follicle waves to first ovulation was not different (P < 0.05) between control (4.6 +/- 0.9) and pLH treated cows (3.9 +/- 0.5). In Expt 2, four of seven cows given pulses of 100 micrograms pLH h-1 ovulated the first dominant follicle, and the interval from calving to first ovulation was decreased (P < 0.05). In the remaining three cows, the duration of dominance of the first dominant follicle was increased (P < 0.005), the maximum size of the first dominant follicle was greater (P < 0.05), and the interval (days) from the start of infusion to new wave emergence was greater (P < 0.05) compared with cows that failed to ovulate in either the 50 micrograms pLH h-1 or control treatments. In conclusion, hourly pulses of pLH from day 1 after dominance of the first dominant follicle in postpartum beef cows can either prolong dominance or induce it to ovulate. This finding supports the hypothesis that LH pulse frequency is a key determinant of the fate of the dominant follicle in the early postpartum period.

Analysis of Variance↗
PubMed2001

[Electric pulse mediated high efficient gene transfer].

OBJECTIVE: To study gene transfer mediated by electric pulse and optimize the parameters of electric pulse in vivo. METHODS: 10 micrograms plasmid pcD2/LacZ was injected into the quadriceps of 220 Kunming mice. One to two minutes after the DNA injection electric pulse with different parameters was given to the injection site. Three days after, activity of beta-galactosidase was measured, and the expression of Laz2 gene in muscle was determined by histochemical staining. RESULTS: The activity of beta-galactosidase in electric pulse group (131.6 U/mg +/- 86.6 U/mg protein) was 30 fold higher than that in direct injection group (4.9 U/mg +/- 1.0 U/mg protein) (P < 0.05). Histochemical analysis of muscles injected with a LacZ expression plasmid also showed that in vivo electric pulse increased both the number of positively stained muscle fibers and the density of staining. When the electric pulse was with the parameters of 200 V/cm, 40 ms, 6 pulses and 1HZ, maximal gene expression was achieved. CONCLUSION: Electric pulse, with optimal parameters, increases gene expression. Electric pulse makes much more gene expression than mere intramuscular DNA injection.

Animals↗
PubMed2002

The effects of motion artifact and low perfusion on the performance of a new generation of pulse oximeters in volunteers undergoing hypoxemia.

INTRODUCTION: Motion artifact and low perfusion often lead to faulty or absent pulse oximetry readings in clinical practice. OBJECTIVE: Determine the impact of motion artifact and low perfusion on newly introduced pulse oximetry technologies during hypoxemic episodes in healthy volunteers. METHODS: Five different pulse oximeters from 4 manufacturers (the Datex Ohmeda 3900P; the Agilent; the Nellcor N-3000; the Nellcor N-395; and the Schiller OX-1, which is the European version of the Ivy SatGuard 2000 with Masimo SET) were compared with respect to their ability (separated or in combination) to provide accurate readings in the presence of motion artifact and low perfusion. Four of these oximeters represent the latest available oximetry technology, and one (the N-3000) represents a previous generation of oximeters. Oxygen saturation values (S(pO(2))) and pulse rate from the oximeters were recorded during episodes of induced hypoxemia in 10 healthy volunteers. Standardized and repeatable motion artifacts were generated by a motion machine and by having the test subject perform tapping and scratching motions. Perfusion to the finger was reduced by an inflatable balloon impinging on the brachial artery. The pulse oximetry readings from the test oximeters were compared to readings from control pulse oximeters on the unperturbed reference hand. The pulse rates from the test oximeters were compared to the electrocardiographically-measured heart rate. RESULTS: The frequency of faulty readings was increased by increasing motion interference and decreasing perfusion. The S(pO(2)) deviation was within +/- 3% of the reference reading > 95% of the time for all instruments during the control desaturation period in the absence of motion and with normal perfusion. With the combination of motion and low perfusion, the S(pO(2)) error was within +/- 3% less than 62% of the time for all oximeters tested. A significant difference in the frequency of large S(pO(2)) errors was observed only in the direct comparison of the N-395 and N-3000. The N-395 exhibited less frequent S(pO(2)) error exceeding 6% of S(pO(2)) in the combination of the most challenging situations (motion and motion with reduced perfusion). In the same situation the Datex-Ohmeda 3900P and Nellcor N-3000 showed significantly higher pulse rate errors than the other devices (Datex-Ohmeda 3900P 53% of the time and N-3000 37% of the time). CONCLUSIONS: The established model of creating motion artifact and low perfusion is capable of simulating a hierarchy of severe clinical situations. With solely motion or solely reduced perfusion the percentage of errors exceeding +/- 3% of S(pO(2)) increased by 20% and 10%, respectively, compared to the control period. Simultaneous presence of motion and reduced perfusion leads to a relative incidence of > 35% of errors > 3% of S(pO(2)) for the various oximeters. In this situation the N-3000 and the Datex-Ohmeda 3900P exhibited differences between estimated pulse rate and electrocardiographically-measured heart rate > 25 beats/min > 37% of the time.

Adult↗
PubMed2003

Horizontal sub-surface flow constructed wetland with pulsing water level.

A constructed wetland with horizontal sub-surface flow at Dolni Mesto (Czech Republic) was put into operation in 1999 and treats municipal wastewater from 522 PE. The total area of vegetated beds of 2,646 m2 is divided into two parallel sections of equal size, each with two beds in series. Between two periods of water discharge there is no outflow from the bed. During the period of September 1999-September 2000 one bed was operated with a pulsing water level while the other one was not pulsing, i.e., was operated as regular sub-surface flow in order to evaluate the effect of pulsing on treatment efficiency, especially on removal of NH4-N. Between September 1999 and February 2000 the pulse was 8 cm, for the rest of the experimental period the pulse was 15 cm. The results indicate a positive effect of pulsing on removal of BOD5 (annual average of 53%), COD (30%) and NH4-N (27%) as compared to non-pulsing beds. For SS, a decrease in removal effect by 30% was observed. This is probably due to the higher outflow velocity of discharged water from pulsing beds which can flush out settled particles. The results also indicate that a pulsing level of 15 cm was more efficient than 8 cm.

Ammonia↗
PubMed2005

Vaccination with dendritic cells pulsed with apoptotic cells elicits effective antitumor immunity in murine hepatoma models.

Dendritic cell (DC)-based vaccine is a developing strategy to treat cancer including hepatoma. We evaluated the antitumor efficacy of vaccination with DCs pulsed with apoptotic cells, as compared to vaccination with DCs pulsed with cell lysates, in murine hepatoma models. Murine hepatoma cells, Hepa1-6, MH134 and BNL1ME.A.7R.1, and their syngeneic mice, C57BL/6, C3H/HeN and BALB/c, respectively, were used in the study. Protective and therapeutic antitumor effects of vaccination with bone marrow-derived DCs pulsed with irradiation or sulindac-induced apoptotic cells or cell lysates were analyzed. Immature DCs efficiently phagocytosed apoptotic cells and increased expression of CD86, a cell surface maturation marker. Vaccination with apoptotic cell-pulsed, but not cell lysate-pulsed, DCs promoted significant protective immunity against parental hepatoma in vivo. Spleen cells from mice vaccinated with apoptotic cell-pulsed DCs showed higher cytolytic activity and contained higher number of IFN-gamma producing cells against parental hepatoma cells than those from mice vaccinated with cell lysate-pulsed DCs in vitro. Polyriboinosinic polyribocytidylic acid [poly (I:C)], double strand RNA, further enhanced CD86 expression and the therapeutic efficacy of vaccination with DCs pulsed with apoptotic cells for pre-established hepatoma. These results suggest that vaccination with DCs pulsed with apoptotic cells and treated with poly (I:C) appears to be a promising approach as a new therapeutic means for hepatoma.

Animals↗
PubMed2005

[Phenotype and function of myeloid dendritic cells pulsed with hepatitis B virus antigens in patients with HBV-associated hepatocellular carcinoma].

OBJECTIVE: To investigate the characteristics of phenotype and function of myeloid dendritic cells (mDCs) pulsed with HBV antigens derived from HBV-associated hepatocellular carcinoma (HCC) patients. METHODS: Peripheral blood mononuclear cells (PBMCs) were collected, using blood cell separator, from 21 primary HCC patients and 4 healthy donors. mDCs were propagated in serum-free AIM-V medium in the presence of cytokine cocktail, and pulsed with HBcAg or HBsAg. After 9 days' incubation, the phenotypic patterns of mDC were characterized by flow cytometry and the levels of IL-10 and IL-12 produced by mDCs were analyzed by ELISA. Autologous T cells proliferation stimulated by mDC was tested by non-radioactive cell proliferation assay kit. RESULTS: The expression rates of CD80, CD86, CD40, and HLA-DR in the mDCs pulsed with HBcAg were 55% +/- 26%, 80% +/- 13%, 70% +/- 13% and 73% +/- 24% respectively, significantly higher than those of the control group (29% +/- 25%, 35% +/- 18%, 44% +/- 26% and 45% +/- 23% respectively, all P < 0.05). Among the expression rates of surface molecules of the mDCs pulsed with HBsAg only the expression rate of HLA-DR was significantly higher than that of the un-pulsed mDCs (63% +/- 15% vs 45% +/- 23%, P < 0.05). T cell proliferation assay revealed an impaired allostimulatory capacity of mDCs in HCC and the stimulatory capacity of the mDCs pulsed with HBcAg to induce proliferation of autologous T cells was more powerful than that pulsed with HBsAg (P < 0.05). The levels of IL-10 and IL-12 produced by the mDCs pulsed with HBsAg were (35 pg/ml +/- 9 pg/ml and 135 pg/ml +/- 63 pg/ml respectively, both significantly lower than those pulsed with HBcAg (236 pg/ml +/- 95 pg/ml and 733 pg/ml +/- 212 pg/ml respectively, both P < 0.05). CONCLUSION: Pulsation of mDCs in vitro by HBcAg or HBsAg enhance the expression of CD80, CD86, CD40, and HLA-DR, and increase the ability of mDCs to stimulate the proliferation of autologous T lymphocytes.

Adult↗
PubMedDate not supplied

Pulse oximetry: evaluation of accuracy during outpatient general anesthesia for oral surgery.

Pulse oximetry has been shown to be accurate under steady state conditions. In this study, the accuracy of four pulse oximeters are evaluated and compared during outpatient general anesthesia for third molar extractions. The oximeters evaluated are the Nellcor N-100, the Ohmeda 3700, the Novametrix model 500, and the Bird 4400 portable pulse oximeter.Ultralight general anesthesia for oral surgery presents a unique challenge for respiratory monitoring in that patients are often not intubated and commonly experience periods of hyper- and hypoventilation. Airway obstruction, apnea, and laryngospasm may occur easily and patients often vocalize and move during surgery. Because hypoxemia is the primary cause of morbidity and mortality during anesthesia, an accurate, continuous, and noninvasive monitor of oxygenation is critical to risk management.Twenty ASA class I and II patients underwent outpatient general anesthesia for third molar removal using nitrous oxide-oxygen, midazolam, fentanyl, and methohexital. Arterial blood samples were obtained at five-minute intervals during anesthesia, as well as any time a desaturation of >5% occurred, for measurement of arterial SaO(2) with an IL282 CO-Oximeter. These values were compared with simultaneously recorded saturations observed for each pulse oximeter. A total of 122 arterial samples were obtained over a range of PaO(2) from 52-323 mm Hg and observed saturations of 70-100%.The Bird 4400 portable pulse oximeter proved to be the most accurate and reliably predicted arterial saturation under these conditions (y = 1.03x - 2.8, r = 0.85). The Novametrix model 500 pulse oximeter also demonstrated a high degree of accuracy by linear regression analysis, but displayed the lowest correlation coefficient (spread of data points) overall (y = 0.97x + 2.8, r = 0.80.) The Nellcor N-100 pulse oximeter also proved to be highly accurate. (y = 1.05x - 4.1, r = 0.84.) In contrast, regression analysis of the observed saturations obtained with the Ohmeda 3700 pulse oximeter revealed that this unit significantly underestimated arterial saturation (y = 1.20x - 19.6, r = 0.83.)This study demonstrates that despite the rigorous conditions imposed by outpatient general anesthesia for oral surgery, three of the pulse oximeters tested were linearly accurate in predicting arterial oxyhemoglobin saturation over the range of 70-100%. The Ohmeda 3700 was found to significantly underestimate arterial saturation.

Ambulatory Care↗
PubMed1988

[Noninvasive determination of oxygen saturation using pulse oximetry in pediatric cardiology].

Pulse oximetry is a relatively new noninvasive method to measure arterial oxygen saturation (SO2). We evaluated the reliability of a pulse oximeter (N-100, Nellcor/Drger, Lübeck) in single and continuous measurements of SO2. During cardiac catheterisation we compared pulse oximeter (puls.SO2) measurements to those in simultaneously taken arterial samples (art.SO2), and obtained 203 pair measurements in 85 patients, mostly newborns and infants; in 20 of them before and during the breathing of oxygen through a mask. We also have 67 pair measurements of capillary blood samples (kap.SO2) and puls.SO2. Continuous measurements with the pulse oximeter were carried out in 17 patients for up to 116 h. Our main results are: 1. In the puls.SO2 range of 66% to 100% the measurements with the pulse oximeter were accurate (r = 0.97, Syx = 2.1). Below 66% the puls.SO2 values were on average much higher than the art.SO2 values, with an increased variance. Intraindividual oxygenation changes before and during the breathing of oxygen were accurately measured. 2. Pulse oximetry is much more informative than kap.SO2 measurements, because its information about the SO2 before blood sampling (= resting value) and following SO2 changes during the painful procedure (= stress values). 3. Continuous measurements with the pulse oximeter are very simple and very reliable and are not associated with skin injury. Because the pulse oximeters responses rapid to oxygenation changes and does not need calibration it is very valuable in the assessment of therapeutic procedures in patients with cyanotic heart disease. We conclude that the pulse oximeter is a very important new diagnostic tool in pediatric cardiology.

Blood Gas Monitoring, Transcutaneous↗
PubMedDate not supplied

Methylprednisolone pulses and urine electrolyte excretion.

The mineralocorticoid activity of methylprednisolone pulses was assessed by measurement of urine electrolyte excretion prior to and during alternate day pulsing in patients with skin or joint disease. Two groups were studied: the first receiving pulses, but no other steroid; the second having taken oral prednisolone prior to and during pulsing. Urine sodium excretion in 24 hr urine specimens from both groups was suppressed, with no rebound between pulses, but a gradual "escape" occurred from the effects of continued pulsing. Four hour urine collections demonstrated suppression of urinary sodium excretion for up to 32 hr after pulsing with gradual recovery. The peak recovery in sodium excretion coincided with the subsequent pulse and was insufficient to compensate for the preceding sodium retention. Alternate day pulsing does not, therefore, reduce the risk of sodium retention from large doses of methylprednisolone.

Electrolytes↗
PubMed1985

[Comparison of pulsed and continuous Doppler techniques for the evaluation of left ventricular stenoses].

The authors compared the data obtained with pulsed (pulsed Doppler-Scanner 3 MHz) and continuous wava Doppler (2.5 MHz), with that obtained by catheterisation in the evaluation of severity of valvular stenoses. The study material comprised 10 healthy subjects and 45 patients with mitral (21) and aortic (24 cases) stenosis, all of whom underwent catheterisation. Stenosis was graded in 3 degrees of increasing severity based on the catheter data. In addition, we studied the correlations between the transvalvular mitral and aortic pressure gradients, calculated by continuous Doppler and catheterisation, and the time of half decrease of flow measured by continuous Doppler and the mitral surface area calculated by catheterisation. No abnormality Was noted in the healthy patients. The jet of the aortic stenosis could not be recorded by continuous Doppler in 8 cases and aortic flow could not be recorded in 1 case with pulsed Doppler. The linear correlation with continuous Doppler was 0.96 (aortic transvalvular gradient for the 16 jets obtained), 0.81 (mitral transvalvular gradient), and 0.80 (time of half decrease of flow and mitral surface area calculated with catheterisation). The comparative study of the degree of severity gives the following percentages of success: mitral stenosis, 85% (pulsed Doppler) vs 71% (continuous Doppler) for mitral stenoses; aortic stenoses 83% (pulsed Doppler) vs 58% (continuous Doppler). In the 16 cases where the aortic jet was recorded properly this percentage was 87% (continuous Doppler) vs 81% (pulsed Doppler). In conclusion, the advantage of continuous Doppler over pulsed Doppler is that it provides quantitative parameters in correlation with catheter data. It is mainly used for evaluating recording the jet should significantly suggest that in elderly patients a systematic right parasternal approach in the jet should significantly reduce the failure rate observed in this study. It is of more limited value in mitral stenoses where pulsed Doppler gives more detailed information about the flow through the mitral valve. This, and the fact that pulsed Doppler can also be used for assession of aortic stenoses, illustrate the complementary nature of the two technique which should always be used together.

Adult↗
PubMed1984

Perturbation of the direction of neurite growth by pulsed and focal electric fields.

We have studied the orientation of neurite growth in the culture of embryonic Xenopus neurons in response to three types of extracellular electric fields: spatially uniform pulsed fields, focally applied steady (DC) fields, and focally applied pulsed fields. Under uniform pulsed fields, neurites showed a preferential orientation toward the cathode pole of the field in a manner similar to that previously found for DC fields. The extent of neurite orientation depended upon the duration, amplitude, and frequency of the pulse but appeared to be similar to that produced by a uniform DC field of an equivalent time-averaged field intensity. For square pulses of 5 msec duration, the minimal amplitude and frequency required to produce a detectable orientation of neurite growth over a period of 24 hr were 2.5 V/cm and 10 Hz, which correspond to a time-averaged field intensity of 125 mV/cm. Steady or pulsed focal fields were applied by passing a current through a micropipette placed near the growth cone of the neurite. Fields of negative polarity (current sink) were found to attract the growth cone, whereas fields of positive polarity (current source) were found to deflect the growth cone away from the pipette. The threshold DC current density needed at the growth cone to perturb its direction of growth within 15 min was 0.2 to 2 pA/micron2 (or 3 to 30 mV/cm); and for focal pulsed currents (pulse duration 5 msec), a typical combination of minimal pulse amplitude and frequency was 4 pA/micron2 and 10 Hz. This threshold focal current is similar to that which occurs at the synaptic cleft during active synaptic activity.

Animals↗