Predicting no-show appointments in a pediatric hospital in Chile using machine learning.

The Chilean public health system serves 74% of the country's population, and 19% of medical appointments are missed on average because of no-shows. The national goal is 15%, which coincides with the average no-show rate reported in the private healthcare system. Our case study, Doctor Luis Calvo Mackenna Hospital, is a public high-complexity pediatric hospital and teaching center in Santiago, Chile. Historically, it has had high no-show rates, up to 29% in certain medical specialties. Using machine learning algorithms to predict no-shows of pediatric patients in terms of demographic, social, and historical variables. To propose and evaluate metrics to assess these models, accounting for the cost-effective impact of possible intervention strategies to reduce no-shows. We analyze the relationship between a no-show and demographic, social, and historical variables, between 2015 and 2018, through the following traditional machine learning algorithms: Random Forest, Logistic Regression, Support Vector Machines, AdaBoost and algorithms to alleviate the problem of class imbalance, such as RUS Boost, Balanced Random Forest, Balanced Bagging and Easy Ensemble. These class imbalances arise from the relatively low number of no-shows to the total number of appointments. Instead of the default thresholds used by each method, we computed alternative ones via the minimization of a weighted average of type I and II errors based on cost-effectiveness criteria. 20.4% of the 395,963 appointments considered presented no-shows, with ophthalmology showing the highest rate among specialties at 29.1%. Patients in the most deprived socioeconomic group according to their insurance type and commune of residence and those in their second infancy had the highest no-show rate. The history of non-attendance is strongly related to future no-shows. An 8-week experimental design measured a decrease in no-shows of 10.3 percentage points when using our reminder strategy compared to a control group. Among the variables analyzed, those related to patients' historical behavior, the reservation delay from the creation of the appointment, and variables that can be associated with the most disadvantaged socioeconomic group, are the most relevant to predict a no-show. Moreover, the introduction of new cost-effective metrics significantly impacts the validity of our prediction models. Using a prototype to call patients with the highest risk of no-shows resulted in a noticeable decrease in the overall no-show rate.

The incorporation of HIV self-testing as an exclusive option among men who have sex with men in Spain: results of an online cross-sectional study.

BACKGROUND: We assessed to what extent HIV self-testing would be incorporated by men who have sex with men (MSM) with previous testing history as their exclusive testing option and describe what actions they would take in the case of obtaining a reactive self-test. METHODS: We conducted an online survey among Spanish resident MSM recruited mainly in gay dating apps and analyze 6171 ever tested individuals. We used Poisson regression to estimate factors associated with the incorporation of self-testing as the exclusive testing option. Among those who would incorporate self-testing as their exclusive option, we described actions taken if obtaining a reactive self-test by number of tests in the past. RESULTS: Nearly half of the participants (48.3%) were > =35 years old, 84.6% were born in Spain, 57.9% had attained a university degree, 55.1% lived in a municipality of ≤500.000 and 86.4% self-identified as homosexual. For 37.2%, self-testing would become their exclusive testing option. The incorporation of self-testing as the exclusive option increased with age 25-34 (PR:1.1, 95%CI:1.0-1.3), 35-44 (PR:1.3, 95%CI:1.2-1.5), 45-49 (PR:1.5, 95%CI:1.3-1.7) and > 50 (PR:1.5, 95%CI:1.3-1.8) and in those who reported unprotected anal intercourse (PR:1.1, 95%CI:1.0-1.2) or having paid for sex (PR:1.2, 95%CI:1.0-1.3) in the last 12 months. It was also associated with having had < 10 HIV test in the past (2-9 tests (PR:1.3, 95%CI:1.1-1.4); 1 test (PR:1.5, 95%CI:1.3-1.7)), and having been tested ≥2 years (PR:1.4, 95%CI:1.3-1.5) or between 1 and 2 years ago (PR:1.1, 95%CI:1.0-1.2). Of participants who would use self-testing exclusively 76.6% would confirm their result in case of obtaining a reactive self-test and only 6.1% wouldn't know how to react. Only one individual expressed that he would do nothing at all. CONCLUSION: HIV self-testing could become the exclusive testing option for more than a third of our participants. It was chosen as the exclusive option especially by older, at risk and under-tested MSM. Self-testing strategies need to especially consider the linkage to care process. In this sense, only a small fraction would not know how to react and virtually nobody reported taking no action if obtaining a reactive result.

Knowledge, actual and potential use of HIV self-sampling testing kits among MSM recruited in eight European countries.

AIM: To describe the knowledge as well as current and potential use of self-sampling kits among men who have sex with men (MSM) and to analyse their preferred biological sample and result communication method. METHODS: We analyse data of MSM of HIV negative or unknown serostatus from an online survey conducted in eight countries (Belgium, Denmark, Germany, Greece, Portugal, Romania, Slovenia and Spain) between April and December 2016. It was advertised mainly in gay dating websites. We conduct a descriptive analysis of the main characteristics of the participants, and present data on indicators of knowledge, use and potential use of HIV self-sampling as well as their preferences regarding blood or saliva sample and face or non-face-to-face result communication by country of residence. RESULTS: A total of 8.226 participants of HIV negative or unknown serostatus were included in the analysis. Overall, 25.5% of participants knew about self-sampling (range: 18.8-47.2%) and 1.1% had used it in the past (range: 0.3-8.9%). Potential use was high, with 66.6% of all participants reporting that they would have already used it if available in the past (range: 62.1-82.1%). Most (78.6%) reported that they would prefer using a blood-based kit, and receiving the result of the test through a non-face-to-face-method (70.8%), even in the case of receiving a reactive result. CONCLUSION: The high potential use reported by MSM recruited in eight different European countries suggests that self-sampling kits are a highly acceptable testing methodology that could contribute to the promotion of HIV testing in this population.

The Effect of Postpartum Depression and Current Mental Health Problems of the Mother on Child Behaviour at Eight Years.

Background Maternal postpartum depression (PPD) could affect children's emotional development, increasing later risk of child psychological problems. The aim of our study was to assess the association between child's emotional and behavioural problems and mother's PPD, considering maternal current mental health problems (CMP). Methods This is a secondary analysis from the EU-Childhood Obesity Project (NCT00338689). Women completed the Edinburgh Postnatal Depression Scale (EPDS) at, 2, 3 and 6 months after delivery and the General Health Questionnaire (GHQ-12) to assess CMP once the children reached the age of 8 years. EPDS scores > 10 were defined as PPD and GHQ-12 scores > 2 were defined as CMP. The psychological problems of the children at the age of eight were collected by mothers through the Child's Behaviour Checklist (CBCL). Results 473, 474 and 459 mothers filled in GHQ-12 and CBCL tests at 8 years and EPDS at 2, 3 and 6 months, respectively. Anxiety and depression was significantly increased by maternal EPDS. Children whose mothers had both PPD and CMP exhibited the highest levels of psychological problems, followed by those whose mothers who had only CMP and only PPD. PPD and CMP had a significant effect on child's total psychological problems (p = 0.033, p < 0.001, respectively). Children whose mothers had PPD did not differ from children whose mothers did not have any depression. Conclusions Maternal postpartum depression and current mental health problems, separately and synergistically, increase children's psychological problems at 8 years.

The rapid test in Spanish pharmacies: a novel programme to reach heterosexual men?

OBJECTIVES: Spain has been a pioneer in the implementation of rapid HIV testing programmes in pharmacies to increase access to testing. However, no formal evaluation of the effectiveness of these programmes has been carried out to date. Our aim was to evaluate the ability of a novel in-pharmacy rapid HIV testing programme to promote diagnosis and reach vulnerable populations. METHODS: Between 2011 and 2012, 2168 people underwent testing in 16 urban pharmacies in 10 cities of a Spanish region with a low prevalence of HIV infection. The main outcomes of the programme were compared with those of the regional surveillance system for new HIV diagnoses (RHSS-CyL). RESULTS: Overall, 52.8% of those tested were heterosexual men, 15.8% were men who have sex with men (MSM) and 25.3% were women. Nine per cent were immigrants and 41.9% were < 30 years old. In total, 59.5% of the heterosexual men, 44.6% of the MSM and 65.3% of the women were previously untested. There were 23 positive results, representing 6% of all new regional diagnoses in 2011. The global prevalence was 1.1% (95% confidence interval 0.6-1.5%) and the prevalence in MSM was 3.8%. Of the reactive results, 60.9% were in MSM, 34.8% in heterosexual men and only 4.3% in women, vs. 35.4%, 37.5% and 15.0%, respectively, reported by the RHSS-CyL. The mean age of those testing positive was 32.7 years vs. 38.7 years in the RHSS-CyL. Fifty per cent of MSM and 75% of heterosexual men testing positive were previously untested. CONCLUSIONS: In Spain, this is the first programme not targeted at the most at-risk populations, and has been shown to be effective in reaching and diagnosing heterosexual men, who are the group most affected by delayed diagnoses. Heterosexual men accounted for over half of those tested and a third of those diagnosed, and most of them were previously untested. Young and previously untested MSM also greatly benefitted from the programme.

Assessment of an outreach street-based HIV rapid testing programme as a strategy to promote early diagnosis: a comparison with two surveillance systems in Spain, 2008-2011.

We assess the added value of a multisite, street-based HIV rapid testing programme by comparing its results to pre-existing services and assessing its potential to reduce ongoing transmission. Between 2008 and 2011, 8,923 individuals underwent testing. We compare outcomes with those of a network of 20 sexually transmitted infections (STI)/HIV clinics (EPI-VIH) and the Spanish National HIV Surveillance System (SNHSS); evaluate whether good visibility prompts testing and assess whether it reaches under-tested populations. 89.2% of the new infections were in men who have sex with men (MSM) vs 78.0% in EPI-VIH and 56.0% in SNHSS. 83.6% of the MSM were linked to care and 20.9% had <350 CD4 HIV prevalence was substantially lower than in EPI-VIH. 56.5% of the HIV-positive MSM tested because they happened to see the programme, 18.4% were previously untested and 26.3% had their last test ≥2 years ago. The programme provided linkage to care and early diagnosis mainly to MSM but attendees presented a lower HIV prevalence than EPI-VIH. From a cost perspective it would benefit from being implemented in locations highly frequented by MSM. Conversely, its good visibility led to reduced periods of undiagnosed infection in a high proportion of MSM who were not testing with the recommended frequency.

[Monitoring steam sterilisation processes in the dental office]. / Het monitoren van stoomsterilisatieprocessen in de mondzorgpraktijk.

In dental offices, steam sterilisation is used to sterilise instruments and in that way to prevent the cross-contamination of patients and the dental team. In order to ensure that the sterilisation process has been executed successfully, every sterilisation process has to be monitored. The monitoring of every load in the steam steriliser is necessary and often even required, either directly (by legislation) or indirectly (by harmonised standards). The complete monitoring protocol consists of controls of the installation, the exposure, the loading, the packaging and, finally, the 'track and trace' of the instruments. For examining the installation, a steam penetration test, such as the Bowie and Dick test, can be carried out.

Awareness and use of nonoccupational HIV post-exposure prophylaxis among people receiving rapid HIV testing in Spain.

OBJECTIVES: This paper examines the awareness and use of nonoccupational HIV post-exposure prophylaxis (nPEP) in Spain, and the factors that influence this awareness. METHODS: Between June 2009 and July 2010, a mobile unit offered free, rapid HIV tests in a number of Spanish cities. A total of 2545 people were passively recruited and tested, and answered a self-administered questionnaire containing sociodemographic, behavioural and nPEP-related questions. Bivariate and multivariate analyses were performed, stratifying by gender/sexual behaviour. RESULTS: Some 34% of the responders were men who have sex with men (MSM), 30% were men who have sex exclusively with women (MSW), and 35% were women. Approximately 26% were foreigners, 46% had a university degree, and 51% had previously taken an HIV test. Overall, 22% were aware of nPEP. Only 2% had ever used it; 70% of these after high-risk sexual intercourse. Awareness was higher among MSM (34%) than women (16%) and MSW (15%). Multivariate analysis showed a lack of nPEP awareness to be associated with being born in Latin America, while awareness increased with the number of previous HIV tests among women and MSW. In MSM, awareness was also associated with having a university degree, the degree of interaction with gay culture, number of partners, and use of the internet as the main way of meeting partners. CONCLUSIONS: nPEP awareness in the studied population was unacceptably low. The promotion of its availability should be made a major objective of prevention programmes, as a complementary measure to condom use.

Stratifying risk outcomes among adult COVID-19 inpatients with high flow oxygen: The R4 score.

BACKGROUND: High flow oxygen therapy (HFO) is a widely used intervention for pulmonary complications. Amid the coronavirus infectious disease 2019 (COVID-19) pandemic, HFO became a popular alternative to conventional oxygen supplementation therapies. Risk stratification tools have been repurposed -and new ones developed- to estimate outcome risks among COVID-19 patients. This study aims to provide a simple risk stratification system to predict invasive mechanical ventilation (IMV) or death among COVID-19 inpatients on HFO. METHODS: Among 529 adult inpatients with COVID-19 pneumonia, we selected unadjusted clinical risk factors for developing the composite endpoint of IMV or death. The risk for the primary outcome by each category was estimated using a Cox proportional hazards model. Bootstrapping was used to validate the results. RESULTS: Age above 62, eGFR under 60 ml/min, room air SpO2 ≤89 % upon admission, history of hypertension, history of diabetes, and any comorbidity (cancer, cardiovascular disease, COPD/ asthma, hypothyroidism, or autoimmune disease) were considered for the score. Each of the six criteria scored 1 point. The score was further simplified into 4 categories: 1) 0 criteria, 2) 1 criterion, 3) 2-3 criteria, and 4) ≥4 criteria. Taking the first category as the reference, risk estimates for the primary endpoint were HR; 2.94 [1.67 - 5.26], 4.08 [2.63 - 7.05], and 6.63 [3.74 - 11.77], respectively. In ROC analysis, the AUC for the model was 0.72. CONCLUSIONS: Our score uses simple criteria to estimate the risk for IMV or death among COVID-19 inpatients with HFO. Higher category reflects consistent increases in risk for the endpoint.

[Identifying and prioritising adverse episodes and failures related to patient safety in Pain Treatment Units]. / Identificación y priorización de episodios adversos y fallos relacionados con la seguridad del paciente en las Unidades de Tratamiento del Dolor.

OBJECTIVES: An expert group coordinated by the Andalusian School of Public Health identified the most serious and frequent adverse events in Pain Treatment Units (PTU), as well the failures and underlying causes, as a prior step to preparing preventive actions. The aims of the project were to identify potential adverse events in Pain Treatment Units, identify failures and their underlying causes, and prioritise these failures according to a failure modes and effects analysis (FMEA) tool. MATERIAL AND METHODS: The method employed consisted of a literature search, the selection of an expert group with experience in PTU, creating a catalogue of adverse events using the generation of ideas technique, and putting the FMEA and Risk Priority Index tools into practice. RESULTS: Up to 66 types of adverse events were identified associated with; medication (30), invasive techniques (15), care process (10), patient information and education (6), and clinical practice (5). It was found that up to 101 failures could be triggered by these adverse events, and that 242 causes could lead to these failures. CONCLUSIONS: The results indicated the need to work principally in two directions, improving the care process in the PTU (the health care organisation), and the professional work, this latter having two aspects, improving the clinical practice, and increase professional skills by means of specific training. Communication, whether inter-professional or inter-department, or with the patient and their family, is identified as a key aspect for improvement.

Difference between both eyes in the calculation of the dioptre power of the intraocular lens in a series of 7994 patients.

PURPOSE: To analyse the distribution of the difference between both eyes in the calculation of the dioptric power of the intraocular lens in a series of 7994 patients and the biometric variables that determine it. METHODS: The data of patients between 3 and 99 years old, residents of the city of Guayaquil and neighbouring sites, who received ocular biometry by partial optical coherence interferometry between 2004 and 2020 were reviewed. Ocular biometrics, including axial length (AL), anterior chamber depth (ACD), and the mean corneal dioptre power (CD), were measured by partial coherence interferometry. Refraction without or with cycloplegia was recorded in spherical equivalent (SE). The Haigis formula from the IOL Master instrument was used to calculate the dioptric power of the intraocular lens in both eyes. RESULTS: Data from the bilateral optical biometry of 7994 patients were analysed. The mean and standard deviation of AL, CD, ACD and dioptre power of the IOL were 23.66 ±â€¯1.25, 43.70 ±â€¯1.49, 3.34 ±â€¯0.40 and +20.46 ±â€¯3.84, respectively. 2538 (31.7%) patients had equal dioptre power of the IOL between both eyes. 3243 (40.6%) patients had a 0.50 D difference; 1162 (14.5%), 1.0 D; 425 (5.3%), 1.5 D. 626 patients (7.8%) had a difference in IOL dioptre of 2 D or more, with a maximum of 24 D. The asymmetry of AL between OU was ≥0.4 mm in 10.49%, while that of CD reached ≥1 D in 1.9%. CONCLUSIONS: 92.16% of patients had a difference within 1.5 D between both eyes in the calculation of the dioptre power of the intraocular lens. In case an eye is programmed in which it is impossible to perform a reliable biometry, either due to trauma or due to white or brunescent cataract, the calculation of the intraocular lens could be done taking as a reference the biometry of the contralateral eye.

No effect of the Penalty Point System on road traffic accident mortality among men with a high socioeconomic status in Spain.

The purpose of this study was to assess the effect of the Penalty Point System (PPS) on road traffic accident mortality by gender and socioeconomic status. We conducted a nationwide prospective study covering adult people living in Spain on November 2001. They were followed up until 30 Nov 2007 to determine vital status and cause of death. An interrupted time-series analysis was used to assess whether PPS (explanatory variable) had both immediate and long-term effect on the rates of road traffic accident mortality (RTAMs) separately by gender. Subjects were classified by socioeconomic status (low and high) using two indicators: educational attainment (up to lower secondary education; upper secondary education or more) and occupation (manual and non-manual workers). We performed several segmented Poisson regression models, controlling for trend, seasonality, 2004 road safety measures and fuel consumption as proxy for traffic exposure. Among men, we found a decrease on the RTAMs immediately after PPS in those with low educational level (16.2 %, IC95 %: 6.1 %-25.2 %) and manual workers (16.3 %, IC95 %: 2.8 %-27.8 %), and a non-significant increase among those with high education level and non-manual workers (6.2 % and 1.8 %). Among women, there were no significant differences in the immediate effect of PPS by socioeconomic status. We did not identify significant trend changes between pre-PPS and post-PPS periods in any socioeconomic group. In a context of downward trend of traffic mortality, the PPS implementation led to an immediate reduction on death rates only among men with a low socioeconomic status.

Long-term impact of the 2008 economic crisis in Spain on road traffic collisions mortality by socioeconomic position.

We aimed to assess the effect of the 2008 crisis on road traffic collision (RTC) mortality in Spain, by socioeconomic position (SEP) and type of road use. This prospective, country-wide study covered all adults living in Spain and aged ≥30 years in November 2001. The long-term effect of the crisis was assessed by measuring the monthly percentage change (MPC) in RTC mortality between the pre-crisis (2002-2007) and crisis period (2008-2011). During the recession, RTC mortality fell more in people with low compared to high SEP, so MPCs difference between periods were of a higher magnitude in the low compared to high SEP groups, especially among men motorcyclists. RTC mortality trends were favorable following the 2008 crisis, particularly among low-SEP groups. In men motorcyclists, the upward trend of the pre-crisis period reversed course.

Time trial exertion traits of cycling's Grand Tours.

We examined 26 professional riders during time trial (TT) competitions of the Grand Tours of cycling (Tour de France and Vuelta Espana; 1997-2003) for the exertional characteristics of contending vs. non-contending (i.e., support) riders. We categorized HR time during TT into training impulse (TRIMP) defined from seasonal VO2max testing [Phase I (RCP]. Races were: Short TT (<15 km; 8.9+/-2.9 km); Individual TT (>15 km; 48.12+/-8.7 km); Uphill TT (20.0+/-8.7 km) and Team TT (44.1+/-20.9 km). We observed statistically significant event-by-contender interactions for all TT (all, P<0.0001) except the short TT. During uphill TT, contenders exerted fewer total TRIMP (P<0.01), more Zone 3 TRIMP (P<0.05), and fewer Zone 2 TRIMP (P<0.01) vs. non-contenders. For individual TT, contenders accumulated more Total and Zone 3 TRIMP vs. non-contenders (all, P<0.05). Interestingly, during the team TT, contenders accumulated more Zone 3, and fewer Zone 2 TRIMP (all, P<0.05), despite having the opportunity to draft behind other riders while in paceline race formation. During TT events, contending riders compete at a level of exertion corresponding to a higher metabolic demand during the uphill TT, individual TT and team TT.

Prevalence of labrum and articular cartilage injuries of the hip on 3T magnetic resonance imaging of asymptomatic elite soccer players. / Prevalencia de lesiones del labrum y del cartílago articular de la cadera en imagen por resonancia magnética simple 3 T de futbolistas profesionales asintomáticos.

OBJECTIVE: To establish the prevalence of lesions of the labrum and articular cartilage of the hip in asymptomatic elite soccer players by performing 3T magnetic resonance imaging. METHODS: Eighty-four asymptomatic hips of 42 professional soccer players were evaluated. Male subjects older than 18 years were included. Cam and pincer deformity were defined as an alpha angle greater than 55 degrees and a lateral centre edge angle greater than 39 degrees, respectively. Labral injuries were classified with the Czerny classification and cartilage damage was classified with the Outerbridge classification. Specific statistical tests were used to establish the relationship between anatomical variances of the hip and the presence of chondral and labral injuries. RESULTS: FAI morphology prevalence was 25%. Abnormalities such as cam (22.5%) and labral injuries (33.8%) were found. Those cases with reported labral injury were predominantly intrasubstance damage (18.8%). Anatomical features of FAI were found to be related to lesions of the femoral cartilage (P<.001), chondrolabral damage (P=.042), or both injuries (P<.001). CONCLUSION: Asymptomatic labral or cartilaginous injuries of the hip were reported in 25% of the included professional soccer players. These injuries were associated with anatomical features of FAI.

Following trends in steam sterilizer performance by quantitative monitoring of non-condensable gases.

Standards require a daily steam penetration test before starting production with a steam sterilizer. In many cases the results of steam penetration tests are not used for improvements or optimization of processes. This study aimed to detect whether trend analysis with an objective and quantifying steam penetration test has added value for the end-user. The databases of an objective quantifying steam penetration test, from the hospital and the manufacturer, are coupled and analysed. In this study, the databases included five steam sterilizers and approximately a four-year period. Based on the analysis, the process of the sterilizers was optimized. The results of the steam penetration tests became more stable over longer periods. This may result in lengthened periods between maintenance and validation. The analysis demonstrates that an objective, quantifying steam penetration test delivers more insights and knowledge of the functioning of the steam sterilization process. This knowledge may be used to optimize the process and reduce costs for the end-user.

Serum concentrations of C reactive protein, alpha1 antitrypsin, and complement (C3, C4, C1 esterase inhibitor) before and during the Vuelta a Espana.

OBJECTIVES: To determine serum concentrations of proinflammatory (C reactive protein, complement C3 and C4) and anti-inflammatory (alpha(1) antitrypsin, C1 esterase inhibitor (C1-INH)) acute phase proteins in elite cyclists before and during a three week cycle tour. METHODS: Seventeen professional cyclists participating in the Vuelta a Espana volunteered for the study. Their mean (SD) physical characteristics were: age 28 (1) years; height 1.7 (0.06) m; weight 65 (7) kg; body fat 7.6 (0.8)%; Vo(2)max 75.3 (2.3) ml/kg/min. Venepuncture was performed on each subject 24 hours before the tour began (T0), on day 11 (the first rest day; T1) and day 21 (the second to last stage of the tour; T2). Samples at T1 and T2 were taken about 17 hours after the previous stage. Analysis of variance was used to determine changes over time. Where significance was found, a Tukey post hoc test was performed. RESULTS: C reactive protein concentrations were consistently within the normal range, although there was a 228%, non-significant increase at T1. C3 concentrations fell within the normal range at all times assessed. C4 concentrations before the race were within the normal range and were significantly increased 10 days (T1) into the race. C1-INH concentrations did not change significantly throughout the race. alpha(1) Antitrypsin concentration before the race was at the lower end of the normal range and was only significantly raised at T2. CONCLUSIONS: Although not as pronounced as those reported in marathon/ultramarathon runners, elite cyclists participating in a three week cycle tour experienced increases in selected proinflammatory and anti-inflammatory acute phase proteins, indicating an acute phase/inflammatory response. It is tenable that the increase in alpha(1) antitrypsin and C1-INH (anti-inflammatory mediators) at T2 served to attenuate the acute phase/inflammatory response. The lower than normal resting concentrations of the acute phase proteins supports the notion that chronic aerobic exercise induces an anti-inflammatory state.

Effect of marker cluster design on the accuracy of human movement analysis using stereophotogrammetry.

This paper presents a new, simple model to evaluate the instrumental random errors in kinematic analysis of human movements using stereophotogrammetry. By means of equations analogous to that relate linear or angular momentum with linear or angular velocities, a direct measurement of instantaneous motion can be made without previous finite displacement analysis. Single explicit expressions can be obtained to evaluate the influence of instrumental random errors in the accuracy of the kinematic variables. From these expressions, some conclusions about the effect of marker cluster design on the experimental errors are obtained. An experiment has been carried out in order to validate the proposed technique and to assess the experimental errors in linear and angular velocity measurement and its influence in instantaneous helical axis determination.

[Complications in laparoscopic nephrectomy]. / Complicaciones de la nefrectomía laparoscópica.

OBJECTIVE: To report the complications and their respective management in our series of laparoscopic nephrectomy. MATERIAL AND METHODS: Between November 1992 and March 2004, 319 patients underwent laparoscopic ablative renal surgery: 152 were women and 167 were men, mean age was 45 years (range: 0,5-82 years). There were 70 radical nephrectomies, 16 radical nephroureterectomies, 63 partial nephrectomies, 124 simples nephrectomies, 15 simples nephroureterectomies, 8 heminephrectomies and 23 living donor nephrectomies. RESULTS: The complication rate was 5.64%. The most frequent complications were bleeding (2.5%) and retroperitoneal haematoma (1.2%). There was not statically difference in complications rate by age, sex, or approach via: transperitoneal versus retroperitoneal. Complication rate was alike with laparoscopic or hand assisted technique. There was not mortality in the series. CONCLUSIONS: We have a low complication rate in laparoscopic nephrectomy. We believe that laparoscopy is a safe technique for patients that require ablative renal surgery when the surgical team has experience in advanced laparoscopic surgery.