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Results for “Learning Curve”

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PubMedDate not supplied

[Peritonectomy and chemohyperthermia in the treatment of peritoneal carcinomatosis: learning curve].

A prospective study has been carried on 37 patients affected by peritoneal carcinomatosis from various primary. Patients have been treated by cytoreductive surgery and intraoperative hyperthermic chemoperfusion. CC 0-1 has been achieved in 81%. The temperature distribution study showed a "barrier effect" with no statistically significant correlation to the survival. Major morbidity and mortality was respectively 37.8% and 16.2%. Two-yr overall survival was 49.1% for all series. Morbidity was significantly directly correlated to the duration of the surgical treatment. A learning curve of 19 months have been observed, after that only one death out 21 procedures has been recorded. Peritoneal carcinomatosis patients, that are submitted to integrated treatment, need a peculiar management that is not comparable to any other in the oncological setting and that requires specific competence.

Carcinoma↗

PubMed1999

Parameter convergence and learning curves for neural networks.

We revisit the oft-studied asymptotic (in sample size) behavior of the parameter or weight estimate returned by any member of a large family of neural network training algorithms. By properly accounting for the characteristic property of neural networks that their empirical and generalization errors possess multiple minima, we rigorously establish conditions under which the parameter estimate converges strongly into the set of minima of the generalization error. Convergence of the parameter estimate to a particular value cannot be guaranteed under our assumptions. We then evaluate the asymptotic distribution of the distance between the parameter estimate and its nearest neighbor among the set of minima of the generalization error. Results on this question have appeared numerous times and generally assert asymptotic normality, the conclusion expected from familiar statistical arguments concerned with maximum likelihood estimators. These conclusions are usually reached on the basis of somewhat informal calculations, although we shall see that the situation is somewhat delicate. The preceding results then provide a derivation of learning curves for generalization and empirical errors that leads to bounds on rates of convergence.

Algorithms↗

PubMed2003

Environmental management by the learning curve.

This is a futuristic appreciation of waste management challenges and their solution by means of good management models. A literature review, administrative initiatives, research results, and experiences from practice are combined in this study to render an evolutionary picture of the change in paradigm relative to municipal solid waste possible to occur between 2000 and 2025. The principal stages of progress in the 25 years studied were: the correct characterization of municipal solid waste as a function of geographical location and recycling potential, the divided collection model and its corresponding learning curve, correct opportunity cost accounting tools, and the generally admitted and accepted changeover of municipal solid waste treatment from a technical to a management problem. It is reported that as a result of this progress, the municipal landfill is a species in extinction. Regional landfills with long life spans are the rule in 2025.

Conservation of Natural Resources↗

PubMed2006

[Right versus left radial artery approach for coronary angiography. Differences observed and the learning curve].

There are anatomical differences between right and left radial artery approaches for coronary catheterization that could influence application of the technique. We present the results of a randomized study that compared the effectiveness of the two approaches and identified factors associated with failure of the procedure. The study involved 351 consecutive patients: a left radial approach was used in 180, and a right radial approach, in 171. The procedure could not be completed using the initial approach selected in 15 patients (11 right radial vs. 4 left radial; P=.007). Use of a right radial approach, lack of catheterization experience, patient age >70 years, and the absence of hypertension were found to be independently associated with prolonged fluoroscopy duration and failure using the initial approach. Use of the right radial approach in patients aged over 70 years was associated with a 6-fold increase in the risk of an adverse event. Consequently, use of the right radial approach should be avoided in patients aged over 70 years when trainee practitioners are on the learning curve.

Age Factors↗

PubMedDate not supplied

The "learning curve" in the performance of laparoscopic cholecystectomy.

Laparoscopic cholecystectomy was successfully performed on 23 of the first 28 patients in whom this was attempted (82.1%). After the first ten cases, the success rate increased to 94.4%. There was only one major complication which prolonged hospital stay but did not require re-operation. Operative time decreased markedly from a mean of 160 minutes for the first ten cases to 61 minutes for the remainder. This increase in operative speed was not accompanied by an increase in complications, in spite of a liberalization of patient selection criteria. It is clear that a steep "learning curve" exists for this procedure and must be recognized and appreciated if laparoscopic cholecystectomy is to become a safe and efficient procedure.

Adult↗

PubMed1999

Total laparoscopic hysterectomy versus total abdominal hysterectomy: an assessment of the learning curve in a prospective randomized study.

The present randomized study was undertaken in order to compare the short-term results between total laparoscopic hysterectomy and abdominal hysterectomy in a centre with experience in laparoscopic surgery. From January 1997 to September 1998 inclusive, 102 women aged 44-71 years were randomly assigned to either total laparoscopic hysterectomy (n = 51 patients) or abdominal hysterectomy (n = 51 patients). The patients' demographic characteristics were similar in both groups. Average intra-operative blood loss was lower in laparoscopic hysterectomy than in abdominal hysterectomy (P </= 0. 001). The average time employed for laparoscopic hysterectomy was 104.1 +/- 26.98 min; according to the learning curve experienced in this study, the range was 72-163 min and the results after the plateau was reached showed no statistical difference between laparoscopic and abdominal operating times. The mean length of hospital stay was 2.38 +/- 0.30 days in the laparoscopic hysterectomy group versus 6.23 +/- 1.85 days in the abdominal hysterectomy group (P </= 0.001). In conclusion, this study shows that total laparoscopic hysterectomy can be effectively performed within reasonable time limits, provided that operators are experienced surgeons in operative laparoscopy and that operating times are comparable with those of abdominal hysterectomy.

Adult↗

PubMed2002

Learning curve for endovascular abdominal aortic aneurysm repair: evaluation of a 277-patient single-center experience.

PURPOSE: To determine the minimum number of stent-graft deployments that an interventional team with endovascular skills must do to be considered well trained in endovascular abdominal aortic aneurysm (AAA) exclusion. METHODS: The records of 277 consecutive patients (236 men; median age 73 years, range 49-91) undergoing endovascular AAA repair at a single institution between 1994 and 1998 were reviewed. Information was collected on procedural success, conversion, time interval between procedures, operative complications, operative mortality, contrast volume, blood loss, intensive care unit (ICU) length of stay (LOS), and hospital LOS. A first-order differential equation was used to calculate a learning curve based on the success rate. Patients were subsequently divided into 5 sequential groups of 55 patients (the last group had 57 patients). RESULTS: Analyzing the pattern of procedural success to failures, a sharp change in the slope was observed between 50 and 65 trials. The number 55 was arbitrarily chosen to represent the point after which the incremental change in the success rate never exceeded 0.01 (<1 failure per 100 attempts). In the intergroup comparisons, success rate (p<0.04), conversion rate (p<0.0001), and procedural frequency (p<0.0001) were statistically significant when the first 55-patient group was compared to the others. Operative complications (p=0.08) and operative mortality (p=0.16) were numerically but not significantly different. Contrast volume was significantly reduced for the last group (p<0.0001). A Cox regression model identified only procedural frequency (p=0.03) and procedural volume (p=0.04) as predictive of technical success. Performing endovascular AAA repairs at a < or =10-day interval was associated with a >80% success rate. CONCLUSIONS: This study shows that not only is the number of procedures important to outcome, but also the frequency with which they are performed. Based on our team's performance data, 55 cases would appear to be the minimum volume and 1 case every 10 days the minimum frequency to obtain good operative results with aortic endografting.

Aged↗

PubMed2003

Ultrasound imaging improves learning curves in obstetric epidural anesthesia: a preliminary study.

PURPOSE: Epidural anesthesia may be difficult in pregnancy. We intended to evaluate the teaching possibilities of ultrasonography as a diagnostic approach to the epidural region. METHODS: Two groups of residents performed their first 60 obstetric epidurals under supervision. One proceeded in the conventional way using the loss of resistance technique (control group = CG). The other group proceeded in the same way but was supported by prepuncture ultrasound imaging, giving them information about the optimal puncture point, depth and angle (ultrasound group = UG). Success was defined as adequate epidural anesthesia requiring a maximum of three attempts, reaching a visual analogue scale score of less than 1, while neither changing the anesthesia technique, nor starting at another vertebral level. In addition, intervention by the supervisor was defined as failure. RESULTS: In the CG we observed a success rate of 60% +/- 16% after the first ten attempts followed by a nearly continuous rise of the learning curve. Within the next 50 epidurals the rate of success increased to 84%. In the UG the rate of success started at 86% +/- 15%. Within 50 epidural insertions it rose up to a level of 94%. The difference between the two groups remained significant (P < 0.001). CONCLUSION: Using ultrasound imaging for teaching epidural anesthesia in obstetrics we found a higher rate of success during the first 60 attempts compared to conventional teaching. We believe this shows the possible value of ultrasound imaging for teaching and learning obstetric regional anesthesia.

Anesthesia, Epidural↗

PubMedDate not supplied

Neonatal hearing screening with transient evoked otoacoustic emissions: a learning curve.

The present paper reports on the implementation of a neonatal hearing screening programme in a private hospital in Belgium. A maternity-based neonatal hearing screening project with transient evoked otoacoustic emissions (TEOAEs) was started in 1993. The cost of the test was not covered by the public health insurance, so the parents had to pay the full cost for screening their child (approximately 30 Euro). Since 1993 the programme strategies have been changed on several occasions to improve the quality and efficacy. A retrospective analysis was performed on: (1) the test pass rate; (2) the coverage; and (3) the number of children who become 'Lost to follow-up' after failing the initial test. The data show a steady learning curve with a time course of several years. They also demonstrate that it is worthwhile and feasible to run a high-quality screening programme in a private establishment.

Belgium↗

PubMed2003

[Lung transplantation results: does a learning curve exist?].

Lung transplantation is an established procedure for end-stage non malignant respiratory disorders. Lung transplantation involves multidisciplinary skills and expertise and one can question the ability of small units to achieve successfully such a demanding therapy. We report here the results from the Lausanne unit of the Geneva-Lausanne lung transplantation center. We have compared the 1993 to 1996 and the 1997-2000 period. For the 29 lung transplantions performed the actuarial survival was 75% at 3 years and 72% at 5 years. There was no significant difference in survival or in functional status between the two periods. We conclude that despite the small number of patients treated, these results compare favourably with published international data. In particular, no learning curve effect was observed.

Adolescent↗

PubMed1995

Ultrasonographic demonstration of normal axillary lymph nodes: a learning curve.

High frequency transducers with near field resolution allow visualization of superficial structures in the axilla, such as the lymph nodes, which could not be visualized with older equipment. We have been able to observe normal axillary nodes in 61.5% of 26 women who had histologic correlation of normal lymph nodes at axillary dissection. We studied 663 women with a clinically palpable breast lump using breast and axillary ultrasonography. They were divided into four groups. The first group consisted of all women who had undergone surgery and had histologic correlation of axillary nodes. The second, third, and fourth groups were made up of three consecutive series of 221 women examined. Women from group one were included in groups two, three, and four. A steep learning curve of 7.1 to 41.9 to 64.7% was observed in the detection of normal axillary nodes, suggesting that these appearances can be recognized easily.

Axilla↗

PubMed2006

[Intraoperative neuromonitoring of the recurrent laryngeal nerve - results and learning curve].

Intraoperative neuromonitoring was introduced in thyroid surgery several years ago resulting in a facilitated identification of the recurrent laryngeal nerve and less recurrent laryngeal nerve injuries. Between 1999 and 2004 data of all patients (n=937) undergoing thyroid resection were recorded prospectively and analyzed yearly. The intraoperative identification of recurrent laryngeal nerve succeeded in 99.2% (1665 nerves at risk). The percentage of completely resecting surgical procedures raised from 17% to 56%. Minimal vocal cord dysfunction associated with hematoma and edema in most cases was diagnosed laryngosopically in 1.4-2.4%. Transient recurrent nerve palsies were seen in 2.3% without changes throughout the years. The permanent palsy rate of 0.8% in the first years decreased. No permanent palsies were diagnosed in the last 3 years. Routine introduction of intraoperative neuromonitoring in thyroid surgery is associated with a demonstrable learning curve lasting several years. Permanent palsy rate is decreased. The rate of minimal vocal cord movement disorders and transient recurrent laryngeal nerve palsies is not changed.

Adult↗

PubMed2001

Defining the learning curve for the Focused Abdominal Sonogram for Trauma (FAST) examination: implications for credentialing.

Focused Abdominal Sonogram for Trauma (FAST) examination is being used increasingly for the torso evaluation of injured patients. In a controlled setting using peritoneal dialysis patients as models for injured patients with free fluid we hypothesized that more experienced providers would perform FAST with greater accuracy. Twelve fellow or attending level trauma surgeons, two radiologists, and one ultrasound technician were studied for their ability to detect intraperitoneal fluid (0-1600 cm3) in nine peritoneal dialysis patients with two different volumes of dialysate/patient. FAST experience with injured patients was defined as minimal (<30 patients examinations), moderate (30-100), or extensive (>100). All surgeons had participated in a didactic/practical course before the study. Test results were reported as "+" or "-" by the participant; "+" results were further quantified by volume. The sensitivity of those in the minimal-, moderate-, and extensive-experience to detect <1 L was 45, 87, and 100 per cent, respectively; the accuracy in detecting dialysate volume within 250 cm3 was 38, 63, and 90 per cent, respectively. In this controlled setting the accuracy of FAST particularly in diagnosing smaller volumes, as well as the ability to quantify volume, improves with experience. The learning curve for FAST starts to flatten out at 30 to 100 examinations. Training and credentialing policies should consider these findings to optimize patient care.

Abdominal Injuries↗

PubMed1989

Echophonocardiography in patients undergoing percutaneous mitral balloon valvotomy (PMV): the learning curve of PMV.

Percutaneous mitral balloon valvotomy (PMV) was performed in 10 female patients with mitral stenosis; their mean age was 31 +/- 1 years. All patients underwent echophonocardiography (Echophono) before and less than 24 hours after PMV1. Cardiac catheterization and Echophono were repeated 10 and 22 months after PMV1. Eight patients with suboptimal results (defined as a post-PMV mitral valve area [MVA]/less than 1.0 cm2 and mean gradient greater than/10 mm Hg) underwent repeat PMV (PMV2) 10 months after PMV1. The Echophono data are correlated with clinical and hemodynamic changes produced by PMV1 and PMV2. MVA increased from 0.6 +/- 0.1 to 1.1 +/- 0.01 cm2 (p = 0.0009) when PMV1 was performed with a mean effective balloon dilating area (EBDA) of 5 +/- 0.19 cm2. MVA increased from 1.0 +/- 0.1 to 1.7 +/- 0.2 cm2 (p = 0.0002) when PMV2 was performed with larger EBDA (6.4 +/- 0.34 cm2). Two factors related to the learning curve account for the superior result of PMV2: (1) use of larger EBDA and (2) optimal position of the balloons parallel to the long axis of the left ventricle. PMV1 resulted in Echophono changes consistent with decreased severity of mitral stenosis: shortening of Q-S1 from 93 +/- 4 to 82 +/- 4 msec (p less than 0.05) and (Q-S1)-(S2-OS) from 1.8 +/- 0.8 to -0.9 +/- 0.6 (p less than 0.01); prolongation of S2-OS from 75 +/- 5 to 91 +/- 5 msec (p less than 0.05) and increase of EF slope from 7 +/- 1 to 17 +/- 4 mm/sec (p less than 0.05). Compared with PMV1, post PMV2 Echophono showed a further decrease in the severity of mitral stenosis: Q-S1 decreased to 78 +/- 3 msec and (Q-S1)-(S2-OS) decreased to -0.5 +/- 0.3 msec. S2-OS increased to 86 +/- 5 msec and EF slope increased to 22 +/- 4 mm/sec. The hemodynamic and Echophono changes produced by PMV1 and PMV2 persisted at the corresponding follow-up studies. There was no evidence of restenosis. Thus Echophono is a simple, low cost method helpful in the evaluation and follow-up of patients undergoing PMV.

Adolescent↗

PubMed2002

Laparoscopic ventral hernia repair during the learning curve.

Large series of laparoscopic ventral hernia repair have shown excellent results. However, published comparative studies have had conflicting outcomes. We retrospectively reviewed the first 29 laparoscopic ventral hernia repairs performed at a VA Medical Center from January 2000 to June 2001. The outcome was compared to that of open repairs performed during the same time period. Outcomes between the groups were similar in all respects, except for the length of stay. The conversion rate for the laparoscopic approach was 13.8%. There was one death in the laparoscopic group due to an unrecognized enterotomy. There were three recurrences in the open group and one in the laparoscopic group with a mean follow up of 13 months. In our series, laparoscopic hernia repair resulted in a shorter hospital stay but no other significant benefits, along with a risk of missed enterotomy. The risk-benefit ratio for this procedure may be high during the learning curve.

Clinical Competence↗

PubMed2002

The learning curve in ambulatory laparoscopic cholecystectomy.

Whether laparoscopic cholecystectomy (LC) should be performed as an outpatient procedure is still under discussion. The aim of this study was to evaluate the influence of surgeon's experience in ambulatory management of LC. Three hundred eighty-one consecutive elective LCs were planned as outpatient procedures. An anesthetic protocol that includes free-opiates anesthesia, preemptive analgesia, and somatovisceral blockade was used. Percentages of ambulatory, overnight, and admitted patients were evaluated, and time series variation was also analyzed. Postoperative pain, nausea and vomiting incidence, postoperative recovery, and complications were examined. Two hundred ninety-one patients were strictly ambulatory (76.3%), 71 (18.6%) required overnight admission, and 19 (4.9%) were admitted. Percentage of ambulatory LC increased from 22% to 90% in 4 years of experience. Readmission rate was 0.01%. Free-opiates anesthetic techniques, preemptive analgesia, and somatovisceral blockade allowed us to obtain over 90% of ambulatory LC. The learning curve related to postoperative evaluation is crucial in obtaining those results.

Adult↗

PubMedDate not supplied

The learning curve in myopic photorefractive keratectomy.

BACKGROUND: The aim of this study was to assess the role of surgeons' skill on the final results of photorefractive keratectomy (PRK) in the correction of myopia. METHODS: We evaluated the results of 160 consecutive unilateral treatments performed by four surgeons in a multicenter study group, with a one year follow up. Eighty-eight patients were males (55%) and 72 females (45%). Mean age was 33.7 years (median = 33, standard deviation = 10.22, range 18-65). Attempted correction ranged between -1.50 and -15.00 D. All the eyes received topical corticosteroid therapy postoperatively. At the one year follow up, we evaluated the following: uncorrected visual acuity lines gained and refractive error (spherical equivalent) as parameters of efficacy and predictability; best spectacle corrected visual acuity loss and corneal clarity as safety parameters. We also examined the centration or decentration of the ablation zone. In order to draw up a kind of learning curve, the mean values for each parameter were calculated by arbitrarily grouping the first 10 cases of each surgeon in the first group (40 patients), the second 10 cases in the second group (40 patients) and so on. RESULTS: We found that increase in uncorrected visual acuity, final refractive error and corneal clarity appeared to improve as the surgeon became more experienced, while loss of best spectacle corrected visual acuity was not significantly influenced by increased surgical experience. CONCLUSIONS: We think experience with photorefractive keratectomy in at least 40 eyes is necessary to obtain best results.

Adolescent↗

PubMed1995

The learning curve for laparoscopic cholecystectomy. The Southern Surgeons Club.

BACKGROUND: The use of laparoscopic surgical procedures without previous training has grown rapidly. At the same time, there have been allegations of increased complications among less experienced surgeons. METHODS: Using multivariate regression analyses, we evaluated the relationship between bile duct injury rate and experience with laparoscopic cholecystectomy for surgeons in the Southern Surgeons Club. RESULTS: Fifty-five surgeons performed 8,839 procedures. Fifteen bile duct injuries (by 13 surgeons) resulted with 90% of the injuries occurring within the first 30 cases performed by an individual surgeon. Multivariate analyses indicated that the only significant factor associated with an adverse outcome was the surgeon's experience with the procedure. A regression model predicted that a surgeon had a 1.7% chance of a bile duct injury occurring in the first case and a 0.17% chance of a bile duct injury at the 50th case. CONCLUSIONS: While surgeons appear to learn this procedure rapidly, institutions might consider requiring surgeons to move beyond the initial learning curve before awarding privileges.

Bile Ducts↗