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John A. Jansen - One of the best experts on this subject based on the ideXlab platform.
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Closing Capacity of segmental radius defects in rabbits.
Journal of biomedical materials research. Part A, 2008Co-Authors: Esther W.h. Bodde, Paul H.m. Spauwen, Antonios G. Mikos, John A. JansenAbstract:In the research of synthetic bone graft substitutes, the relevance for bone regeneration can be confirmed in a critical-sized model. In this study the rabbit radial defect was investigated as an ingenious model of critical size, due to its defect immobilizing intact ulna. In addition, the influence of poly(DL-lactic-co-glycolic acid) (PLGA) on bone regeneration was determined. Sixteen, 4-month-old rabbits received bilateral segmental radial defects of 15 or 20 mm. The osteotomy ends were marked with small titanium pins. Half of the group received injected PLGA microparticle/carboxymethylcellulose implants. Implantation time was 12 weeks. Evaluation consisted of radiographs after surgery and sacrifice, microcomputed tomography and histology. The radiographs revealed that the created defects were significantly smaller after sacrifice. Further a number of radii showed fibrocartilaginous interposition. Both findings indicated instability of the created defect. All evaluation techniques revealed that 15 and 20 mm were not of critical size, as most defects were more or less regenerated. PLGA microparticles did not influence bone regeneration significantly. In conclusion, 15- and 20-mm radius defects in 4-month-old rabbits were not a suitable model for bone regeneration as these defects were neither critical size nor stable. PLGA-microparticle degradation did not influence bone regeneration.
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Closing Capacity of cranial bone defects using porous calcium phosphate cement implants in a rabbit animal model.
Journal of biomedical materials research. Part A, 2006Co-Authors: H.c. Kroese-deutman, Paul H.m. Spauwen, Joop G.c. Wolke, John A. JansenAbstract:Calcium phosphate (Ca-P) cement is a well established material for bone repair. The bone biological properties of Ca-P cement can even be further improved by creating porosity in the material. The current study aimed on the evaluation of the osteoconductive behavior of porous Ca-P cement. Therefore, circular defects (6, 9, and 15 mm in diameter) were created in the cranium of 3 months old rabbits and filled with porous Ca-P cement implants. The total porosity of implants was calculated to be 71, 74 and 74% respectively and the average pore diameter was 150 microm. In addition, empty control defects were prepared. After 12 weeks implantation time the animals were sacrificed and radiographic, histological, and histomorphometrical evaluation was performed. The Critical Size Defect (CSD) of this species at this location for an implantation time of 12 weeks was confirmed to be 15 mm. Bone was observed to be present over and through almost all porous Ca-P cement implants. Only, in one out of eight animals with a 15 mm implant complete bone bridging of the defect did not occur. The size of the defect was found not to affect the total percentage of bone formation in the cement; (17 +/- 7)%, (18 +/- 6)% and (17 +/- 3)% for respectively 6, 9, and 15 mm diameter implants. We concluded that porous Ca-P cement is an excellent osteoconductive material in non weight bearing situations and complete bridging of a critical sized skull defect occurs in this rabbit model after 12 weeks of implantation.
Q. T. Pham - One of the best experts on this subject based on the ideXlab platform.
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Computerized single-breath nitrogen washout: Predicted values in a rural French community
Lung, 1996Co-Authors: D. B. Teculescu, M.-c. Daniel, E. Costantino, O. Buhler, A. B. Bohadana, M. Marchand, Q. T. PhamAbstract:Comparative manual and computer measurements of the alveolar N_2 slope and Closing volumes have indicated systematic differences. When a computerized system is used in field surveys, predicted values are to be obtained under the same conditions. Therefore, we measured the alveolar nitrogen slope (phase ITI, PIII), Closing volume (CV), and Closing Capacity (CC) from single-breath N_2 washout maneuvers in 158 healthy subjects (68 females), ages 21 to 64 years, from a rural community living in a nonpolluted area of northeast France. PIII, the CV to vital Capacity ratio (CV:VC, %), and the CC to the total lung Capacity ratio (CC:TLC, %) were regressed against age, height, weight, and the body mass index (BMI, kg/m^2) and prediction equations with 95% confidence intervals were computed. PIII increased with age in both sexes and tended to decrease with height in males ( r = −0.19, p = .08). The CV:VC and CC: TLC ratios depended on age and, in males, increased with the BMI. Despite accepting a 15% difference between the test VC and the spirometric VC, only 46.3% of asymptomatic nonsmokers produced a valid single-breath nitrogen washout (SBN_2) test. This high failure rate limits the usefulness of the test for epidemiologic purposes when older populations “naive” to pulmonary function testing are studied under field-survey conditions.
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Variability of the computerized single‐breath nitrogen washout test in healthy adults. Results from a field survey in a French rural area
Clinical physiology (Oxford England), 1993Co-Authors: Dan B. Teculescu, Q. T. Pham, E. Costantino, E. Rebstock, I. Caillier, O. BouchyAbstract:Summary. Within-subject (difference between paired tests, or coefficient of variation [c. var.] of three consecutive measurements) and between-subjects (standard deviation of the mean group) variability were assessed for the variables derived from the single-breath nitrogen (SBN2) test in a group of healthy, asymptomatic subjects (n= 289) aged 20–64 years, from a rural area in North-East France. Duplicate measurements in 99 subjects showed excellent agreement between the two attempts (correlation coefficients between 0.94 and 0.98) for static lung volumes and the alveolar N2 slope (PIII); Closing volumes (CV) were more variable (r= 0.77 for absolute value, 0.79 for % VC) while Closing capacities (CC) were in intermediate position (r= 0.86 for absolute value, and 0.88 for % TLC). The variability of three consecutive measures in 190 subjects showed the coefficients of variation to be low for static volumes and Closing Capacity (2.4–7.4%) and higher for PIII (15.1%) and CV or CV7VC (18.2 and 17.8%). The analysis of variance did not detect significant differences between the three sets of measurements, with the exception of a progressive increase of vital Capacity (VC), and decrease in residual volume (RV) from test 1 to test 3, the total lung Capacity being the same. Variability was uninfluenced by age or sex, except a higher c. var. for female VC as compared to males (2.8 vs. 2.2%, P= 0.02) and a higher variability of TLC (2.9 vs. 2.3%, P= 0.03) and VC (2.8 vs. 1.9%, P= 0.003) in people older than 40 years as opposed to those younger than 40 years.
Joseph Milic-emili - One of the best experts on this subject based on the ideXlab platform.
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Closing Capacity and Gas Exchange in Chronic Heart Failure
Chest, 2006Co-Authors: Roberto Torchio, Carlo Gulotta, Pietro Greco-lucchina, Alberto Perboni, Laura Montagna, Marco Guglielmo, Joseph Milic-emiliAbstract:Background Although it is commonly assumed that pulmonary congestion and edema in patients with chronic heart failure (CHF) promotes peripheral airway closure, Closing Capacity (CC) has not been measured in CHF patients. Purpose To measure CC and the presence or absence of airway closure and expiratory flow limitation (FL) during resting breathing in CHF patients. Methods In 20 CHF patients and 20 control subjects, we assessed CC, FL, spirometry, blood gas levels, control of breathing, breathing pattern, and dyspnea. Results The patients exhibited a mild restrictive pattern, but the CC was not significantly different from that in control subjects. Nevertheless, airway closure during tidal breathing ( ie , CC greater than functional residual Capacity [FRC]) was present in most patients but was absent in all control subjects. As a result of the maldistribution of ventilation and the concurrent impairment of gas exchange, the mean (± SD) alveolar-arterial oxygen pressure difference increased significantly in CHF patients (4.3 ± 1.2 vs 2.7 ± 0.5 kPa, respectively; p r = 0.49; p 0.1 ) as a percentage of maximal inspiratory pressure (P i max) together with ventilation were increased in CHF patients (p f R) with a concurrent decrease in Pa co 2 . Chronic dyspnea (scored with the Medical Research Council [MRC] scale) correlated ( r 2 = 0.61; p f R and P 0.1 /P i max. Conclusions In CHF patients at rest, CC is not increased, but, as a result of decreased FRC, airway closure during tidal breathing is present, promoting the maldistribution of ventilation, ventilation-perfusion mismatch, and impaired gas exchange. The ventilation is increased as result of increased f R, and P i max is decreased with a concurrent increase in P 0.1 , implying that there is a proportionately greater inspiratory effort per breath (P 0.1 /P i max ) . These, together with the increased f R, are the only significant contributors to increases in the MRC dyspnea score.
Paul H.m. Spauwen - One of the best experts on this subject based on the ideXlab platform.
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Closing Capacity of segmental radius defects in rabbits.
Journal of biomedical materials research. Part A, 2008Co-Authors: Esther W.h. Bodde, Paul H.m. Spauwen, Antonios G. Mikos, John A. JansenAbstract:In the research of synthetic bone graft substitutes, the relevance for bone regeneration can be confirmed in a critical-sized model. In this study the rabbit radial defect was investigated as an ingenious model of critical size, due to its defect immobilizing intact ulna. In addition, the influence of poly(DL-lactic-co-glycolic acid) (PLGA) on bone regeneration was determined. Sixteen, 4-month-old rabbits received bilateral segmental radial defects of 15 or 20 mm. The osteotomy ends were marked with small titanium pins. Half of the group received injected PLGA microparticle/carboxymethylcellulose implants. Implantation time was 12 weeks. Evaluation consisted of radiographs after surgery and sacrifice, microcomputed tomography and histology. The radiographs revealed that the created defects were significantly smaller after sacrifice. Further a number of radii showed fibrocartilaginous interposition. Both findings indicated instability of the created defect. All evaluation techniques revealed that 15 and 20 mm were not of critical size, as most defects were more or less regenerated. PLGA microparticles did not influence bone regeneration significantly. In conclusion, 15- and 20-mm radius defects in 4-month-old rabbits were not a suitable model for bone regeneration as these defects were neither critical size nor stable. PLGA-microparticle degradation did not influence bone regeneration.
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Closing Capacity of cranial bone defects using porous calcium phosphate cement implants in a rabbit animal model.
Journal of biomedical materials research. Part A, 2006Co-Authors: H.c. Kroese-deutman, Paul H.m. Spauwen, Joop G.c. Wolke, John A. JansenAbstract:Calcium phosphate (Ca-P) cement is a well established material for bone repair. The bone biological properties of Ca-P cement can even be further improved by creating porosity in the material. The current study aimed on the evaluation of the osteoconductive behavior of porous Ca-P cement. Therefore, circular defects (6, 9, and 15 mm in diameter) were created in the cranium of 3 months old rabbits and filled with porous Ca-P cement implants. The total porosity of implants was calculated to be 71, 74 and 74% respectively and the average pore diameter was 150 microm. In addition, empty control defects were prepared. After 12 weeks implantation time the animals were sacrificed and radiographic, histological, and histomorphometrical evaluation was performed. The Critical Size Defect (CSD) of this species at this location for an implantation time of 12 weeks was confirmed to be 15 mm. Bone was observed to be present over and through almost all porous Ca-P cement implants. Only, in one out of eight animals with a 15 mm implant complete bone bridging of the defect did not occur. The size of the defect was found not to affect the total percentage of bone formation in the cement; (17 +/- 7)%, (18 +/- 6)% and (17 +/- 3)% for respectively 6, 9, and 15 mm diameter implants. We concluded that porous Ca-P cement is an excellent osteoconductive material in non weight bearing situations and complete bridging of a critical sized skull defect occurs in this rabbit model after 12 weeks of implantation.
D. B. Teculescu - One of the best experts on this subject based on the ideXlab platform.
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Computerized single-breath nitrogen washout: Predicted values in a rural French community
Lung, 1996Co-Authors: D. B. Teculescu, M.-c. Daniel, E. Costantino, O. Buhler, A. B. Bohadana, M. Marchand, Q. T. PhamAbstract:Comparative manual and computer measurements of the alveolar N_2 slope and Closing volumes have indicated systematic differences. When a computerized system is used in field surveys, predicted values are to be obtained under the same conditions. Therefore, we measured the alveolar nitrogen slope (phase ITI, PIII), Closing volume (CV), and Closing Capacity (CC) from single-breath N_2 washout maneuvers in 158 healthy subjects (68 females), ages 21 to 64 years, from a rural community living in a nonpolluted area of northeast France. PIII, the CV to vital Capacity ratio (CV:VC, %), and the CC to the total lung Capacity ratio (CC:TLC, %) were regressed against age, height, weight, and the body mass index (BMI, kg/m^2) and prediction equations with 95% confidence intervals were computed. PIII increased with age in both sexes and tended to decrease with height in males ( r = −0.19, p = .08). The CV:VC and CC: TLC ratios depended on age and, in males, increased with the BMI. Despite accepting a 15% difference between the test VC and the spirometric VC, only 46.3% of asymptomatic nonsmokers produced a valid single-breath nitrogen washout (SBN_2) test. This high failure rate limits the usefulness of the test for epidemiologic purposes when older populations “naive” to pulmonary function testing are studied under field-survey conditions.