BIOE 301.ppt

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1、BIOE 301,Lecture Eighteen,Review of Last Time,Sample size calculations Ensure differences between treatment & control group are real Type I Error: (False Positive) Mistakenly conclude there is a difference between the two groups, when in reality there is no difference p-value = probability of making

2、 type I error Type II Error: (False Negative) Mistakenly conclude that there is not a difference between the two, when in reality there is a difference Beta = probability of making type II error Choose our sample size: Acceptable likelihood of Type I or II error Enough $ to carry out the trial,Drug

3、Eluting Stent Sample Size,Treatment group: Receive stent Control group: Get angioplasty Primary Outcome: 1 year restenosis rate Expected Outcomes: Stent: 10% Angioplasty: 45% Error rates: p = .05 Beta = 0.2 SD = 0.78,55 patients required in each arm,Science of Understanding Disease,Emerging Health T

4、echnologies,Preclinical Testing,Clinical Trials,Adoption & Diffusion,Abandoned due to:poor performancesafety concernsethical concernslegal issuessocial issueseconomic issues,Bioengineering,Ethics of research,Cost-Effectiveness,Diffusion is historically slow.,1497: Vasco Da Gama lost 100 out of 160 c

5、rew members to scurvy sailing around Cape of Good Hope 1601: British Navy Captain James Lancaster was in command of 4 ships traveling from England to India Required sailors to take 3 tsp of lemon juice daily on 1 ship The other 3 ships served as the control Results: 110/278 sailors died in control g

6、roup 0 deaths in the experimental group 1747: British Navy Physician James Lind repeated study with similar results 1865: British Navy finally adopted innovation, 264 years after first recorded evidence,Berwick, Donald M., Disseminating Innovations in Health Care. JAMA April 16, 2003 Vol 289, No. 15

7、,Characteristics of people who adopt change,Innovators Mavericks, “willing to leave the village”, weird, incautious, socially disconnected, risk takers Early Adopters Well connected, social opinion leaders, watched by communities Early Majority Local in perspective, follow the lead of the early adop

8、ters Late Majority Watch for local proof Laggards Traditional, prefer the “tried and true”, archivists,Berwick, Donald M., Disseminating Innovations in Health Care. JAMA April 16, 2003 Vol 289, No. 15,Tipping Point often between 15% - 20% adoption; spread becomes difficult to stop.,A Case Study,Chol

9、ecystectomy: Removal of the Gall Bladder,The Gall Bladder,http:/gensurg.co.uk/images/Biliary%20anatomy%20-%20hsk.jpg,The Gall Bladder,Function: Stores bile made by liver After eating: Gall bladder contracts Secretes bile into duct which empties into small intestine Aids in digestion Gallstones: Liqu

10、id bile may precipitate into solid stones Common: 1/5 of North Americans and Europeans develop gallstones at some point,http:/ If gallstones block outflow of bile: Abdominal discomfort Pain Heartburn Indigestion Acute inflammation,http:/ of Gallstones,Before 1990: Open surgery to remove the gall bla

11、dder Effective Low mortality rate (0.3-1.5%) 7 day hospital stay 30 days lost time from work Most common non-obstetric surgical procedure in many countries,A Case Study: Laparoscopic Cholecystectomy,Most significant major surgical advance of the 1980s Allows shorter hospitalization Rapid recovery Ea

12、rly return to work Significant financial savings Forerunner of new era of minimally invasive surgery,Laparoscopic Removal of Gall Bladder,Patient receives general anesthesia Small incision is made at navel and thin tube carrying video camera is inserted Surgeon inflates abdomen with carbon dioxide T

13、wo needle-like instruments inserted; serve as tiny hands. Pick up gallbladder may leave very slight blemishes. Navel incision is barely visible,Laparoscopic Cholecystectomy,http:/ Ease of recovery No incision pain as occurs with standard abdominal surgery Up to 90% of patients go home the same day W

14、ithin several days, normal activities can be resumed No scar on the abdomen Complications: Complication rate is about the same for this procedure as for standard gallbladder surgery: Nausea and vomiting may occur after the surgery Injury to the bile ducts, blood vessels, or intestine can occur, requ

15、iring corrective surgery 5 to 10% of cases, the gallbladder cannot be safely removed by laparoscopy. Standard open abdominal surgery is then immediately performed.,Did this technology diffuse slowly or rapidly?,An Important Innovator,Kurt Semm (1927-2003) Gynecologist 80 medical device inventions El

16、ectronic insufflator Thermocoagulation Loop ligator Laparoscopic suturing Brother and father owned a medical instrument company which rapidly produced instruments for him Allowed more complex procedures to be performed endoscopically Gynecology General surgery,Laparoscopic Appendectomy,1985: Semms t

17、echniques used to perform the worlds first laparoscopic appendectomy Said to reduce problem of adhesions formed during opens surgeries,Public Response,“Hes gone absolutely crazy.” Was asked to undergo a brain scan by his colleagues Lectures were initially greeted with laughter and derision Technique

18、 was initially viewed as too expensive and too dangerous Semm exaggerated problems of adhesions Surgeons saw no reason to change a well established working method into a complex technical manner,Public Response,Semm: “Both surgeons and gynecologists were angry with me. All my initial attempts to pub

19、lish on laparoscopic appendectomy were refused with the comment that such nonsense does not and will never belong to general surgery.” Gynecologists have “surgeon envy” Semm is trying to enter into general surgery to bolster his “operation ego”,Did this technology diffuse slowly or rapidly?,Diffusio

20、n of Lap Choly,http:/www.acponline.org/journals/ecp/marapr99/diffus.pdf,Diffusion of Lap Choly,http:/www.acponline.org/journals/ecp/marapr99/diffus.pdf,Diffusion,No technique in modern times has become so popular as rapidly as laparoscopic cholecystectomy Semm Displayed an ability to push his ideas

21、through despite skepticism and suspicion Without Semm, the laparoscopic revolution may have been postponed by many years,Diffusion of Lap Choly,Diffusion of laparoscopic cholecystectomy in health care is unprecedented Since its introduction in 1989: the laparoscopic procedure has rapidly become the

22、most widely used treatment for gallstone disease By 1992: laparoscopic cholecystectomy accounted for 50% of all cholecystectomies in Medicare populations 75% to 80% of all cholecystectomies in younger populations Increased overall rate of cholecystectomy,Take Home Messages,In most settings: Rate of

23、cholecystectomy increased dramatically after introduction of the laparoscopic procedure Financial incentives for physicians and hospitals to use the procedure influenced the rate of diffusion Introduction of laparoscopic cholecystectomy: Associated with a 22% decrease in the operative mortality rate for cholecystectomy,