BIOE 301 group are real Type I Error: (False Positive) Mistakenly - PDF document

Review of Last Time � Sample size calculations � Ensure differences between treatment & control BIOE 301 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 type I error � Type II Error: (False Negative) Lecture Eighteen � 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 Science of Drug Eluting Stent – Sample Size Understanding Disease Emerging Health � Treatment group: Technologies � Receive stent Bioengineering � Control group: 55 � Get angioplasty patients � Primary Outcome: required Preclinical Testing in each � 1 year restenosis rate Ethics of research arm � Expected Outcomes: Adoption & Clinical Trials Diffusion Abandoned due to: � Stent: 10% Cost-Effectiveness • poor performance � Angioplasty: 45% • safety concerns • ethical concerns � Error rates: • legal issues • social issues � p = .05 • economic issues � Beta = 0.2 � SD = 0.78 Diffusion is historically slow…. Characteristics of people who adopt change � 1497: � Vasco Da Gama lost 100 out of 160 crew members to scurvy sailing Innovators � around Cape of Good Hope Mavericks, “willing to leave � � 1601: the village”, weird, incautious, socially � British Navy Captain James Lancaster was in command of 4 ships disconnected, risk takers traveling from England to India Early Adopters � � Required sailors to take 3 tsp of lemon juice daily on 1 ship Well connected, social � � The other 3 ships served as the control opinion leaders, watched by communities � Results: � Early Majority � 110/278 sailors died in control group � Local in perspective, follow � 0 deaths in the experimental group the lead of the early adopters � 1747: Late Majority � � British Navy Physician James Lind repeated study with similar results Watch for local proof � � 1865: Laggards � Tipping Point – often between 15% - 20% � British Navy finally adopted innovation, 264 years after first � Traditional, prefer the recorded evidence “tried and true”, archivists adoption; spread becomes difficult to stop. Berwick, Donald M., Disseminating Innovations in Health Care. JAMA April 16, 2003 – Vol 289, No. 15 Berwick, Donald M., Disseminating Innovations in Health Care. JAMA April 16, 2003 – Vol 289, No. 15

The Gall Bladder http://gensurg.co.uk/images/Bil iary%20anatomy%20- %20hsk.jpg A Case Study Cholecystectomy: Removal of the Gall Bladder The Gall Bladder Gallstones � Function: � Symptoms � Stores bile made by liver � After eating: � If gallstones block outflow of bile: � Gall bladder contracts � Abdominal discomfort � Secretes bile into duct which empties into small intestine � Pain � Aids in digestion � Heartburn � Gallstones: � Indigestion � Liquid bile may precipitate into solid stones � Acute inflammation � Common: � 1/5 of North Americans and ¼ Europeans develop gallstones at some point http://www.qualitysurgical.com/gblad.jpg http://www.thaiclinic.com/images/biliary_anatomy.gif A Case Study: Treatment of Gallstones Laparoscopic Cholecystectomy � Before 1990: � Most significant major surgical advance of � Open surgery to remove the gall bladder the 1980s � Effective � Allows shorter hospitalization � Low mortality rate (0.3-1.5%) � Rapid recovery � 7 day hospital stay � 30 days lost time from work � Early return to work � Most common non-obstetric surgical � Significant financial savings procedure in many countries � Forerunner of new era of minimally invasive surgery

Laparoscopic Removal of Gall Bladder Laparoscopic Cholecystectomy � Patient receives general anesthesia � Small incision is made at navel and thin tube carrying video camera is inserted � Surgeon inflates abdomen with carbon dioxide � Two needle-like instruments inserted; serve as tiny hands. Pick up gallbladder & move intestines around. � Several instruments inserted to clip gallbladder artery & bile duct, to safely dissect & remove gallbladder & http://www.lapsurgery.com/gallblad.jpg stones � Gallbladder is teased out of tiny navel incision. � http://www.laparoscopy.com/pictures/lap_chol.h � Entire procedure normally takes 30 to 60 minutes. tml � Three puncture wounds require no stitches; may leave very slight blemishes. Navel incision is barely visible Advantages/Disadvantages � Benefits: � Ease of recovery Did this technology � No incision pain as occurs with standard abdominal surgery � Up to 90% of patients go home the same day diffuse slowly or rapidly? � Within 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, requiring corrective surgery � 5 to 10% of cases, the gallbladder cannot be safely removed by laparoscopy. Standard open abdominal surgery is then immediately performed. An Important Innovator Laparoscopic Appendectomy � Kurt Semm (1927-2003) � 1985: � Gynecologist � Semm’s techniques used to perform the � 80 medical device inventions world’s first laparoscopic appendectomy � Electronic insufflator � Said to reduce problem of adhesions formed � Thermocoagulation during opens surgeries � 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

Public Response Public Response � “He’s gone absolutely crazy.” � Semm: � Was asked to undergo a brain scan by his � “Both surgeons and gynecologists were angry colleagues with me. All my initial attempts to publish on laparoscopic appendectomy were refused with � Lectures were initially greeted with the comment that such nonsense does not laughter and derision and will never belong to general surgery.” � Technique was initially viewed as too expensive and too dangerous � Gynecologists have “surgeon envy” � Semm exaggerated problems of adhesions � Semm is trying to enter into general � Surgeons saw no reason to change a well surgery to bolster his “operation ego” established working method into a complex technical manner Diffusion of Lap Choly Did this technology diffuse slowly or rapidly? http://www.a cponline.org/j ournals/ecp/ marapr99/diff us.pdf Diffusion of Lap Choly Diffusion � No technique in modern times has become so popular as rapidly as laparoscopic cholecystectomy � Semm � Displayed an ability to push his ideas through despite skepticism and suspicion � Without Semm, the laparoscopic revolution may have been postponed by many years http://www.acpon line.org/journals/e cp/marapr99/diffu s.pdf

Diffusion of Lap Choly Take Home Messages � In most settings: � Diffusion of laparoscopic cholecystectomy in health care is unprecedented � Rate of cholecystectomy increased dramatically after introduction of the � Since its introduction in 1989: laparoscopic procedure � the laparoscopic procedure has rapidly become the � Financial incentives for physicians and most widely used treatment for gallstone disease hospitals to use the procedure influenced � By 1992: the rate of diffusion � laparoscopic cholecystectomy accounted for 50% of all cholecystectomies in Medicare populations � Introduction of laparoscopic � 75% to 80% of all cholecystectomies in younger cholecystectomy: populations � Associated with a 22% decrease in the � Increased overall rate of cholecystectomy operative mortality rate for cholecystectomy