Biomedical subjects

C Gutt

Publications and source records attributed to C Gutt.

At least 19 recordsLinked to original sources

PubMed2005

Surface roughness and adsorption isotherms of molecularly thin liquid films: an x-ray reflectivity study.

We present an x-ray reflectivity study of molecularly thin films of liquid isobutane adsorbed on liquid glycerol. The glycerol-isobutane interface serves as a model system to investigate the influence of the substrate adsorbate interactions on both adsorption isotherms and capillary wave fluctuations. The measured surface roughness is smaller than expected from the harmonic approximation of the interaction potential. Expressions for the surface roughness in slightly anharmonic potentials are given and compared to the experimental data. A good agreement between data and theory is achieved.

Journal Article↗

PubMed2005

Anharmonic motions of Kr in the clathrate hydrate.

The anomalous glass-like thermal conductivity of crystalline clathrates has been suggested to be the result of the scattering of thermal phonons of the framework by 'rattling' motions of the guests in the clathrate cages. Using the site-specific (83)Kr nuclear resonant inelastic scattering spectroscopy in combination with conventional incoherent inelastic neutron scattering and molecular-dynamics simulations, we provide unambiguous evidence and characterization of the effects on these guest-host interactions in a structure-II Kr clathrate hydrate. The resonant scattering of phonons led to unprecedented large anharmonic motions of the guest atoms. The anharmonic interaction underlies the anomalous thermal transport in this system. Clathrates are prototypical models for a class of crystalline framework materials with glass-like thermal conductivity. The explanation of the unusual molecular dynamics has a wide implication for the understanding of the thermal properties of disordered solids and structural glasses.

Computer Simulation↗

PubMed2004

Surface roughness of supercooled polymer melts.

We report on in situ x-ray reflectivity measurements of the surface roughness of supercooled glass forming polymers in a temperature range from 190 to 330 K. The experimentally determined rms roughness has been found to obey the capillary wave model of a single liquid/vapor interface over the entire temperature range. An expression for the surface roughness below the bulk glass transition (T(G) approximately equal to 200 K) is deduced from the viscoelastic theory of surface fluctuations; however, no indication of a frozen-in surface roughness has been observed in the experiment. Additionally, it is shown that precise values of the surface tension of highly viscous liquids in the supercooled state can be determined by x-ray reflectivity.

Journal Article↗

PubMed2004

The structure of methane hydrate under geological conditions a combined Rietveld and maximum entropy analysis.

We present a study of the structure of a fully deuterated methane hydrate under the geological conditions found in the world's oceans. In situ high-resolution neutron diffraction experiments have been performed at temperatures of 220, 275, and 280 K and a pressure of 100 bar, corresponding to the conditions at 1000 m water depth. The data were analyzed with a combination of Rietveld refinement and maximum entropy methods. From the Rietveld refinement, precise atomic parameters of the host lattice could be determined, indicating increasing distortions of the structure of the cages at elevated temperatures and pressures. Debye-Waller factors of the encaged CD(4) molecules have been found to exceed the values of the Debye-Waller factors of the D(2)O molecules considerably. In the large cage of structure type I the thermal center-of-mass displacements of the guests are 5-10 times larger than those of the water molecules. From the maximum entropy analysis maps of the scattering length density have been obtained, showing details of the vibrational amplitudes of the atoms in methane hydrate. The Debye-Waller factors of all molecules have been found to deviate considerably from a simple spherical geometry.

Journal Article↗

PubMed2004

Capillary waves at the transition from propagating to overdamped behavior.

We measure the dispersion relation of capillary waves on a liquid surface by heterodyne x-ray photon correlation spectroscopy near the transition from propagating to overdamped dynamic behavior. A strong deviation of the propagation frequency from the small-damping result omega(p) proportional, variant k(3/2) is observed long before the actual transition where ( partial differential omega(p)/ partial differential k)<0 and omega(p) tends to zero. This behavior is successfully described by expressions derived within linear response theory.

Journal Article↗

PubMed2004

Phase behaviour of n-hexane/perfluoro-n-hexane binary thin wetting films.

We present X-ray reflectivity investigations of the concentration distribution in binary liquid thin films on silicon substrates. The liquid-vapor coexistence of the binary mixture investigated, hexane and perfluorohexane, is far from criticality. Therefore, a sharp interface separates the liquid film from the vapor. The data reveal a separation of the film in layers parallel to the substrate. A phase diagram is constructed as a projection to the (composition difference, temperature) space, covering a temperature range corresponding to the one-phase and the two-phase regime of the bulk liquid. Although the composition data indicate a mixing gap similar to that of the bulk system, there are two major differences: i) only the near-surface phase changes its composition significantly, and ii) a composition gradient in the film exists also at higher temperatures where in the bulk system the one-phase regime exists.

Biophysics↗

PubMed2003

Observation of heterodyne mixing in surface x-ray photon correlation spectroscopy experiments.

We report measurements of propagating capillary waves on a liquid water surface at T=5 degrees C with x-ray photon correlation spectroscopy. The experiment has been performed under grazing incidence conditions with an incoming x-ray beam below the critical angle of total external reflection. In the q region investigated the measured intensity-intensity autocorrelation functions of the liquid water surface were found to be heterodyne signals, i.e., a combination of first- and second-order correlation functions g(1)(tau) and g(2)(tau).

Journal Article↗

PubMed2002

Transoesophageal echocardiography shows high risk of gas embolism during laparoscopic hepatic resection under carbon dioxide pneumoperitoneum.

BACKGROUND: The ultrasonically activated scalpel (UAS) enables safe and effective laparoscopic tissue dissection, making hepatic resection feasible. This study compared blood loss and risk of gas embolism using the UAS during open hepatic resection and laparoscopic hepatic resection. METHODS: Female pigs were divided into two groups for laparoscopic (n = 7) and open (n = 5) left hepatic lobectomy. The UAS was used for both tissue cutting and coagulation. Laparoscopic liver resection was performed under carbon dioxide pneumoperitoneum (intraperitoneal pressure 12 mmHg). During surgery animals were monitored haemodynamically by an arterial line and Swan-Ganz catheter. Two-dimensional transoesophageal echocardiography (2D-TEE) was used to detect gas emboli with special attention to the right atrium and ventricle. Gas emboli were graded according to size, and correlated with haemodynamic and blood gas data. RESULTS: During open and laparoscopic hepatic resection the UAS resulted in minimal blood loss and effective tissue dissection. No air embolism was seen during open surgery. With laparoscopic hepatic resection 2D-TEE revealed gas embolism in all animals. Gas embolism was accompanied by cardiac arrhythmia in four of seven animals. No direct correlation was observed between embolism episodes and blood gas variables. There were no deaths after episodes of embolization. A significant decrease in arterial partial pressure of oxygen was seen at the end of the laparoscopic procedure in all animals. CONCLUSION: The UAS causes minimal blood loss during both open and laparoscopic hepatic resection. Laparoscopic liver dissection under carbon dioxide pneumoperitoneum carries a high risk of gas embolism.

Animals↗

PubMed2002

Use of the robot system Da Vinci for laparoscopic repair of gastro-oesophageal reflux in children.

In adult patients, laparoscopic surgery, using a robot system (Da Vinci, Intuitive Surgical, Mountain View, California), has been recently introduced into surgical practice. To investigate the feasibility of the system in paediatric surgery, laparoscopic fundoplications as well as cholecystectomies have been performed. In July 2000 we used the robot system for the first time on an 11-year-old girl with gastro-oesophageal reflux, and since that time on 7 other children. Altogether 5 Thal and 3 Nissen procedures have been carried out. The average age was 12 years, with a range of 7 to 16 years. All operations were performed without complications and without conversion to open surgery. The medium operating time was 146 min with a range of 105 to 180 minutes. Compared to conventional laparoscopy, the 3-dimensional high-quality vision, the advanced instrument movements and the ergonomic position of the surgeon seems to enhance surgical precision. In our opinion, the use of the robot system is feasible and safe in paediatric surgery. The technique is limited due to the fact that instruments adapted to the size of small children are not yet available.

Adolescent↗

PubMed2001

Oncologic implications of laparoscopic and open surgery.

Although instrumental manipulation and mechanical tumor cell spillage seem to play the major role in port-site metastases from laparoscopic cancer surgery, minimally invasive procedures are used more and more in the resection of malignancies. However, port-site metastases also have been reported after resection of colon cancer in International Union Against Cancer (UICC) stage I [2, 14]. Therefore, changes in the peritoneal environment during laparoscopy also might influence intra- and extraperitoneal tumor growth during laparoscopy and pneumoperitoneum. Different results of experimental studies presented at the Third International Conference for Laparoscopic Surgery are analyzed and discussed.

Animals↗

PubMed2001

[Robot-assisted laparoscopic cholecystectomy and fundoplication--initial experiences with the Da Vinci system].

We report on our first five robot-assisted laparoscopic cholecystectomies and one fundoplication (Da Vinci system). No postoperative complications were observed. For the cholecystectomies (three elective and two acute cases) mean operation time was 1 h 35 min, and mean hospital stay was 5 days; for fundoplication the operation time was 2 h 15 min. The main advantages seem to be improved visualization by using a stereo camera und ease of precise dissection by micromechanical instruments directed by masterslaves from a distant console. The main disadvantage is the high cost. To fully evaluate the benefit for the patient, prospective clinical trials are warranted.

Cholecystectomy, Laparoscopic↗

PubMed1999

Tumor seeding following laparoscopy: international survey.

The aim of the study was to determine if tumor seeding during laparoscopic surgery for cancer is a rare event or a typical complication of this procedure. Laparoscopic staging and treatment of intraabdominal tumors is increasing in gastroenterology, gynecology, and general surgery. A total of 1052 questionnaires were mailed to surgical department chairmen, members of the German Society of Surgery, Swiss Association for Laparoscopic and Thoracoscopic Surgery, and Austrian Society of Minimal Invasive Surgery asking them to list their department's experience with tumor seeding after laparoscopy for nonapparent or known malignancy. There were 607 (57.7%) surgeons who reported a total of 117,840 laparoscopic cholecystectomies, 409 incidental gallbladder carcinomas, and 412 laparoscopies on patients with colorectal carcinoma. Altogether 109 patients who developed tumor recurrence in connection with laparoscopic surgery have been reported. Port-site recurrence was identified in 70 of 409 patients (17.1%) with a median of 180 days following laparoscopic cholecystectomy for nonapparent gallbladder carcinoma. In 8 cases (11.5%) a protective plastic bag had been used for gallbladder retrieval. Six patients without port-site metastases were found to have a diffuse peritoneal carcinomatosis a median of 120 days after cholecystectomy. Of 412 laparoscopies for colorectal cancer, 19 cases (4.6%) of tumor seeding have been reported, 16 of which (3.9%) had documented port-site and scar recurrences a median of 196 days after laparoscopy. The tumor specimen was intact, and a plastic bag was used for extraction in seven cases. In 14 patients trocar-site metastases have been reported a median of 70 days after laparoscopy for different nonapparent or known malignancies. The probability of developing abdominal wall metastasis is higher after laparoscopy for cancer than after open surgery. An intact surgical specimen and the use of a plastic retrieval bag do not exclude the risk of port-site recurrences. These facts and the early appearance of peritoneal carcinosis in a few cases of intraabdominal malignancies seem to confirm a specific laparoscopic risk for intraperitoneal tumor cell seeding and implantation.

Adult↗

PubMed1998

Experimental study of the effect of intra-abdominal pressure during laparoscopy on tumour growth and port site metastasis.

BACKGROUND: The influence of raised intraperitoneal pressure during laparoscopy on tumour growth and port site metastasis is still unknown. METHODS: Tumour growth of colonic adenocarcinoma DHD/K12/TRb was measured after laparoscopy with carbon dioxide at different pressures (0, 5, 10 and 15 mmHg) in a rat model. Cell kinetics were determined after incubation with carbon dioxide (0, 5, 10 and 15 mmHg) in vitro (n=60). Additionally, tumour growth was measured subcutaneously and intraperitoneally 4 weeks after laparoscopy at different intraperitoneal pressures (5, 10 and 15 mmHg) (n=100). RESULTS: In vitro tumour growth decreased significantly after incubation with carbon dioxide at 10 and 15 mmHg compared with a pressure of 0 or 5 mmHg. In vivo, mean(s.d.) intraperitoneal tumour weight was significantly increased after laparoscopy at 5 mmHg (919(1085) mg) and at 10 mmHg (1274(1523) mg) (P< 0.05), but decreased again after laparoscopy with an intraperitoneal pressure of 15 mmHg (731(929) mg) compared with the control group (365(353) mg) (P=0.3). Mean(s.d.) subcutaneous tumour growth was promoted after laparoscopy at 5 mmHg (172(234) mg), at 10 mmHg (190(253) mg) and at 15 mmHg (178(194) mg) compared with controls (48(33) mg) (P < 0.05). CONCLUSION: In vitro, raised intraperitoneal pressure leads to suppression of tumour growth. In vivo, intraperitoneal tumour growth is suppressed only by higher pressure (15 mmHg). Subcutaneous tumour growth is stimulated by carbon dioxide independently of the intraperitoneal pressure.

Adenocarcinoma↗

PubMed1997

The "knot before loop" technique for the endoscopic ligation and suture-instrument set. Knot formation and application.

BACKGROUND: In minimally invasive surgery intracorporal knot-tying is complicated by a limited field of vision and depth perception. METHODS: The "knot before loop" technique aims to reduce intraabdominal movements in number and space needed. A grasping instrument 3 mm in diameter guides a slipfit hollow knot pusher with a notch to hold the thread, when extracorporally forming the knot on the instrument tip and an axial slot. The loop is finished under endoscopic vision, yet a second loop is created along the thread. The knot is tightened and secured by closing the second loop without troublesome instrument change. RESULTS: The strength of the knot was tested and the feasibility of the instrument set was proven in pigs and 25 cholecystectomies and hernia repairs in humans. CONCLUSIONS: Endoscopic application of a secured slip knot is simplified by the "knot before loop" technique. The independent formation of the knot by the assisting personnel allows quick application, equivalent to the use of clips and staples. The benefit in cost saving is high.

Feasibility Studies↗

PubMed1997

Laparoscopic cecal ligation and puncture in the rat. Surgical technique and preliminary results.

BACKGROUND: We describe a technique of laparoscopic cecal ligation and puncture (CLP) in the rat analogous to open CLP which may facilitate the study of minimally invasive surgery (MIS) and peritonitis. METHODS: Forty-four rats were randomized to either laparoscopic or open CLP and their 3-day mortality was recorded. Autopsies were performed for peritoneal fluid cultures, measurement of the length of ligated cecum, and scoring of the degree of cecal necrosis. RESULTS: Laparoscopic CLP required slightly longer operating times compared to open CLP (average 15.6 vs 13.1 min, p = 0.002). Three-day postoperative mortality was 36.4% and 22.7% for open and laparoscopic CLP, respectively (p = NS). There were no differences in the length of ligated cecum or the cecal necrosis score between the open and laparoscopic CLP groups. CONCLUSION: Laparoscopic CLP is feasible and produces a fecal peritonitis with similar characteristics to those of traditional open CLP.

Animals↗

PubMed1996

[Instruments for gasless laparoscopic surgery].

Specially designed instruments for laparoscopic surgery with a pneumoperitoneum are expensive and delicate, and surgeons are initially not familiar with their handling. Beside restrictions of the surgeon's intraabdominal range of motion they lead to a loss of tactile sensation. In gasless laparoscopic procedures not only special laparoscopic instruments, but the standard conventional instruments, used in open surgery, can also be employed with simple valveless trocars. Still using these instruments can put up some difficulties, because ergonomic factors were not considered in their development. With regard to the instrument's length, shape and joint-position we developed a special instrument-set under the ergonomic criteria of gasless laparoscopy.

Equipment Design↗

PubMed1995

[Disposable versus reusable instruments in laparoscopic surgery--a controlled study].

The instruments for laparoscopic surgery are usually available in a disposable and in a reusable type. We performed a prospective, randomized study, based on the most frequent laparoscopic operation, the cholecystectomy, in order to directly quantify and compare the advantages and disadvantages of both types of instruments. 158 patients, who planned to undergo a cholecystectomy, were randomly distributed into two groups. 80 patients (group A) underwent surgery with reusable instruments and 78 patients (group B) with disposable instruments. We investigated the following parameters and compared them for both groups: length of operation, complications, conversion rate to open surgery, subjective postoperative pain, length of inability to work, technical problems during operation, postoperative hospitalization time, satisfaction of operating room personnel. The analysis of the results demonstrates no difference in the postoperative hospitalization time, in the postoperative complication rate, subjective pain sensation and postoperative inability to work. Differences in favour for the group of patients, operated with disposable instruments, were found in the conversion rate, in the length of operation and, statistically significant, in the amount of intraoperative problems, caused by instrument-technical reasons. Even if considering the greater expenses in time and personnel costs, operations with reusable instruments are in average 1015 DM cheaper.

Adolescent↗

PubMed1994

[Gasless laparoscopic cholecystectomy].

The pneumoperitoneum as a precondition of laparoscopic procedures represents a restriction of the surgeons freedom of movement and causes rare but typical complications. In July 1993 we started doing laparoscopic cholecystectomy without using a pneumoperitoneum. Under direct vision and digital control the retractor blades are introduced into the abdominal cavity via minilaparotomy. The retractor is attached to an electrically powered mechanical arm and raised. The scope is introduced through the same access and the laparoscopic cholecystectomy can be performed using the established technique without instilling a pneumoperitoneum. Both conventional and laparoscopic surgical instruments were introduced through valveless trocars and unlimited suction without loss of gas and exposure is possible. Metabolic and hemodynamic alterations associated with the intraperitoneal insufflation of carbon dioxide are omitted. So far we did gasless laparoscopic cholecystectomy in 22 patients. We didn't see any related complications. Four times we had to change the surgical procedure. In comparison to the traditional laparoscopic cholecystectomy with a CO2-pneumoperitoneum the results of the first gasless procedures demonstrate possible advantages.

Adult↗