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  • 1995-1999  (6)
  • 1940-1944
  • Conductivity  (2)
  • Pericardial pressure  (2)
  • calcium phosphate  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Haemodynamic and respiratory conditions during alternating and synchronous ventilation of both lungs (1996)
    Springer
    Intensive care medicine 22 (1996), S. 813-817 
    Details
    ISSN: 1432-1238
    Keywords: Key words Alternating ventilation ; Cardiac output ; Central venous pressure ; Intrathoracic pressure ; Lung volume ; Pericardial pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract   Objective: We tested the hypothesis that mean thoracic expansion (and mean lung volume) is lower during alternating ventilation (AV), i.e. ventilation of both lungs with a phase shift of half a ventilatory cycle, compared to synchronous ventilation (SV) of both lungs. As a consequence, intrathoracic pressure will be lower, causing lower, central venous pressure and higher cardiac output. Design: In eight anaesthetized and paralysed piglets, differential ventilation was established by fixation of an endobronchial tube in the left main bronchus. SV and AV were sequentially applied for four and three periods, respectively, of 10 minutes each. Minute ventilation was the same during AV and SV and adapted to normocapnia. Two series of observations were performed: series 1 with intact thorax and monitoring of oesophageal pressure; series 2 after perforation of the sternum, airtight closure of the thorax and monitoring of pericardial pressure. Results: In both series, mean lung volume was 16±4% lower and central venous, oesophageal (series 1) and pericardial pressures (series 2) were 0.5–0.7 mmHg lower during AV compared to SV (all p〈0.001). In series 1, aortic pressure was 5 mmHg and cardiac output 8% higher (both p〈0.001). In series 2, cardiac output was 5% higher during AV (p〈0.001), but aortic pressure did not change (p=0.07). Conclusion: Our data verified the hypothesis. The lower oesophageal (series 1), pericardial (series 2) and central venous pressures during AV compared to SV could be explained by the smaller thoracic expansion due to the lower mean lung volume, which was attributed to compression of the opposite lung by the expansion of the inflated lung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01709526
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Haemodynamic and respiratory conditions during alternating and synchronous ventilation of both lungs (1996)
    Springer
    Intensive care medicine 22 (1996), S. 813-817 
    Details
    ISSN: 1432-1238
    Keywords: Alternating ventilation ; Cardiac output ; Central venous pressure ; Intrathoracic pressure ; Lung volume ; Pericardial pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective We tested the hypothesis that mean thoracic expansion (and mean lung volume) is lower during alternating ventilation (AV), i.e. ventilation of both lungs with a phase shift of half a ventilatory cycle, compared to synchronous ventilation (SV) of both lungs. As a consequence, intrathoracic pressure will be lower, causing lower, central venous pressure and higher cardiac output. Design In eight anaesthetized and paralysed piglets, differential ventilation was established by fixation of an endobronchial tube in the left main bronchus. SV and AV were sequentially applied for four and three periods, respectively, of 10 minutes each. Minute ventilation was the same during AV and SV and adapted to normocapnia. Two series of observations were performed: series 1 with intact thorax and monitoring of oesophageal pressure; series 2 after perforation of the sternum, airtight closure of the thorax and monitoring of pericardial pressure. Results In both series, mean lung volume was 16±4% lower and central venous, oesophageal (series 1) and pericardial pressures (series 2) were 0.5±0.7 mmHg lower during AV compared to SV (allp〈0.001). In series 1, aortic pressure was 5 mmHg and cardiac output 8% higher (bothp〈0.001). In series 2, cardiac output was 5% higher during AV (p〈0.001), but aortic pressure did not change (p=0.07). Conclusion Our data verified the hypothesis. The lower oesophageal (series 1), pericardial (series 2) and central venous pressures during AV compared to SV could be explained by the smaller thoracic expansion due to the lower mean lung volume, which was attributed to compression of the opposite lung by the expansion of the inflated lung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01709526
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Determination of the mean cross-sectional area of the thoracic aorta using a double indicator dilution technique (1996)
    Springer
    Pflügers Archiv 432 (1996), S. 1069-1073 
    Details
    ISSN: 1432-2013
    Keywords: Key words Arteries ; Conductivity ; Conductance method ; Double indicator dilution method ; Shear rate ; Intravascular ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A double indicator dilution technique for determining the mean cross-sectional area (CSA) of a blood vessel in vivo is presented. Analogous to the thermodilution method, dilution of hypertonic saline was measured by an electrical conductance technique. Because the change in conductance rather than absolute conductance was used to calculate CSA, pulsatile changes in shear rate of blood and conductance of surrounding tissues had no effect on the data. To calculate CSA from an ion mass balance, cardiac output was needed and estimated from the thermodilution curve using the same “cold” (hypertonic) saline injection. The mean CSA, obtained from this double indicator dilution method (CSAGD), was compared with the CSA obtained from the intravascular ultrasound method (IVUS) in 44 paired observations in six piglets. The regression line is close to the line of identity (CSAGD = −1.83 + 1.06⋅CSAIVUS, r = 0.96). The difference between both CSAs was independent of the diameter of the vessel, on average −0.99 mm2± 2.64 mm2 (mean CSAGD = 46.84 ± 8.21 mm2, mean CSAIVUS = 47.82 ± 9.08 mm2) and not significant. The results show that the double indicator dilution method is a reliable technique for estimating the CSA of blood vessels in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050236
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Conductance Method for the Measurement of Cross-Sectional Areas of the Aorta (1999)
    Springer
    Annals of biomedical engineering 27 (1999), S. 141-150 
    Details
    ISSN: 1573-9686
    Keywords: Conductivity ; Erythrocytes ; Ultrasound ; Shear stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A modified conductance method to determine the cross-sectional areas (CSAs) of arteries in piglets was evaluated in vivo. The method utilized a conductance catheter having four electrodes. Between the outer electrodes an alternating current was applied and between the inner electrodes the induced voltage difference was measured and converted into a conductance. CSA was determined from measured conductance minus parallel conductance, which is the conductance of the tissues surrounding the vessel times the length between the measuring electrodes of the conductance catheter divided by the conductivity of blood. The parallel conductance was determined by injecting hypertonic saline to change blood conductivity. The conductivity of blood was calculated from temperature and hematocrit and corrected for maximal deformation and changes in orientation of the erythrocytes under shear stress conditions. The equations to calculate the conductivity of blood were obtained from in vitro experiments. In vivo average aortic CSAs, determined with the conductance method CSA (G) in five piglets, were compared to those determined with the intravascular ultrasound method CSA(IVUS). The regression equation between both values was CSA (G) =−0.09+1.00·CSA(IVUS) r=0.97, n=53. The mean difference between the values was −0.29% · 5.57% (2 standard deviations). We conclude that the modified conductance method is a reliable technique to estimate the average cross-sectional areas of the aorta in piglets. © 1999 Biomedical Engineering Society. PAC99: 8780-y, 8437+q, 8719Nn
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.219
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of rapid heating with infrared radiation on RF magnetron-sputtered calcium phosphate coatings (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 37 (1997), S. 60-67 
    Details
    ISSN: 0021-9304
    Keywords: heat treatment ; calcium phosphate ; coating ; sputter ; implant ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study evaluated the effect of rapid heating with infrared radiation on the physico-chemical and morphological properties of radio frequent (RF) magnetron-sputtered calcium phosphate (Ca-P) coatings. About 2.5 μm thick Ca-P coatings were deposited on titanium disks and cylinders. These specimens were left untreated or were heat treated by infrared radiation at 300, 400, 500, 600, and 700°C for 4, 7, 11, 17, and 24 s. Subsequently, the specimens were immersed in simulated body fluid (SBF) for 1 day, 1 week, and 5 weeks. X-ray diffraction measurements showed that heating at 500°C or higher resulted in an increase of coating crystallinity. In addition, FT-IR measurements revealed the appearance of OH peaks in the spectra of samples treated at 500-700°C. Electron probe microanalysis showed that after 5 weeks of immersion about 40-50% of the coatings heat treated at 500 and 600°C was maintained. The coatings heat treated at 700°C showed no dissolution at all. On the other hand, as-coated and 300°C treated films were dissolved within 1 day. Scanning electron microscopy of the samples showed that directly after heat treatment no apparent cracks were present in the coatings. On the basis of these findings, we conclude that rapid heating with infrared radiation around 600°C is the best heat treatment for RF magnetron-sputtered coatings. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 37, 60-67, 1997.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    A complete characterization of Ca5(PO4)3OH sputter-deposited films by ion beam analysis: RBS and ERD (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 266-271 
    Details
    ISSN: 0021-9304
    Keywords: calcium phosphate ; ion beam analysis ; coating ; Rutherford backscattering ; elastic recoil detection ; biomaterial ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: RF magnetron sputter deposition was used to deposit thin calcium phosphate (hydroxyapatite) layers on titanium alloy substrate material. We determined the precise amount of calcium, phosphorus, oxygen, and hydrogen in these films by combining two ion-beam analysis techniques: Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD). Variables were power level, partial oxygen pressure, or additional water vapor. Also examined was the influence of additional bias power to the substrates during deposition and the effect of annealing on the final composition of the deposited layers. Measurements showed that the Ca/P ratio decreased with increasing oxygen pressure or decreasing sputtering power. In addition, the Ca/P ratio increased when a bias was applied to the substrates. The O/P ratio of the films decreased with additional oxygen pressure but increased when additional water vapor was applied during deposition. All as-deposited films showed a higher hydrogen content than stoichiometric HA. The hydrogen content in the films deposited with water vapor was more than 7 times higher than in the films deposited under pure argon conditions. After annealing, the hydrogen content decreased to about 3.5 at % whereas in stoichiometric HA the hydrogen content amounts to 4.5 at %. After annealing, the oxygen concentration in the film also decreased. We assume that hydrogen disappears out of the film as H2O during annealing. For the targets used in these experiments, sputter deposition at 400 W, with additional water vapor and annealing at 500°C, produced films with a stoichiometry closest to that of hydroxyapatite. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 266-271, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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