Explicit guidelines for qualitative research: a step in the right direction, a defence of the 'soft' option, or a form of sociological imperialism?
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Within the context of health service research, qualitative research has sometimes been seen as a 'soft' approach, lacking scientific rigour. In order to promote the legitimacy of using qualitative methodology in this field, numerous social scientists have produced checklists, guidelines or manuals for researchers to follow when conducting and writing up qualitative work. However, those working in the health service should be aware that social scientists are not all in agreement about the way in which qualitative work should be conducted, and they should not be discouraged from conducting qualitative research simply because they do not possess certain technical skills or extensive training in sociology, anthropology or psychology. The proliferation of guidelines and checklists may be off-putting to people who want to undertake this sort of research, and they may also make it even more difficult for researchers to publish work in medical journals. Consequently, the very people who may be in a position to change medical practice may never read the results of important qualitative research. (+info)
Reciprocal ST-segment depression associated with exercise-induced ST-segment elevation indicates residual viability after myocardial infarction.
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OBJECTIVES: We evaluated the clinical significance of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability within the infarcted area. BACKGROUND: Although the relation between residual viability and exercise-induced ST-segment elevation has been described, there are no reports focusing on the relation between myocardial viability and reciprocal ST-segment depression associated with exercise-induced ST-segment elevation. METHODS: We evaluated regional blood flow and glucose utilization using N-13 ammonia (NH3) and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in 30 patients with a previous Q-wave myocardial infarction (anterior in 15, inferior in 15). All subjects had single-vessel disease and had exercise-induced ST-segment elevations (> or =1 mm) in electrocardiographic leads. RESULTS: Reciprocal ST-segment depression (> or =1 mm) was present in 16 patients (Group A; anterior in 6, inferior in 10) but not in the remaining 14 patients (Group B). The degree of exercise-induced ST-segment elevation (1.8+/-0.2 vs. 2.0+/-0.2 mm) and the time from the onset of infarction to the study (75+/-49 vs. 74+/-52 days) did not differ between groups. There were no significant differences between groups in the severity of left ventricular dysfunction and the residual luminal narrowing in the infarct-related artery (45+/-21 vs. 48+/-25%). The presence and site of infarction were confirmed by NH3-PET in all patients. FDG-PET demonstrated residual tissue viability within infarct-related area in all patients in Group A and in 3 (21%) of 14 patients in Group B (p < 0.01). The sensitivity, specificity and accuracy of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability were 84%, 100% and 90%, respectively. CONCLUSIONS: The occurrence of reciprocal ST-segment depression associated with exercise-induced ST segment elevation in patients with a previous Q-wave infarction who had single-vessel disease indicates residual tissue viability within the infarct-related area. (+info)
Quantification of collateral flow in humans: a comparison of angiographic, electrocardiographic and hemodynamic variables.
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OBJECTIVES: Evaluation of collateral vascular circulation according to hemodynamic variables and its relation to myocardial ischemia. BACKGROUND: There is limited information regarding the hemodynamic quantification of recruitable collateral vessels. METHODS: Angiography of the donor coronary artery was performed before and during balloon coronary occlusion in 63 patients with one vessel disease. Patients were divided into groups of those with an absence of collateral vessels (group 1, n = 10), those with recruitable collateral vessels (group 2, n = 23) and those with spontaneously visible collateral vessels (group 3, n = 30). During balloon inflation the coronary wedge/aortic pressure ratio (Pw/Pao) was determined as were collateral blood flow velocity variables, using a 0.014" Doppler guide wire. Myocardial ischemia was defined as > or =0.1 mV ST-shift on a 12 lead electrocardiogram at 1 min coronary occlusion. RESULTS: Myocardial ischemia was present in all patients of group 1, in 14 patients of group 2 and in 3 patients of group 3. Recruitable collateral flow without ischemia showed similar hemodynamic values as in group 3 while these values were similar to group 1 in regard to the presence of recruitable collateral vessels showing ischemia. Logistic regression analysis revealed both Pw/Pao and Vi(col) as independent predictors for the function of collateral vessels. CONCLUSIONS: Hemodynamic variables of collateral vascular circulation are better markers of the functional significance of collateral vessels than is coronary angiography. The total collateral blood flow velocity integral and coronary wedge/aortic pressure ratio are good and independent predictors of the function of collateral vessels producing complementary information. (+info)
OBJECTIVES: The purpose of this study is to validate the use of tissue Doppler acceleration imaging (TDAI) for evaluation of the onset of ventricular contraction in humans. BACKGROUND: Tissue Doppler acceleration imaging can display the distribution, direction and value of ventricular acceleration responses to myocardial contraction and electrical excitation. METHODS: Twenty normal volunteers underwent TDAI testing to determine the normal onset of ventricular acceleration. Two patients with paroxysmal supraventricular tachycardia and 30 patients with permanent pacemakers underwent introduction of esophageal and right ventricular pacing electrodes, respectively, and were studied to visualize the onset of pacer-induced ventricular acceleration. Eight patients with dual atrioventricular (AV) node and 20 patients with Wolff-Parkinson-White (WPW) syndrome underwent TDAI testing to localize the abnormal onset of ventricular acceleration, and the results were compared with those of intracardiac electrophysiology (ICEP) tests. RESULTS: The normal onset and the onset of dual AV node were localized at the upper interventricular septum (IVS) under the right coronary cusp within 25 ms before the beginning of the R wave in the electrocardiogram (ECG). In all patients in the pacing group, the location and timing of the onset conformed to the positions and timing of electrodes (100%). In patients with WPW syndrome, abnormal onset was localized to portions of the ventricular wall other than the upper IVS at the delta wave or within 25 ms after the delta wave in the ECG. The agreement was 90% (18 of 20) between the abnormal onset and the position of the accessory pathways determined by ICEP testing. CONCLUSIONS: These results suggest that TDAI is a useful noninvasive method that frequently is successful in visualizing the intramural site of origin of ventricular mechanical contraction. (+info)
Improved accuracy and precision of thermodilution cardiac output measurement using a dual thermistor catheter system.
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OBJECTIVES: To assess whether thermodilution cardiac output determination based on measurement of injectate temperature in vivo leads to more accurate and precise estimates and to study the influence of chilled injectate on test performance. BACKGROUND: Cardiac output measurement via right heart catheterization is used extensively for hemodynamic evaluation in a variety of diagnostic, perioperative and critical care settings. Maximizing accuracy is essential for optimal patient care. METHODS: This prospective study of 960 thermodilution cardiac output measurements was conducted using conventional and dual thermistor techniques. Specialized dual thermistor right heart catheters were constructed using a second thermistor positioned to measure injectate temperature in vivo just prior to entry into the right atrium. To eliminate interinjection variability, a custom set-up was developed that permitted output measurement using both techniques simultaneously. Both ambient temperature injections and cooled injections were investigated. RESULTS: The dual thermistor technique demonstrated significantly less measurement variability than the conventional technique for both ambient temperature (precision = 0.41 vs. 0.55 L/min, p < 0.001) and cooled (precision = 0.35 vs. 0.43 L/min, p = 0.01) injections. Similarly, the average range of cardiac output values obtained during five sequential injections in each patient was less using the dual thermistor approach (1.05 vs. 1.55 L/min, p < 0.001). The use of cooled injectate reduced the mean error of the dual thermistor technique but actually increased the mean error of the conventional technique. Even with ambient temperature injections, injectate warming during catheter transit varied considerably and unpredictably from injection to injection (2 SD range = -0.22 to 5.74 degrees C). Conventional ambient temperature and cooled measurements significantly overestimated Fick cardiac output measurements by 0.32 and 0.50 L/min, respectively (p < 0.001). In contrast, dual thermistor measurements were statistically similar (-0.08 and -0.08 L/min, p = 0.34) to Fick measurements. CONCLUSIONS: This new dual thermistor approach results in a significant improvement in both precision and accuracy of thermodilution cardiac output measurement. (+info)
The association between sleep apnea and the risk of traffic accidents. Cooperative Group Burgos-Santander.
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BACKGROUND AND METHODS: Drowsiness and lack of concentration may contribute to traffic accidents. We conducted a case-control study of the relation between sleep apnea and the risk of traffic accidents. The case patients were 102 drivers who received emergency treatment at hospitals in Burgos or Santander, Spain, after highway traffic accidents between April and December 1995. The controls were 152 patients randomly selected from primary care centers in the same cities and matched with the case patients for age and sex. Respiratory polygraphy was used to screen the patients for sleep apnea at home, and conventional polysomnography was used to confirm the diagnosis. The apnea-hypopnea index (the total number of episodes of apnea and hypopnea divided by the number of hours of sleep) was calculated for each participant. RESULTS: The mean age of the participants was 44 years; 77 percent were men. As compared with those without sleep apnea, patients with an apnea-hypopnea index of 10 or higher had an odds ratio of 6.3 (95 percent confidence interval, 2.4 to 16.2) for having a traffic accident. This relation remained significant after adjustment for potential confounders, such as alcohol consumption, visual-refraction disorders, body-mass index, years of driving, age, history with respect to traffic accidents, use of medications causing drowsiness, and sleep schedule. Among subjects with an apnea-hypopnea index of 10 or more, the risk of an accident was higher among those who had consumed alcohol on the day of the accident than among those who had not. CONCLUSIONS: There is a strong association between sleep apnea, as measured by the apnea-hypopnea index, and the risk of traffic accidents. (+info)
Volume flow measurement in hemodialysis shunts using time-domain correlation.
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Volume flow was measured in 58 hemodialysis shunts (32 grafts and 26 radial fistulas) using the color velocity imaging-quantification method. This method is based on time-domain correlation for velocity calculation and integration of time-varying velocity profiles generated by M-mode sampling. Measurements were made in the brachial artery to estimate radial fistula flow or directly in the grafts. Intraoperator reproducibility was 14.9% for fistulas and 11.6% for grafts. Flow rate was significantly lower in abnormal shunts associated with a functional disorder or a morphologic complication (808 ml/min +/- 484) than in shunts associated with no abnormalities (1401 ml/min +/- 562). Receiver operating characteristic curves showed that a flow rate of 900 ml/min for fistulas and 1300 ml/min for grafts provided 81% and 79% sensitivity and 79% and 67% specificity, respectively. A functional disorder or a morphologic complication was associated with all fistulas and grafts in which flow rates were lower than 500 ml/min and 800 ml/min, respectively. (+info)
Signal-enhanced color Doppler sonography of deep venous thrombosis in the lower limbs and pelvis.
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Detection of Doppler signal tends to be more difficult in peripheral veins owing to low flow velocity. This can be caused by nonoccluding thrombosis, post-thrombotic wall changes, or a deep anatomic location of pelvic veins. The last-mentioned frequently is accompanied by interference by bowel gas. In addition, inappropriate insonation angles adversely affect the outcome of color-coded Doppler interrogation. The purpose of the present study was to evaluate the effectiveness of signal-enhanced color Doppler sonography on peripheral veins in 31 patients clinically suspected of having deep vein thrombosis. As a result of diagnostic uncertainty, additional enhanced studies were performed on 43 venous segments. The enhancement led to a decrease in false-positive results (from four patients to one patient) and false-negative results (from four patients to two patients) compared to unenhanced studies. Evaluation of the deeply located pelvic veins profited the most through signal enhanced Doppler sonography. (+info)