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Biomedical subjects

M Boehler

Publications and source records attributed to M Boehler.

15 recordsLinked to original sources
PubMed2006

Potential of activated sludge disintegration.

The disposal of sewage sludge and the agricultural use of stabilised sludge are decreasing due to more stringent regulations in Europe. An increasing fraction of sewage sludge must therefore be dewatered, dried, incinerated and the ashes disposed of in landfills. These processes are cost-intensive and also lead to the loss of valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Disintegration of biological sludge by mechanical, thermal and physical methods could significantly reduce excess sludge production, improve the settling properties of the sludge and reduce bulking and scumming. The solubilised COD could also improve denitrification if the treated sludge is recycled to the anoxic zone. However, disintegration partly inhibits and kills nitrifiers and could therefore shorten their effective solid retention time, thus reducing the safety of the nitrification. This paper discusses the potential of disintegration on sludge reduction, the operating stability of nitrification, the improvement of denitrification and also presents an energy and cost evaluation.

Cost-Benefit Analysis↗
PubMed2005

A new approach to improve sludge dewatering using a semi-continuous hydraulic press system.

In future, it will be necessary to incinerate an increasing proportion of the sludge produced by public wastewater treatment. In this context, equipment for more effective dewatering of sewage sludge is required. A hydraulic press system (Bucher HP) which has been used to date in the food industry could represent an alternative to the sludge dewatering systems currently used. The basic suitability of this press system was demonstrated in comprehensive industrial-scale trials at the Glarnerland STP (Switzerland). Dry solids contents of up to 43% were measured in the pressed sludge. Currently, the optimization of individual process parameters is being investigated in a pilot plant at the Schwelm STP operated by Wupperverband (Germany).

Bioreactors↗
PubMed2003

Clinical and simulator wear study of alumina ceramic THR to 17 years and beyond.

Three THAs with cementless monolithic alumina ceramic sockets and cementless Co-alloy stems were retrieved because of aseptic loosening after 17 and 24 years. At revision heads and cups were marked for orientation. Maps were drawn of wear patterns with the use of light microscopy and surveyed by SEM. In a simulator experiment 28-mm-diameter alumina heads and liners were used. The cups were mounted inverted in a hip simulator and run with calf serum as the lubricant. The hip loads were 2 kN maximum and a 1-Hz frequency for 20 million cycles. Wear severity was classified into five grades. In retrieved implants, SEM analysis showed that the main wear zones (MWZ) had Grade 4 wear. The peripheral wear zones (PWZ) showed grain pull-out regions (Grade 5 wear). These corresponded to neck-socket impingement and head-acetabular cup separation. Gray was due to transferred CoCr particles from the stem. In the simulator study, the MWZ had only localized areas of grain pull out surrounded by polished surface regions (Grade 4 wear) at 20 million cycles; stripe wear was not seen. The alumina ceramic bearings proved excellent up to 22 years in simulator studies and clinical studies. However, microseparation kinematics would be necessary in the simulator to duplicate the more peripheral wear zones.

Adult↗
PubMed2003

Progress in sensor technology--progress in process control? Part 1: sensor property investigation and classification.

To ensure correctly operating control systems, the measurement and control equipment in WWTPs must be mutually consistent. The dynamic simulation of activated sludge systems could offer a suitable tool for designing and optimising control strategies. Ideal or simplified sensor models represent a limiting factor for comparability with field applications. More realistic sensor models are therefore required. Two groups of sensor models are proposed on the basis of field and laboratory tests: one for specific sensors and another for a classification of sensor types to be used with the COST simulation benchmark environment. This should lead to a more realistic test environment and allow control engineers to define the requirements of the measuring equipment as a function of the selected strategy.

Environmental Monitoring↗
PubMed2001

Reversing sevoflurane-associated Q-Tc prolongation by changing to propofol.

Congenital or acquired forms of the long Q-T syndrome may result in ventricular tachycardia known as torsade de pointes. Many drugs including volatile anaesthetics modify the Q-T interval. Sevoflurane is known to prolong of the rate-corrected Q-T interval (Q-Tc). The objective of this study was to determine whether the sevoflurane-associated Q-Tc prolongation is rapidly reversible when propofol is substituted for sevoflurane. Thirty-two female patients were allocated to two groups. All patients received sevoflurane induction and anaesthesia for 15 min. In one group, sevoflurane was then discontinued and anaesthesia maintained on propofol for another 15 min. The second group received sevoflurane anaesthesia for 30 min. Measurements were taken before, and 15, 20, 25 and 30 min after induction. Q-Tc prolongation was significantly reduced 5, 10 and 15 min after propofol had been substituted for sevoflurane. We conclude that the sevoflurane-associated Q-Tc prolongation is fully reversible within 15 min when propofol is substituted for sevoflurane.

Adult↗
PubMed2001

Online monitoring of air quality at the postanesthetic care unit by proton-transfer-reaction mass spectrometry.

The subthreshold exposure to trace anesthetic gases is not associated with considerable risk of adverse health effects. Online control of ambient air exchange at the postoperative workplace may help in supervising air quality and lead to cost reduction. A proton-transfer-reaction mass spectrometer system was used for online monitoring of volatile organic compounds, especially anesthetic gases. The mean exposure to sevoflurane and isoflurane at the urological postanesthesia care unit (PACU) was 15.9 and 9.5 parts per billion, respectively. Sevoflurane and isoflurane concentrations at the urological PACU showed a patient turnover-dependent burden during our investigation period. Because modern PACUs have a high ventilation capacity, the 24-h occupational burden by anesthetic gases at the PACU is relatively low. Monitoring and controlling of ambient air by automatic built-in alarm systems would be useful for quality control of the postoperative workplace. Moreover, energy costs of ventilation systems could be reduced by coupling ventilation capacity to the effective exposure.

Air Pollutants, Occupational↗
PubMed2001

Debris from failed ceramic-on-ceramic and ceramic-on-polyethylene hip prostheses.

To compare the properties of wear debris between ceramic-on-ceramic and ceramic-on-polyethylene total hip prostheses, particles were isolated and characterized from tissue biopsies obtained at revision arthroplasty or autopsy from two similar uncemented modular hip systems. Group A hips (11 patients; mean, 31 months in vivo) had titanium shells with alumina inserts, alumina femoral heads, and titanium alloy stems. Group B hips (seven patients; mean, 42 months) were the same as Group A but with polyethylene acetabular inserts. Particles were characterized using an electrical resistance particle analyzer, scanning electron microscope, and energy dispersive xray spectroscope. Most of the particles in Group A were ceramic, whereas most of the particles in Group B were polyethylene. Metal particles from the femoral stem and the acetabular shell also were present. If one Group A hip with impingement is excluded, the rate of particle production is significantly lower in the ceramic-on-ceramic group than in the ceramic-on-polyethylene group. With the number of samples available, no significant difference in average size could be detected among the different types of particles or among the groups.

Ceramics↗
PubMed2000

Korean hand acupressure reduces postoperative vomiting in children after strabismus surgery.

A double-blind, randomized, placebo-controlled study was conducted to investigate the effectiveness of Korean hand acupuncture in preventing postoperative vomiting in children scheduled for strabismus surgery. In one group, acupressure was performed 30 min before induction of anaesthesia by applying an acupressure disc onto the Korean hand acupuncture point K-K9; the disc remained in situ for at least 24 h. The second group functioned as placebo group. The treatment groups did not differ with regard to patient characteristics, surgical procedure and anaesthetic administered. In the acupressure group, the incidence of vomiting was significantly lower (20%) than in the placebo group (68%). We conclude that Korean hand acupressure of the acupuncture point K-K9 is an effective method for reducing postoperative vomiting in children after strabismus repair.

Acupressure↗
PubMed2000

Cervical spine motion during airway management: a cinefluoroscopic study of the posteriorly destabilized third cervical vertebrae in human cadavers.

UNLABELLED: We conducted a randomized, controlled, crossover study to determine cervical spine motion for six airway management techniques in human cadavers with a posteriorly destabilized third cervical (C-3) vertebra. A destabilized C-3 segment was created in 10 cadavers (6-24 h postmortem). Cervical motion was recorded by continuous lateral fluoroscopy. The following airway management techniques were performed in random order on each cadaver with manual in-line stabilization applied: face mask ventilation (FM), laryngoscope-guided orotracheal intubation (OETT), fiberscope-guided nasal intubation (FOS-NETT), esophageal tracheal Combitube((R)) (Kendall-Sheridan, Neustadt, Germany) insertion (ETC), intubating laryngeal mask insertion with fiberscope-guided tracheal intubation (ILM-OETT), and laryngeal mask airway insertion (LMA). Afterward, maximum head-neck flexion (FLEX-MAX) and maximum head-neck extension (EXT-MAX) without manual in-line stabilization was performed to determine maximum motion. The maximum posterior displacement of C-3 and the maximum segmental sagittal motion of C2-3 were determined. There was a significant increase in posterior displacement for the FM (1.9 +/- 1.2 mm, P: < 0.01), OETT (2.6 +/- 1.6 mm, P: < 0.0001), ETC (3.2 +/- 1.6 mm, P: < 0.0001), ILM-OETT (1.7 +/- 1.3 mm, P: < 0. 01), LMA (1.7 +/- 1.3 mm, P: < 0.01), FLEX-MAX (3.7 +/- 1.9 mm, P: < 0.0001), EXT-MAX (1.8 +/- 1.7, P: < 0.01), however, not for FOS-NETT (0.1 +/- 0.7 mm). Posterior displacement was less for the ILM-OETT and LMA than for the ETC (both P: < 0.04). There were no significant increases in segmental sagittal motion with any airway manipulation other than with FLEX-MAX (-4.5 +/- 4.0 degrees, P: < 0.01). Posterior displacement was similar to FLEX-MAX for the OETT and ETC; however, it was less for the FM, FOS-NETT, ILM-OETT, and LMA (all P: < 0.01). Posterior displacement was similar to EXT-MAX for all airway manipulations other than for FOS-NETT (P: < 0.001). For cervical motion and the techniques tested, the safest method of airway management in a patient with a posteriorly destabilized C-3 segment is FOS-NETT. LMA devices may be preferable to the ETC. IMPLICATIONS: In the cadaver model of a destabilized third cervical vertebrae, significant displacement of the injured segment occurs during airway management with the face mask, laryngoscope-guided oral intubation, the esophageal tracheal Combitube (Kendall-Sheridan, Neustadt, Germany), the intubating and standard laryngeal mask airway; but not with fiberscope-guided nasal intubation. For cervical motion and the techniques tested, the safest airway technique with this injury is fiberscope-guided nasotracheal intubation. Laryngeal mask devices are preferable to the esophageal tracheal Combitube.

Aged↗
PubMed2000

Alumina ceramic bearings for hip endoprostheses: the Austrian experiences.

The current authors review clinical and retrieval experiences with hemispheric monolithic alumina ceramic sockets (Group 1), implanted between 1976 and 1979, and similar modular titanium sockets with alumina ceramic inlays (Group 2), implanted between 1990 and 1995. Both cementless sockets articulated with alumina ceramic femoral ball heads for total hip joint replacements. Clinical followup of patients with hemispheric monolithic alumina ceramic sockets (Group 1, 138 sockets) resulted in a total failure rate of 19.6% after 5 to 20 years. Radiologic analysis of eight stable sockets showed migration of 0.2 mm to 2.89 mm, but in four sockets at risk for late aseptic failure after an average followup of 12.5 years as much as 13.4 mm of migration was seen. Histologic evaluation revealed pseudosynovial membranes as thick as 1 mm with fine birefringent wear particles within mononuclear macrophages around two stable retrieved sockets. The membranes around four loose sockets were 6 to 10 mm thick and also heavily loaded with larger alumina wear particles. After 7 years followup clinical analysis of patients with modular titanium sockets with alumina ceramic inlays (Group 2, 30 sockets) resulted in four revisions, compared with one revision of 50 identical sockets (control group) with polyethylene instead of alumina ceramic inlays. Wear particle analyses in scanning electron microscopy showed significantly more particles (x 10(9) +/- standard deviation/g dry tissue) from the control group (4.26+/-6.38), compared with alumina ceramic bearings of Group 1 (0.70+/-0.79), and of Group 2 (1.62+/-2.13). The alumina particle sizes ranged between 0.13 and 78.38 microm. The mean annual linear wear of 38.8 microm was calculated for the bearings in Group 1, and of 26.94 microm for bearings in Group 2. These results support the good tribologic and biologic performance of alumina ceramic bearings for total hip arthroplasty.

Aluminum Oxide↗
PubMed1996

Antibiotic-associated colitis in orthopaedic patients.

Antibiotic-associated colitis was diagnosed in 23 orthopaedic patients: 17 had abdominal symptoms, 3 had a fever and the remaining 3 had no symptoms but increasing C-reactive protein values or white blood count. The antibiotic was clindamycin in 19, cephalosporins in 3 and a combination of vancomycin and fusidic acid intravenously in one. The antibiotics were stopped in 12, changed in 5 and continued in the remaining 5. Oral treatment for colitis was given in 21 patients, and in one patient the only treatment was stopping the antibiotics. One patient died after a myocardial infarct; the remaining 22 were discharged after successful treatment of their primary condition and the colitis.

Adult↗
PubMed1994

Long-term results of uncemented alumina acetabular implants.

We report the clinical and tribological performance of 67 ceramic acetabular prostheses implanted between 1976 and 1979 without bone cement. They articulated with ceramic femoral heads mounted on mental femoral stems. After a mean elapsed period of 144 months, 59 sockets were radiographically stable but two showed early signs and six showed late signs of loosening. Four of the loose sockets have been revised. Histological analysis of the retrieved tissue showed a fibrous membrane around all the implants, with fibrocartilage in some. There was no bone ingrowth, and the fibrous membrane was up to 6 mm thick and infiltrated with lymphocytes, plasma cells, and macrophages. Intra- and extracellular birefringent wear particles were seen. Tribological analysis showed total wear rates in two retrieved alumina-on-alumina joints of 2.6 microns per year in a stable implant and 68 microns in a loose implant. Survival analysis showed a revision rate of 12.4% at 136 months.

Adult↗