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PubMed2004

Is patient readiness to change a predictor of improved glycemic control?

OBJECTIVE: To test the hypothesis that patient readiness to change (RTC) predicts future changes in glycemic control in adults with diabetes. RESEARCH DESIGN AND METHODS: We linked survey data with HbA1c data for a stratified random sample of consenting adults with diabetes. Change in HbA1c from baseline to the 1-year follow-up was computed and used as a dependent variable. Linear regression models assessed RTC and other patient variables as predictors of HbA1c change. RESULTS: Among 617 patients with baseline HbA1c > or = 7% and complete data for analysis, RTC predicted subsequent improvement in HbA1c for those with higher physical functioning (interaction t = -2.45, P < 0.05). Other factors that predicted HbA1c improvement in multivariate linear regression models included higher self-reported medication adherence (t = -4.41, P < 0.01), higher baseline HbA1c (t = -15.08, P < 0.01), and older age (t = -2.61, P < 0.01). CONCLUSIONS: Diabetes RTC independently predicts change in HbA1c for patients with high but not for patients with low functional health status. Customized use of RTC assessment may have potential to improve care.

Adult↗

PubMed1996

Study of the safe threshold of apneic period in children during anesthesia induction.

STUDY OBJECTIVES: (1) To investigate changes in arterial oxygen saturation via pulse oximeter (SpO2) during apnea and after reinstitution of manual ventilation at SpO2 of 95% or 90% following rapid sequence induction of anesthesia in children after 2-minute preoxygenation; (2) to determine whether the setting of a safe threshold of apneic period to an SpO2 of 95% is appropriate in children during anesthetic induction; and (3) to evaluate the influences of age, body weight, and height on the time from the start of apnea to SpO2 of 95%. DESIGN: A clinical study of random design and comparison among groups. SETTING: Operating room of a plastic surgery hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College. PATIENTS: 152 infants and children, ASA physical status 1, aged 3 months to 12 years, scheduled for elective plastic surgery. INTERVENTIONS: Patients were divided into three age groups: Group 1-infants 3 months to 1 year (n = 39); Group 2 children 1 to 3 years (n = 41); and Group 3-children 3 to 12 years (n = 72). Patients in each age group were randomly allocated again to Subgroups A and B. After a 2-minute preoxygenation, anesthesia was induced with thiopental 5 mg/kg, fentanyl 5 micrograms/kg and suxamethonium 1.5 mg/kg. Patients were manually ventilated when SpO2 decreased to 90% in Subgroups A and 95% in Subgroups B, respectively, during apnea. MEASUREMENTS AND MAIN RESULTS: SpO2 was measured continuously with a Datex pulse oximeter applied to the right index finger. During apnea, the times for SpO2 to decrease to 09% (T99) and 95% (T99) in all children, and 90% (T90) in Subgroups A were recorded. The time for SpO2 to decrease from 95% to 90% (T95-90) in Subgroups A was also measured. After reinstitution of manual ventilation, the time when SpO2 continued to decrease (T1) and the time from the end of apnea to recovery of SpO2 baseline (T2) were determined. In addition, the lowest value of SpO2 after apnea was also recorded. The results showed that younger children were more susceptible than older children to the risk of hypoxemia during apnea. There were significant differences in T99, T95, T90, and T95-90 between the three age groups T1 and T2 were significantly longer in Group 3 than in Groups 1 and 2. There were significant differences in the lowest values of SpO2 following apnea among the three Subgroups A and between Subgroups A and B of each age group. During apnea, heart rate decreased gradually as SpO2 decreased, showing a significant decrease at SpO2 of 95%. Bradycardia was found in three children in Subgroups A. The apnea time to SpO2 of 95% correlated well with age, weight, and height by linear regression analysis. CONCLUSIONS: The safe threshold of an apneic period setting to an SpO2 of 95% was appropriate in children during anesthesia induction. Despite the same duration of preoxygenation, younger children were more susceptible than elder ones to the risk of hypoxemia during apnea. The apnea time to SpO2 of 95% correlated with age, body weight, and height using linear regression analysis.

Age Factors↗

PubMed2006

In vivo plaque characterization using intravascular ultrasound-virtual histology in a porcine model of complex coronary lesions.

OBJECTIVE: To determine the accuracy of detection of different tissue types of intravascular ultrasound-virtual histology (IVUS-VH) in a porcine model of complex coronary lesions. METHODS AND RESULTS: Coronary lesions were induced by injecting liposomes containing human oxidized low-density lipoprotein into the adventitia of the arteries. IVUS-VH imaging was performed in vivo at 8.2+/-1.6 weeks after injection. A total of 60 vascular lesions were analyzed and compared with their correspondent IVUS-VH images. Correlation analysis was performed using linear regression models. Compared with histology, IVUS-VH correctly identified the presence of fibrous, fibro-fatty, and necrotic tissue in 58.33%, 38.33%, and 38.33% of lesions, respectively. The sensitivity of IVUS-VH for the detection of fibrous, fibro-fatty, and necrotic core tissue was 76.1%, 46%, and 41.1% respectively. A linear regression analysis performed for each individual plaque component did not show strong correlation that would allow significant prediction of individual values. CONCLUSIONS: In a porcine model of complex coronary lesions, IVUS-VH was not accurate in detecting the relative amount of specific plaque components within each individual corresponding histological specimen.

Animals↗

PubMed1996

Analysis of progressive change in automated visual fields in glaucoma.

PURPOSE: To detect and estimate the rate of progression of visual field loss in subjects with glaucoma who undergo long-term automated perimetric visual field testing. METHODS: Automated visual field data were obtained for subjects with glaucomatous visual field loss and a minimum of seven threshold field tests over at least 4.5 years. Univariate linear regression was performed with respect to mean deviation (MD), corrected pattern standard deviation (CPSD), mean thresholds of clusters corresponding to the Glaucoma Hemifield Test (GHT), and thresholds of 52 individual test locations. Subjects were classified as progressive or stable (unchanged or improved) based on the slope and statistical significance of these parameters. Adjusted P values were used to maintain the overall type 1 error at 5%. RESULTS: One hundred ninety-one subjects with a mean follow-up period of 7.1 years (range, 4.5 to 10.5 years) and a mean number of visual field tests of 9.5 (range, 7 to 16) were included. Twenty-four subjects (12.6%) showed progression in MD (mean slope [95% confidence interval], -1.26 [-1.50, -1.01] dB/year), and 27 (14.1%) showed progression in CPSD (mean slope [95% confidence interval], 0.71 [0.58, 0.84] dB/year). Thirty-five subjects (18.3%) had > or = 1 progressive GHT cluster. The mean slope in progressive clusters ranged from -1.51 [-1.82, -1.20] to -2.84 [-3.39, -2.29] dB/year. Thirty-six subjects (18.8%) had > or = 1 progressive individual test locations. Fifty-two subjects (27.2%) were classified as progressive based on progression of CPSD, > or = 1 cluster and/or > or = 1 point. CONCLUSIONS: Fewer than 1 in 3 subjects progressed by any one of the criteria for progression over an average of 7.1 years. Rates of progression that could be statistically confirmed were in the range of approximately 1 to 5 dB/year, depending on the number of fields, the variability over time, and the parameter assessed (global indices, GHT clusters, or individual points). No correlation between initial visual field status and the rate of progression was found. A minimum of approximately 5 years of follow-up with annual perimetry would be required to detect significant changes in the visual field by linear regression.

Adolescent↗

PubMed2002

Correlational study of central corneal thickness measurements on Hong Kong Chinese using optical coherence tomography, Orbscan and ultrasound pachymetry.

BACKGROUND: Central corneal thickness (CCT) of 74 eyes from 39 normal Hong Kong Chinese subjects with ages ranging from 39 to 86 years were studied. AIM & PURPOSE: To compare the measurements of different devices and to compare the results of ethnic groups in other studies. METHODS: Non-contact measurements by Orbscan and Optical Coherence Tomography (OCT) were first carried out, followed by contact measurement using Ultrasound Pachymetry. The results of five measurements of Ultrasound Pachymetry and three measurements of OCT and Orbscan were each averaged and compared using correlation, linear regression and one-way analysis of variance methods. RESULTS: The measurements of three devices were significantly correlated (P < 0.01). The mean CCT in our study group measured by Orbscan (with an acoustic factor set at 0.92), Ultrasound Pachymetry and OCT were 555.96 +/- 32.41, 555.11 +/- 35.30 and 523.2 +/- 33.54 microm respectively. A linear regression model (using ultrasound measurements as standard) was presented. CONCLUSIONS: When a correction factor of 32 microm was applied to OCT measurements, the means of three devices became significantly equal. The adjusted OCT measurements were less precise within subjects but more accurate than Orbscan when compared with ultrasound pachymetry as a reference standard. The mean CCT measurement of our sample was comparable to some studies on Hong Kong Chinese, Caucasians and Japanese but higher than those on some Europeans, Asian and North Americans of African origin.

Adult↗

PubMed2003

Calibrated oxygen permeability of 35 conventional hydrogel materials and correlation with water content.

PURPOSE: The relationship between oxygen permeability (Dk) and water content of conventional hydrogel materials was reviewed using upgraded methods to measure both parameters in a masked fashion. This is the first report of conventional hydrogel Dk values that were calibrated using a set of reference materials and determined in the general format of ANSI Z80.20:1998 and ISO 9913- 1:1996. METHODS: Calibrated, corrected polarographic Dk values were determined at 35 degrees C for 35 conventional hydrogel materials available as contact lenses, obtained commercially. The refractive index was measured with an Abbe-type refractometer at room temperature and converted to water content by gravimetric adjustment of a volumetric equation derived from the Gladstone-Dale relationship. RESULTS: Percentages of the water content of the materials determined by gravimetric adjustment (GAWC%) ranged from 33.8% to 70.7% and were strongly correlated with the gravimetric water contents stated by their manufacturers (SWC%). The linear regression was GAWC% = 1.004(SWC%)-2.403, with coefficient of determination (R2) = 0.929. R2 values of the corrected oxygen resistance (t/Dk) versus thickness (t) plots for the 35 materials were 0.96 or greater. Calibrated, corrected Dk values ranged from 8.4 to 44.8 Dk units and were strongly correlated with water content in a semilogarithmic manner. The linear regression was Log(Dk) = 0.01754 (GAWC%) + 0.3897, with R2 = 0.945 over the ranges of water content and Dk noted above. CONCLUSIONS: Water content determined by gravimetric adjustment of the known volumetric relationship was slightly more than 2% less, on average, than that stated by contact lens manufacturers. This was likely the result of the greater tonicity of the storage solution in this study or more pronounced blotting prior to measurement, or both; yet the soft lenses and blotting method were the same as used for Dk assessment. Commercially available soft lenses were consistently manufactured, the blotting method was sufficient, and the polarographic Dk methodology was reliable such that linear resistance (t/Dk) versus thickness (t) plots resulted from lenses of different lots made of material having the same name. The semilogarithmic relationship of Dk and water content survived correction for boundary layers, correction for the edge effect, and calibration. Logically, the next step would be to refine this relationship even further by determining water content at the same temperature as oxygen permeability, 35 degrees C.

Contact Lenses, Hydrophilic↗

PubMed2001

Quality of life and psychological adaptation after surgical treatment for localized renal cell carcinoma: impact of the amount of remaining renal tissue.

OBJECTIVES: To analyze the quality of life and psychological adjustment after surgical therapy for localized renal cell carcinoma. METHODS: Postal questionnaires including measures of quality of life (SF-36) and the impact of the stress of cancer (Impact of Events Scale) were completed by 97 patients who had undergone radical or partial nephrectomy for localized renal cell carcinoma. Data were analyzed for the group as a whole and comparing the partial nephrectomy and radical nephrectomy groups. The variables examined included the impact of the type of partial nephrectomy (elective versus mandatory) and the amount of self-reported renal tissue remaining. RESULTS: The quality of life for the group as a whole was good, with no significant differences between the sample and U.S. norms for an age and sex-matched community sample on both the mental and physical health composite scores. Having undergone a partial versus a radical nephrectomy did not influence the patients' overall quality of life. Multiple linear regression modeling demonstrated that having more remaining renal parenchyma was an independent predictor of better self-reported physical health on the SF-36 (P <0.001). The entire sample had low mean scores on both avoidance and intrusion on the Impact of Events Scale, suggesting a lack of daily anxiety about cancer. Multiple linear regression modeling showed that patients who reported having more remaining renal parenchyma had lower intrusion and avoidance scores (P = 0.002 and 0.01, respectively). Multiple logistic regression modeling also demonstrated that the patients' perception of their remaining renal parenchyma was associated with less concern about cancer recurrence (P = 0.018) and less impact of cancer on patients' overall health (P <0.001). CONCLUSIONS: Most survivors of localized kidney cancer have normal physical and mental health regardless of the type of nephrectomy performed. The quality of life is better for patients with more renal parenchyma remaining after surgery for localized renal cell carcinoma.

Adaptation, Psychological↗

PubMed2006

Different regression equations relate age to the incidence of Lauren types 1 and 2 stomach cancer in the SEER database: these equations are unaffected by sex or race.

BACKGROUND: Although impacts upon gastric cancer incidence of race, age, sex, and Lauren type have been individually explored, neither their importance when evaluated together nor the presence or absence of interactions among them have not been fully described. METHODS: This study, derived from SEER (Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute) data, analyzed the incidences of gastric cancer between the years 1992-2001. There were 7882 patients who had developed gastric cancer. The total denominator population was 145,155, 669 persons (68,395,787 for 1992-1996, 78,759,882 for 1997-2001). Patients with multiple tumors were evaluated as per the default of the SEER*Stat program. 160 age-, five year period (1992-1996 vs 1997-2001)-, sex-, race (Asian vs non-Asian)-, Lauren type- specific incidences were derived to form the stratified sample evaluated by linear regression. (160 groups = 2 five year periods x 2 race groups x 2 sexes x 2 Lauren types x 10 age groups.) Linear regression was used to analyze the importance of each of these explanatory variables and to see if there were interactions among the explanatory variables. RESULTS: Race, sex, age group, and Lauren type were found to be important explanatory variables, as were interactions between Lauren type and each of the other important explanatory variables. In the final model, the contribution of each explanatory variable was highly statistically significant (t > 5, d.f. 151, P < 0.00001). The regression equation for Lauren type 1 had different coefficients for the explanatory variables Race, Sex, and Age, than did the regression equation for Lauren type 2. CONCLUSION: The change of the incidence of stomach cancer with respect to age for Lauren type 1 stomach cancer differs from that for Lauren type 2 stomach cancers. The relationships between age and Lauren type do not differ across gender or race. The results support the notion that Lauren type 1 and Lauren type 2 gastric cancers have different etiologies and different patterns of progression from pre-cancer to cancer. The results should be validated by evaluation of other databases.

Adult↗

PubMed2003

T2 relaxation time analysis in patients with multiple sclerosis: correlation with magnetization transfer ratio.

The aim of the current study was to perform T2 relaxation time measurements in multiple sclerosis (MS) patients and correlate them with magnetization transfer ratio (MTR) measurements, in order to investigate in more detail the various histopathological changes that occur in lesions and normal-appearing white matter (NAWM). A total number of 291 measurements of MTR and T2 relaxation times were performed in 13 MS patients and 10 age-matched healthy volunteers. Measurements concerned MS plaques (105), NAWM (80), and "dirty" white matter (DWM; 30), evenly divided between the MS patients, and normal white matter (NWM; 76) in the healthy volunteers. Biexponential T2 relaxation-time analysis was performed, and also possible linearity between MTR and mean T2 relaxation times was evaluated using linear regression analysis in all subgroups. Biexponential relaxation was more pronounced in "black-hole" lesions (16.6%) and homogeneous enhancing plaques (10%), whereas DWM, NAWM, and mildly hypointense lesions presented biexponential behavior with a lower frequency(6.6, 5, and 3.1%, respectively). Non-enhancing isointense lesions and normal white matter did not reveal any biexponential behavior. Linear regression analysis between monoexponential T2 relaxation time and MTR measurements demonstrated excellent correlation for DWM( r=-0.78, p<0.0001), very good correlation for black-hole lesions( r=-0.71, p=0.002), good correlation for isointense lesions( r=-0.60, p=0.005), moderate correlation for mildly hypointense lesions( r=-0.34, p=0.007), and non-significant correlation for homogeneous enhancing plaques, NAWM, and NWM. Biexponential T2 relaxation-time behavior is seen in only very few lesions (mainly on plaques with high degree of demyelination and axonal loss). A strong correlation between MTR and monoexponential T2 values was found in regions where either inflammation or demyelination predominates; however, when both pathological conditions coexist, this linear relationship is lost.

Adolescent↗

PubMed1991

Comparison of three methods for measuring respiratory mechanics in ventilated children.

Continuous measurements of airway pressure, gas flow, and tidal volume were made in 22 mechanically ventilated children, both during steady state conditions and following airway occlusion at end-inflation. For each child, three methods of analyzing the stored data were used to generate values of respiratory system compliance and resistance: 1) end-inspiratory hold technique (Bone: Respir Care 28:597, 1983; Rossi et al. Am Rev Respir Dis 131:672, 1985); 2) constant flow technique (Rossi et al. J Appl Physiol 58:1849, 1985; Suratt et al. J Appl Physiol 49:1116, 1980); and 3) multiple linear regression (Roy et al. Comput Biomed Res 7:21, 1974; Bhutani et al. Pediatr Pulmonol 4:150, 1988). In the absence of an accepted standard, we used the inspiratory hold technique as a reference. All methods gave comparable values for respiratory mechanics over a wide clinical range. However, multiple linear regression was the most convenient of the three: it can be automated and continuously displayed, there is no subjective input, values are taken through the respiratory cycle, and it is completely noninvasive. We also found that respiratory system resistance was largely a measure of endotracheal tube resistance and that respiratory compliance is a more sensitive monitor of lung function in intubated children.

Airway Resistance↗

PubMed2002

Different time evolution of oxyhemoglobin and deoxyhemoglobin concentration changes in the visual and motor cortices during functional stimulation: a near-infrared spectroscopy study.

Neurovascular coupling is the generic term for changes in cerebral metabolic rate of oxygen (CMRO(2)), cerebral blood flow, and cerebral blood volume related to brain activity. The goal of this paper is to better understand the effects of neurovascular coupling in the visual and motor cortices using frequency-domain near-infrared spectroscopy. Maps of concentration changes in oxyhemoglobin [O(2)Hb], deoxyhemoglobin [HHb], and total hemoglobin of the visual and motor cortices were generated during stimulation using a reversing checkerboard screen and palm-squeezing, respectively. Seven healthy volunteers of 18-37 years of age were included. In the visual cortex the patterns of [O(2)Hb] and [HHb] were strongly linearly correlated (r(2) > 0.8 in 13 of a total of 24 locations). In 20 locations the change in [O(2)Hb] was larger than 0.25 microM. The mean slope of the linear regression between [O(2)Hb] and [HHb] was -3.93 +/- 0.31 (SE). The patterns of the [O(2)Hb] and [HHb] traces over the motor cortex looked different. The [O(2)Hb] reached its maximum change a few seconds before the [HHb] reached its minimum. This was confirmed by the linear regression analysis (r(2) > 0.8 in none of 40 locations). In 20 locations the change in [O(2)Hb] was larger than 0.25 microM. The mean slope of the regression line was -1.76 +/- 0.20, which is significantly higher than that in the motor cortex (P < 0.0000001). Patterns of [O(2)Hb] and [HHb] differ among cortex areas. This implies that the regulation of perfusion in the visual cortex is different from that in the motor cortex. There is evidence that the CMRO(2) increases substantially in the visual cortex, while this is not the case for the motor cortex.

Blood-Brain Barrier↗

PubMed2005

Factors affecting collaborative care between pharmacists and physicians.

BACKGROUND: To have a positive impact on patient outcomes achieved with drug therapy, it is likely that pharmacists will work more closely with physicians to manage medications collaboratively. Yet, little is known about the factors that will support such collaborative care between pharmacists and physicians. OBJECTIVE: The objective of this study was to identify significant influences on collaborative care between pharmacists and physicians, from the perspective of pharmacists. METHODS: Data were collected through a survey mailed to a national sample of 321 pharmacists identified by state pharmacy associations as being innovative practitioners. Three types of influences were assessed: individual characteristics, contextual factors, and exchange characteristics. Individual characteristics included demographics and a personality measure. Context variables included practice environment and professional interactions between pharmacists and physicians. Exchange characteristics were trustworthiness, role specification, and relationship initiation. Four items asked about the pharmacist's collaborative care with a physician. A hierarchical linear regression analysis was performed with collaborative care as the dependent variable and the individual, context, and exchange characteristics as the independent variables. RESULTS: One hundred sixty-six usable surveys (53.4%) were returned. About 64% of the respondents were male, with a mean age of 43.7 (SD+/-11.2) years. Linear regression analysis of the complete model produced an R(2)=0.805 (P<.001). Significant predictors in the model included the context variable, professional interaction, and the exchange characteristics, trustworthiness and role specification. CONCLUSION: Overall, the collaborative working relationship model largely explained collaborative care between pharmacists and physicians. Researchers are encouraged to use these findings when studying pharmacist-physician collaboration. In addition, pharmacists seeking to work with physicians should attend to developing trustworthiness and clarifying their clinical roles with physicians.

Adult↗

PubMed2000

The use of 'electronic nose' sensor responses to predict the inhibition activity of alcohols on the cytochrome P-450 catalyzed p-hydroxylation of aniline.

A quantitative structure activity relationship (QSAR) has been formulated to describe the inhibitory action of a series of alcohols on the cytochrome P-450 catalyzed p-hydroxylation of aniline. The descriptors used in the QSAR are the responses of individual sensors in a polymer-based electronic nose, and are all easily generated experimental values. If the various electronic nose sensor response patterns for the family of test alcohols reflect differences in the chemical properties that are involved in the cytochrome P-450 inhibition process, it ought to be possible to correlate the differences in the electronic nose signals of these analytes with the differences in the cytochrome P-450 inhibition by these species. To evaluate this possibility, multiple linear regression was performed on data obtained from exposure of a series of test alcohols to 19 sensors of a conducting polymer composite electronic nose array. A genetic algorithm was then used to select the optimal set of sensors that best described the inhibitory activity of these alcohols within a linear regression model. The regression equation fit the inhibition data of 20 of the alcohols with an R of 0.995. This fit compares favorably with previously published QSARs on this system that have used log P (P triple bond octanol-water partition coefficient) along with steric parameters of the alcohols, and also compares favorably to QSARs formulated using theoretically calculated parameters.

Aniline Compounds↗

PubMed2004

Determining optimal nursing intensity: the RAFAELA method.

BACKGROUND: RAFAELA is a modern system of patient classification. In the last few years the system has become widely used in Finland and has aroused international interest. It comprises three parts: (1) The Oulu Patient Classification (OPC) instrument and (2) a file on nurse resources. Using these, the daily nursing care intensity, expressed as OPC points per nurse, can be calculated. The existing nursing care intensity can then be compared with the optimal by using the third instrument, (3) the Professional Assessment of Optimal Nursing Care Intensity Level (PAONCIL). This is a daily questionnaire that nurses complete in a 2-month period at intervals every few years. The daily workload is scored from -3 to +3, where zero is the optimal level. The optimal nursing care intensity per nurse is then defined by using linear regression analysis. No expensive time studies are needed. AIMS: This paper reports on a study which aimed to identify the minimum requirements for determining optimal nursing care intensity that allow the results to be accepted as correct, in terms of: length of the PAONCIL examination period, PAONCIL questionnaire response rate, explanatory power of the regression analysis and mean values of the OPC and PAONCIL instruments. DESIGN: The results of analyses of optimal nursing care intensity from 61 wards in eight Finnish hospitals for the period 1997-2001 are presented. The data do not contain any information about the identity of the patients. METHODS: Linear regression analysis, one-way analysis of variance, t-tests and correlation analysis were used, as well as parameters of distribution of the data. RESULTS: The results of the analysis of optimal nursing care intensity can be regarded as reliable if the PAONCIL response rate is above 70%, the period of examination is at least 3-4 weeks, the mean PAONCIL value is below 0.65 and the explanatory power is above 25%. CONCLUSION: On the basis of the RAFAELA system, the optimal nursing care intensity of a ward can be reliably determined. The prerequisites for achieving reliable results were clear and mostly fulfilled. Because a study period shorter than that which has previously been the practice is enough, the use of this system will be easier than before. The credibility and usefulness of the RAFAELA system have thus received considerable additional confirmation.

Analysis of Variance↗

PubMed1994

Conductance catheter measurements of left ventricular volume in the intact dog: parallel conductance is independent of left ventricular size.

OBJECTIVE: It has recently been suggested that conductance catheter parallel conductance (alpha Vc) is a function of left ventricular volume. To confirm this, alpha Vc was measured in this study over a wide range of steady state volumes. In addition, conductance derived volumes were compared to those obtained by radionuclide angiography to determine if the conductance catheter can be used to measure absolute left ventricular volume accurately in the intact dog heart. METHODS: Seven dogs were anaesthetised and instrumented with left ventricular conductance and pressure tip catheters, a flow through rho cuvette to continually measure blood resistance, a thermodilution catheter, and a venous catheter for volume infusion/withdrawal. Conductance and angiographic data were acquired at 8(SD 1) variably loaded states. Parallel conductance was measured twice at each state using a saline dilution technique and a new non-linear algorithm that allows variability in the observations of both maximum and minimum conductance volumes. RESULTS: The mean value of alpha Vc was 89.1(18.0) ml (71.8 to 111.3 ml) with a mean within-animal coefficient of variation of 7.3(3.4)%. Multiple linear regression using dummy variables to account for the large interanimal variability did not reveal any relationship between alpha Vc and either maximum or minimum left ventricular volume. Furthermore, no difference was found when alpha Vc values measured at the lowest and highest loading levels in each dog were compared. Linear regression showed good agreement between conductance and radionuclide derived end diastolic volumes (slope = 0.94, R = 0.9, p < 0.001). CONCLUSIONS: While alpha Vc varies between animals, it remains constant within any given animal over a broad range of left ventricular volumes. Thus the conductance catheter can provide reliable absolute left ventricular volume measurements under steady state conditions.

Animals↗

PubMed1995

Work related distal airway obstruction in an agricultural population.

OBJECTIVE: To assess the prevalence of distal airway obstruction and its risk factors in agricultural areas. METHODS: A cross sectional study of respiratory symptoms and lung function was performed among French farmers and their spouses (1122 subjects) who came for preventive medicine examinations. They answered a respiratory questionnaire and performed pulmonary function tests on a portable spirometer. Diagnoses of chronic bronchitis were made on the basis of reported chronic respiratory symptoms. Airway obstruction was determined from predicted values. Odds ratio (OR) and linear regression coefficients were calculated after stratification by smoking and history of cardiac and other respiratory diseases. RESULTS: Of respiratory symptoms prevalence of chronic cough was 8.47%, and chronic bronchitis 7.66%. Prevalence of distal airway obstruction was 11.4%, and overall airflow obstruction 3.2%. Smokers were 20.2% men, and 5.7% women. Linear regressions showed high association between pack-years in smokers or exsmokers and forced expiratory volume in one second/forced vital capacity (FEV1/VC) and forced expiratory flow between 25% and 75% of vital capacity (FEF25-75). In non-smokers without any history of cardiac or respiratory diseases, age and the size of farms had the highest correlations with these variables. OR for distal airway obstruction was 2.1 in subjects > 50 years old v the younger ones and 3.02 in the smaller farms v the larger ones. CONCLUSION: After stratification by smoking and history of cardiac and respiratory diseases, distal airway obstruction is present in agricultural areas. The age, and the size of farm are the highest respiratory risk factors in non-smokers.

Adolescent↗

PubMed2005

White matter anisotropy in childhood medulloblastoma survivors: association with neurotoxicity risk factors.

PURPOSE: To prospectively evaluate the relationships between change in white matter (WM) anisotropy and (a) patient age at craniospinal irradiation (CSI), (b) CSI dose, and (c) time of magnetic resonance (MR) imaging since CSI and to determine the effect of these neurotoxicity risk factors on WM anisotropy in posttreatment medulloblastoma survivors. MATERIALS AND METHODS: Informed consent was obtained from the patients, control subjects, or their parents, and the study was approved by the institutional review board. Twenty consecutive medulloblastoma survivors (14 male, six female; mean age, 11.0 years +/- 4.6 [standard deviation]) and 36 control subjects (14 male, 22 female; mean age, 10.7 years +/- 3.5) were examined. Control subjects were divided into four groups according to age: 5.0-7.9 years, 8.0-10.9 years, 11.0-13.9 years, and 14.0-18.9 years. The authors calculated the histogram-derived mean WM fractional anisotropy (FA) value for each patient and compared it with the mean WM FA value for the control subjects in the corresponding age group to evaluate the percentage change in WM FA (DeltaFA) in each patient. Spearman rank correlation analysis was used to analyze the relationships between DeltaFA and (a) age at CSI, (b) CSI dose, and (c) time of MR imaging since CSI. Then, multiple linear regression analysis was performed to study the simultaneous influence of these factors on DeltaFA. RESULTS: There were significant correlations between DeltaFA and both age at CSI (r = 0.631, P = .003) and CSI dose (r = -0.586, P = .007) but not between DeltaFA and time of MR imaging since CSI. Multiple linear regression analysis revealed age at CSI to be the only independent variable that significantly affected DeltaFA (adjusted r2= 0.391, P = .012). CONCLUSION: Loss of WM anisotropy is significantly affected by age at CSI, and there is a trend toward increasing anisotropy loss with larger CSI dose. Both age at CSI and CSI dose are known risk factors of neurotoxicity.

Adolescent↗

PubMed1997

Pressure-interval relationship characterizes left ventricular irregular beat contractilities and their mean level during atrial fibrillation.

How left ventricular (LV) contractility relates to irregular RR intervals during atrial fibrillation (AF) is still unclear. We investigated the relationship between the LV contractility (Emax) of individual beats and their preceding RR intervals during AF in isovolumic contractions is excised cross-circulated canine hearts, and additionally in ejecting contractions in in situ canine hearts. Atrial high-frequency electrical stimulation induced AF. We recorded a LV electrocardiogram, volume and pressure, and calculated the Emax of every arrhythmic beat. Multiple linear regression analysis between Emax and the six preceding RR intervals of all arrhythmic beats during 1 min AF showed the preceding RR interval (RR1) and the pre-preceding interval (RR2) to be the predominant predictors of Emax. The Emax-RR1/RR2 scattergram was closely fitted by a linear regression line. We found Emax at RR1/RR2 = 1 on the regression line to be virtually identical with both mean Emax during AF and stable Emax obtained during irregular atrial pacing at the same intervals as the mean RR interval during AF. These results newly indicate that the pressure-interval relationship predominantly characterizes LV irregular beat contractilities and their mean level during AF.

Animals↗