Ejemplos de estudios de investigación

1. Ejemplos de estudios de investigación • Comentar algunos ejemplos de interes • Identificar qué tipo de problemas se investigan y el papel del personal de enfermería en estos proyectos • Identificar qué métodos se utilizan para el análisis de resultados • Estadística univariante vs. multivariante

2. The relationship between nurse staffing and patient outcomes.Sasichay-Akkadechanunt T, Scalzi CC, Jawad AF.J Nurs Adm. 2003 Sep;33(9):478-85. Faculty of Nursing, Chiang Mai University, Thailand. thitinut@chiangmai.ac.thOBJECTIVES: To examine the association between in-hospital mortality and four nurse staffing variables-the ratio of total nursing staff to patients, the proportion of RNs to total nursing staff, the mean years of RN experience, and the percentage of nurses with bachelor of science in nursing degrees. BACKGROUND: Studies suggest that nurse staffing changes affect patient and organizational outcomes, but the impact of nurse staffing on patient outcomes has not been studied sufficiently and the results of the previous studies are equivocal. Additionally, the studies of the relationship between nurse staffing and patient outcomes or the impact of nurse staffing on patient outcomes had not been previously examined in Thailand. METHODS: A retrospective, cross-sectional, observational research design was employed to study the research questions. Data of 2531 patients admitted to seven medical units and 10 surgical units of a 2300-bed university hospital in Thailand was used. All data of patients admitted to this hospital with four common groups of principal diagnoses (diseases of the heart, malignant neoplasms [cancer of all forms], hypertension and cerebrovascular diseases, and pneumonia and other diseases of the lung) was extracted from patient charts and discharge summaries in the calendar year 1999. Nurse staffing variables for each nursing unit in 1999 came from nursing service department databases. Multivariate logistic regression was used to determine the relationship between nurse staffing variables and in-hospital mortality. RESULTS: The findings of this study revealed that the ratio of total nurse staffing to patients was significantly related to in-hospital mortality in both partial and marginal analyses, controlling for patient characteristics. In addition, the ratio of total nursing staff to patients was found to be the best predictor of in-hospital mortality among the four nurse staffing variables, controlling for patient characteristics. The study did not find any significant relationship between in-hospital mortality and three nurse staffing variables (the proportion of RNs to total nursing staff, the mean years of RN experience, and the percentage of bachelor degree prepared nurses) probably due to the low variation of these variables across nursing units or because they may have correlated with other variables. CONCLUSIONS: The findings of this study add to our understanding of the importance of nurse staffing and its relationship to the patient outcome of hospital mortality. Further, the findings also provide information for hospital and nursing administrators to use when restructuring the clinical workforce, revising hospital policies, or making contractual decisions on behalf of nursing and public beneficiaries.

3. Men in obstetrical nursing: perceptions of the role.McRae MJ.MCN Am J Matern Child Nurs. 2003 May-Jun;28(3):167-73 School of Nursing, Salem State College, Salem, MA, USA. mrnmcrae@aol.comPURPOSE: To explore the role of men as obstetrical nurses. DESIGN: Exploratory cross sectional survey using structured and open-ended questions. SAMPLE: Three groups: 599 men licensed as Registered Nurses by the Commonwealth of Massachusetts, 337 District I AWHONN members, and 130 pregnant women. ANALYSIS: Univariate, bivariate, and logistic regression were performed for the AWHONN and pregnant women groups. Descriptive and narrative summaries for the men who were Registered Nurses. RESULTS: Seventy-three percent of AWHONN members had positive attitudes toward men in obstetric nursing. The experience of having worked with men in obstetrical nursing roles was the most significant predictor of positive perceptions by AWHONN members. Nurses in the positions of clinical nurse specialists or nurse educators in academia had more negative perceptions of men in this specialty. No predictor variables reached significance for the group of pregnant women. Only 6.8% of the male RNs questioned had ever worked in the specialty, and most reported a lack of interest in working in the specialty of obstetrics. CLINICAL IMPLICATIONS: Findings suggest that both clinical and academic settings may need to adopt more nontraditional recruitment and teaching strategies to encourage men to pursue this specialty.

4. Predictors of nurses' acceptance of an intravenous catheter safety device.Rivers DL, Aday LA, Frankowski RF, Felknor S, White D, Nichols B.Nurs Res. 2003 Jul-Aug;52(4):249-55. BACKGROUND: It is important to determine the factors that predict whether nurses accept and use a new intravenous (IV) safety device because there are approximately 800,000 needlesticks per year with the risk of contracting a life-threatening bloodborne disease such as HIV or hepatitis C. OBJECTIVES: To determine the predictors of nurses' acceptance of the Protectiv Plus IV catheter safety needle device at a teaching hospital in Texas. METHOD: A one-time cross-sectional survey of nurses (N = 742) was conducted using a 34-item questionnaire. A framework was developed identifying organizational and individual predictors of acceptance. The three principal dimensions of acceptance were (a) satisfaction with the device, (b) extent to which the device is always used, and (c) nurse recommendations over other safety devices. Measurements included developing summary subscales for the variables of safety climate and acceptance. Descriptive statistics and multiple linear and logistic regression models were computed. RESULTS: The findings showed widespread acceptance of the device. Nurses who had adequate training and a positive institutional safety climate were more accepting (p <or=.001). Also, nurses who worked at the hospital a shorter period were more likely to be accepting of the device (p <or=.001). Nurses who felt that the safety climate was positive and who had used the device for at least 6 months were more likely to use the device (p <or=.001). DISCUSSION: To achieve maximum success in implementing IV safety programs, high quality training and an atmosphere of caring about nurse safety are required.

5. Evaluation of three types of support surfaces for preventing pressure ulcers in patients in a surgical intensive care unit.Ooka M, Kemp MG, McMyn R, Shott S.J Wound Ostomy Continence Nurs. 1995 Nov;22(6):271-9. Because critical care nurses recognize that many of their patients are at risk for pressure ulcer development, they provide them with support surfaces that can reduce this risk. Few reported studies, however, are available to help these nurses choose these surfaces wisely. This project was a new-product evaluation that compared the clinical effectiveness of three types of support surfaces: two dynamic mattress replacement surfaces and a static foam mattress replacement. Members of a convenience sample of 110 patients admitted to a surgical intensive care unit each used one of the three support surfaces. When each patient was placed on one of the three surfaces, the evaluators rated likelihood of pressure ulcer development (Braden Scale score) and assessed the skin for pressure ulcers. The evaluators repeated the Braden Scale score weekly and the skin assessment three times each week. Nine patients (8%), three patients on each support surface, acquired pressure ulcers. The log-rank test did not find a statistically significant difference between the three types of support surfaces with respect to the risk of pressure ulcer development. Stepwise Cox proportional hazards regression revealed a statistically significant relationship between the risk of developing a pressure ulcer, the averaged total Braden Scale score, and the averaged score for the sensory perception subscale of the Braden Scale. Although these three surfaces were comparable in effectiveness, they were not comparable in cost. Both dynamic mattress replacement surfaces cost approximately $2000 each, whereas the cost of the static foam mattress replacement was only $240 each. The results of this product evaluation should encourage other nurses to evaluate patient care products carefully before making recommendations.

6. A randomized, controlled trial of protocol-directed versus physician-directed weaning from mechanical ventilation.Kollef MH, Shapiro SD, Silver P, St John RE, Prentice D, Sauer S, Ahrens TS, Shannon W, Baker-Clinkscale D.Crit Care Med. 1997 Apr;25(4):567-74. OBJECTIVE: To compare a practice of protocol-directed weaning from mechanical ventilation implemented by nurses and respiratory therapists with traditional physician-directed weaning. DESIGN: Randomized, controlled trial. SETTING: Medical and surgical intensive care units in two university-affiliated teaching hospitals. PATIENTS: Patients requiring mechanical ventilation (n = 357). INTERVENTIONS: Patients were randomly assigned to receive either protocol-directed (n = 179) or physician-directed (n = 178) weaning from mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: The primary outcome measure was the duration of mechanical ventilation from tracheal intubation until discontinuation of mechanical ventilation. Other outcome measures included need for reintubation, length of hospital stay, hospital mortality rate, and hospital costs. The median duration of mechanical ventilation was 35 hrs for the protocol-directed group (first quartile 15 hrs; third quartile 114 hrs) compared with 44 hrs for the physician-directed group (first quartile 21 hrs; third quartile 209 hrs). Kaplan-Meier analysis demonstrated that patients randomized to protocol-directed weaning had significantly shorter durations of mechanical ventilation compared with patients randomized to physician-directed weaning (chi 2 = 3.62, p = .057, log-rank test; chi 2 = 5.12, p = .024, Wilcoxon test). Cox proportional-hazards regression analysis, adjusting for other covariates, showed that the rate of successful weaning was significantly greater for patients receiving protocol-directed weaning compared with patients receiving physician-directed weaning (risk ratio 1.31; 95% confidence interval 1.15 to 1.50; p = .039). The hospital mortality rates for the two treatment groups were similar (protocol-directed 22.3% vs. physician-directed 23.6%; p = .779). Hospital cost savings for patients in the protocol-directed group were $42,960 compared with hospital costs for patients in the physician-directed group.CONCLUSION: Protocol-guided weaning of mechanical ventilation, as performed by nurses and respiratory therapists, is safe and led to extubation more rapidly than physician-directed weaning.

7. The role of support surfaces and patient attributes in preventing pressure ulcers in elderly patients.Kemp MG, Kopanke D, Tordecilla L, Fogg L, Shott S, Matthiesen V, Johnson B. • Res Nurs Health. 1993 Apr;16(2):89-96. • Nurses caring for elderly patients often need to select support surfaces that reduce the likelihood of pressure ulcers, but there is little information about the effectiveness of different support surfaces. This randomized trial compared two support surfaces and investigated patient attributes related to the risk of developing a pressure ulcer. Eighty-four elderly patients were nursed on a convoluted or solid foam overlay and assessed three times a week for pressure ulcers. Stepwise Cox proportional hazards regression revealed a statistically significant relationship between the risk of developing a pressure ulcer and the variables mobility and type of support surface.

8. Terminal cancer. duration and prediction of survival time.Llobera J, Esteva M, Rifa J, Benito E, Terrasa J, Rojas C, Pons O, Catalan G, Avella A.Unitat d'Investigacio, Atencic primaria de Mallorca, Insalud Balears, • Eur J Cancer. 2000 Oct;36(16):2036-43. The duration of the terminal period of cancer allows us to determine its prevalence, which is necessary to plan palliative care services. Clinical prediction of survival influences access to palliative care and the healthcare approach to be adopted. The objective of this study was to determine the duration of the terminal period, the prognostic ability of healthcare professionals to predict this terminal period and the factors that can improve the prognostic accuracy. In the island of Mallorca, Spain, we followed 200 cancer patients at the inception of the terminal period. Twenty-one symptoms, quality of life, prognosis and duration of survival were measured. Using a Cox regression model, a predictive survival model was built. Median duration was 59 days; 95% confidence interval (CI)=49-69 days, mean=99 days. The oncologists were accurate in their predictions (+/-1/3 duration) in 25.7% of cases, the nurses in 21.5% of cases and the family physicians in 21.7% of cases. Errors of overestimation occurred 2.86-4.14 times more frequently than underestimation. In the final model, in addition to clinical prognosis (P=0.0094), asthenia (P=0.0257) and the Hebrew Rehabilitation Centre for Aged Quality of Life (HRCA-QL) Index (P=0.0002) were shown to be independent predictors of survival. In this study, the estimated duration of the terminal period was greater than that reported in a series of palliative care programmes, and survival was overestimated. Oncologists could estimate prognosis more accurately if they also take into account asthenia and HRCA-QL Index.

9. Terminal cancer:duration and prediction of survival time. Análisis de supervivencia Kaplan-Meier Regresión de Cox

10. Terminal cancer: duration and prediction of survival time.

11. Terminal cancer: duration and prediction of survival time. Curvas de supervivencia

12. Terminal cancer: duration and prediction of survival time. This study pinpoints the need for a more accurate estimation of the duration of the terminal period, based on more precise definitions of its onset. Knowing the duration of the terminal period will make it possible to establish the prevalence of terminal cases (essential information for planning palliative care). Prospective studies are a good alternative to retrospective studies, although there are dificulties in carrying them out that can only be overcome through collaboration with primary care services. The study also showed the inaccuracy of clinical predictions of survival. For that reason, it is inadvisable to use these predictions as the sole criterion for the inclusion of patients in palliative care programmes, although they do provide useful information for planning care, especially if they are based on the presence of asthenia and other symptoms with statistically demonstrated predictive value. Finally, the study revealed that quality of life scores such as the HRCA-QL can be useful tools for reducing prognostic uncertainty.

13. Effectiveness of counselling patients on physical activity in general practice: cluster randomised controlled trialC Raina Elley, Ngaire Kerse, Bruce Arroll, Elizabeth Robinson BMJ VOLUME 326 12 APRIL 2003 Objective To assess the long term effectiveness of the “green prescription” programme, a clinician based initiative in general practice that provides counselling on physical activity. Intervention General practitioners were prompted by the patient to give oral and written advice on physical activity during usual consultations. Exercise specialists continued support by telephone and post. Control patients received usual care.

14. Effectiveness of counselling patients on physical activity in general practice: cluster randomised controlled trial Results 74% (117/159) of general practitioners and 66% (878/1322) of screened eligible patients participated in the study. The follow up rate was 85% (750/878). Mean total energy expenditure increased by 9.4 kcal/kg/week (P=0.001) and leisure exercise by 2.7 kcal/kg/week (P=0.02) or 34 minutes/week more in the intervention group than in the control group (P=0.04). The proportion of the intervention group undertaking 2.5 hours/week of leisure exercise increased by 9.72% (P=0.003) more than in the control group (number needed to treat=10.3). SF-36 measures of self rated “general health,” “role physical,” “vitality,” and “bodily pain” improved significantly more in the intervention group (P < 0.05). A trend towards decreasing blood pressure became apparent but no significant difference in four year risk of coronary heart disease. Conclusion Counselling patients in general practice on exercise is effective in increasing physical activity and improving quality of life over 12 months.

15. Effectiveness of counselling patients on physical activity in general practice: cluster randomised controlled trial Design We used a cluster randomised controlled trial design. We stratified participating general practices by size and computer randomised them at a distant site before recruiting patients. Rolling recruitment of patients from each practice was spread evenly from April 2000 to April 2001. Researchers spent one week at each practice enrolling patients and completing baseline assessments.

16. The “green prescription” intervention • Primary care clinicians are offered four hours of training in how to use motivational interviewing techniques to give advice on physical activity and the green prescription • Patients who have been identified as “less active” through screening at the reception desk and who agree to participate receive a prompt card, stating their stage of change, from the researcher, to give to the general practitioner during consultation • In the consultation, the primary care professional discusses increasing physical activity and decides on appropriate goals with the patient. These goal, usually home based physical activity or walking, are written on a standard green prescription and given to the patient • A copy of the green prescription is faxed to the local sports foundation with the patient’s consent. Relevant details such as age, weight, and particular health conditions are often included • Exercise specialists from the sports foundation make at least three telephone calls (lasting 10-20 minutes) to the patients over the next three months to encourage and support them. Motivational interviewing techniques are used. Specific advice about exercise or community groups is provided if appropriate • Quarterly newsletters from the sports foundations about physical activity initiatives in the community and motivational material are sent to participants. Other mailed materials, such as specific exercise programmes, are sent to interested participants • The staff of the general practice is encouraged to provide feedback to the participant on subsequent visits to the practice

17. Fase de diseño del estudio Sample size calculation A sample size of 800 patients from 40 practices (=0.05, power=90%) was required to detect differences in change between the intervention and control groups of one hour of moderate physical activity per week, 4.5 mm Hg systolic blood pressure, 10% relative risk of cardiovascular events, and six points of SF-36 “vitality.” We assumed an attrition rate of 25%. To account for the effect of clustering, we adjusted the sample size calculations by using intraclass correlation coefficients of 0.05, 0.016, 0.0036, and 0.05 for physical activity, blood pressure, cardiovascular risk, and “vitality,” respectively, based on estimates from previous studies.9–11

22. Analysis We used a self report questionnaire from the Auckland heart study to record duration, frequency, and intensity of physical activities and rest during leisure time, occupation, at home, and during transport. We used an empirically based compendium to calculate expenditure of energy during leisure time and in total (kcal/kg/week). We calculated four year risk of coronary heart disease for participants under 75 years of age, using the Framingham equation for participants without previous cardiovascular disease and the D’Agostino equation for participants with previous cardiovascular disease. We carried out the coding and double data entry using Microsoft Access (1997).We analysed differences between intervention and control groups in change of outcome variables by using random effects models in Stata 7.0 (generalised least squares) and SAS 8.2 (mixed model), to allow for clustering by practice. All outcome analyses were by intention to treat, according to random allocation. We adopted a conservative method whereby baseline observations were carried forward for missing data of all outcome variables except four year risk of coronary heart disease. For this variable, mean increase in risk in the control population was used for participants who failed to attend follow up. We adjusted analysis of blood pressure for changes in medication.

23. Métodos estadísticos • Descriptiva • Gráficas y tablas • Estimación • Proporciones y medias • Diferencia entre grupos • Riesgo relativo (odds ratio) • Multivariante • Regresión logística • Análisis de la varianza • Análisis de supervivencia (Regresión de Cox) • ……

24. Estadística univarianteMétodos en función de los objetivos • Comparar grupos (cualitativo) • Comparar proporciones • Estimar riesgo relativo • Comparar si dos grupos tienen la misma proporción de mejoras • Comparar características de dos grupos • Evaluar criterios diagnóstico • Análisis de tablas • Estimación de diferencia de proporciones, riesgo relativo, …

25. Estadística univarianteMétodos en función de los objetivos • Comparar grupos (cuantitativo) • Comparar medias • Evaluar tratamientos • Comparar si dos grupos tienen la misma media de un determinado parámetro clínico • Comparar características de dos grupos • Evaluar ensayos clínicos • Estimación de diferencia de medias, análisis de la varianza

26. Estadística multivarianteMétodos en función de los objetivos • Predicción de una probabilidad en función de distintas variables • Estudiar qué factores de riesgo influyen en la probabilidad de un determinado suceos • Estimar riesgos relativos y ajustar en función de variables de confusión • Estimar la probabilidad de un suceso (muerte, enfermedad, complicaciones) en función de diversas variables • Variables predictoras • Determinan la probabilidad • Variables de confusión • Deben tenerse en cuenta para estandarizar resultados • Regresión logística, redes neuronales

27. Estadística multivarianteMétodos en función de los objetivos • Predicción de una variable cuantitativa en función de distintas variables (cuantitativas) • Estudiar de qué dependen los valores de un determinado parámetro clínico • Estimar valores de una variable en función de otras variables • Estimar el peso ideal de una persona en función de la edad, la altura y otros factores determinantes • Variables predictoras • Determinan los valores • Variables de confusión • Deben tenerse en cuenta para estandarizar resultados • Regresión múltiple, modelo general lineal, regresión no-lineal, estimación no-paramétrica de curvas estándard

28. Estadística multivarianteMétodos en función de los objetivos • Predicción de la supervivencia • Estudiar de qué depende la supervivencia de un determinado tipo de pacientes • Estimar la supervivencia en función de distintos factores • Identificar factores de riesgo • Comparar grupos • Determinar qué factores determinan una mejor evolución en un determinado tratamiento • Variables predictoras • Determinan los valores • Variables de confusión • Deben tenerse en cuenta para estandarizar resultados • Análisis de supervivencia