Biomedical subjects
Dan Davis
Publications and source records attributed to Dan Davis.
The learning curve measured by operating times for laparoscopic and open gastric bypass: roles of surgeon's experience, institutional experience, body mass index and fellowship training.
BACKGROUND: Surgeons must overcome a substantial learning curve before mastering laparoscopic Roux-en-Y gastric bypass (LRYGBP). This learning curve can be defined in terms of mortality, morbidity or length of surgery. The aim of this study was to compare the learning curves in terms of surgical time for the first 3 surgeons performing LRYGBP in our hospital with the length of surgery for open gastric bypass (CONTROLS). METHODS: We compared 494 primary LRYGBPs performed by 3 surgeons (393 by 1st SURGEON, 57 by 2nd SURGEON and 44 by 3rd SURGEON) to 159 open vertical banded gastroplasty-Roux-en-Y gastric bypasses (CONTROLS). Data for LRYGBP patients were prospectively obtained. Factors that significantly affected the length of surgery were identified by univariate and multivariate linear regression analysis. RESULTS: LRYGBP and CONTROL patients were similar in age, height, weight and BMI, although more CONTROLS were male. Median time for the 1st SURGEON performing LRYGBP dropped for each subsequent 100 operations: 1st 100 - 190 min, 2nd 100 - 135 min, 3rd 100 - 110 min and 4th 100 - 100 min. Median time for 2nd SURGEON performing LRYGBP was 120 min, 3rd SURGEON 173 min and CONTROLS 64 min. Length of surgery significantly correlated with surgical experience in terms of numbers of operations and BMI of patient. Times for 2nd SURGEON, a fellowship trained laparoscopic surgeon, started significantly faster than 1st SURGEON's, but did not significantly improve with experience. 3rd SURGEON's initial times were similar to 1st SURGEON's, but his times improved more rapidly with experience. Times for CONTROLS were significantly faster than all laparoscopic groups and did not correlate with operation number or patient BMI. CONCLUSIONS: The length of surgery for LRYGBPs continued to shorten beyond 400 operations for the first surgeon performing LRYGBP in our hospital. Previous fellowship training in LRYGBP shortened surgical times during initial clinical experience as an attending for the second surgeon. The learning curve was truncated because of the already established LRYGBP program.
Patient characteristics impacting excess weight loss following laparoscopic adjustable gastric banding.
BACKGROUND: Weight loss is more variable after laparoscopic adjustable gastric banding (LAGB) than after gastric bypass. Subgroup analysis of patients may offer insight into this variability. The aim of our study was to identify preoperative factors that predict outcome. METHODS: Demographics, co-morbid conditions and follow-up weight were collected for our 1st 200 LapBand patients. Linear regression determined average %EWL. Logistic regression analysis identified factors that impacted %EWL. RESULT: 200 patients returned for 778 follow-up visits. Median age was 44 years (21-72) and median BMI 45 kg/m2 (31-76). 140 (80%) were women. Average %EWL was y % = 0.007 %/day (days since surgery) + 0.12% (correlation coef. 0.4823; P<0.001). %EWL at 1 year was 37%. The best-fit logistic regression model found 7 factors that significantly changed the odds of achieving average %EWL. Older patients, diabetic patients and patients with COPD had greater odds of above average %EWL. Female patients, patients with larger BMIs, asthmatic patients and patients with hypertension had increased odds of below average %EWL. CONCLUSION: Specific patient characteristics and comorbid conditions significantly altered the odds of achieving satisfactory %EWL following gastric banding.
Time-domain fluorescence lifetime imaging applied to biological tissue.
Fluorescence lifetime imaging (FLIM) is a functional imaging methodology that can provide information, not only concerning the localisation of specific fluorophores, but also about the local fluorophore environment. It may be implemented in scanning confocal or multi-photon microscopes, or in wide-field microscopes and endoscopes. When applied to tissue autofluorescence, it reveals intrinsic excellent contrast between different types and states of tissue. This article aims to review our recent progress in developing time-domain FLIM technology for microscopy and endoscopy and applying it to biological tissue.