Biomedical subjects

M Nosal

Publications and source records attributed to M Nosal.

At least 19 recordsLinked to original sources

PubMed2006

New exposure-based metric approach for evaluating O(3) risk to North American aspen forests.

The United States and Canada currently use exposure-based metrics to protect vegetation from O(3). Using 5 years (1999-2003) of co-measured O(3), meteorology and growth response, we have developed exposure-based regression models that predict Populus tremuloides growth change within the North American ambient air quality context. The models comprised growing season fourth-highest daily maximum 8-h average O(3) concentration, growing degree days, and wind speed. They had high statistical significance, high goodness of fit, include 95% confidence intervals for tree growth change, and are simple to use. Averaged across a wide range of clonal sensitivity, historical 2001-2003 growth change over most of the 26 Mha P. tremuloides distribution was estimated to have ranged from no impact (0%) to strong negative impacts (-31%). With four aspen clones responding negatively (one responded positively) to O(3), the growing season fourth-highest daily maximum 8-h average O(3) concentration performed much better than growing season SUM06, AOT40 or maximum 1h average O(3) concentration metrics as a single indicator of aspen stem cross-sectional area growth.

Air Pollution↗

PubMed2003

A multi-variate statistical model integrating passive sampler and meteorology data to predict the frequency distributions of hourly ambient ozone (O3) concentrations.

A multi-variate, non-linear statistical model is described to simulate passive O3 sampler data to mimic the hourly frequency distributions of continuous measurements using climatologic O3 indicators and passive sampler measurements. The main meteorological parameters identified by the model were, air temperature, relative humidity, solar radiation and wind speed, although other parameters were also considered. Together, air temperature, relative humidity and passive sampler data by themselves could explain 62.5-67.5% (R(2)) of the corresponding variability of the continuously measured O3 data. The final correlation coefficients (r) between the predicted hourly O3 concentrations from the passive sampler data and the true, continuous measurements were 0.819-0.854, with an accuracy of 92-94% for the predictive capability. With the addition of soil moisture data, the model can lead to the first order approximation of atmospheric O3 flux and plant stomatal uptake. Additionally, if such data are coupled to multi-point plant response measurements, meaningful cause-effect relationships can be derived in the future.

Air Pollutants↗

PubMed2003

Improved patient survival following surgery for coarctation of the aorta.

BACKGROUND: We conducted a retrospective review of children undergoing surgery for coarctation of the aorta in our institution over the last ten years with the aim of evaluating overall patient survival as well as detecting factors affecting it. We tried to identify the risk factors for mortality. METHODS AND DATA: Between January 1992 and December 2001, 201 patients with aortic coarctation were operated on at the Department of Cardiac Surgery of the Children's University Hospital, Bratislava. The three classes of aortic coarctation were represented: isolated coarctation, coarctation with ventricular septal defect (VSD) and coarctation with complex cardiac anomalies. Patients' preoperative, operative and immediate postoperative medical records were carefully studied with special attention paid to the type of lesion, patients' preoperative state, type of surgical technique employed, as well as the period of operation. For comparison, two equal time periods of follow-up were reviewed--1992 to 1996 and 1997 to 2001. The overall postoperative conditions of patients were also regularly monitored. Patient data were statistically analyzed using the JMP program version 4.04. RESULTS: An overall survival of 90% was recorded over the period of follow-up, ranging between one and ten years. A further break down showed a statistically significant difference between the various types of aortic coarctation, p=0.0001. Patients with simple or isolated coarctation had a survival rate of 100%, those with ventricular septal defect (VSD) in addition to coarctation had a survival rate of 80% while patients with associated complex cardiac anomalies had a survival rate of 65%. An improvement on overall patient survival was recorded in the period between 1997 and 2001--96% as against 86% for the period between 1992 and 1996. On univariate statistical analysis, the following variables were identified as significant risk factors for death: 1) Complex cardiac anomalies (p<0.0001), 2) Age at operation less than one month (p<0.0001) and 3) Treatment prior to the year 1997 (p=0.02). CONCLUSION: A considerable improvement on patient survival following surgery for coarctation of the aorta was recorded over the last five years. This could be attributed to new measures in preoperative, operative and postoperative care for patients with aortic coarctation. (Tab. 4, Fig. 5, Ref. 8.).

Adolescent↗

PubMed2003

Recoarctation and patients' freedom from re-intervention--a study of patients undergoing surgery for coarctation of the aorta at the Department of Cardiac Surgery of the Children's University Hospital, Bratislava.

BACKGROUND: Many children and young adults have undergone surgery for coarctation of the aorta. Individual surgical techniques employed in the treatment of patients and their effects on incidence of recoarctation were reviewed. METHODS AND DATA: Over the last ten years, a total of 201 cases of aortic coarctation were surgically treated at our department. The three forms of coarctation of the aorta recognized by the Society for Cardiothoracic Surgeons namely: isolated coarctation, coarctation with ventricular septal defects and coarctation with complex cardiac anomalies, were represented. RESULTS: 19 cases of recoarctation were recorded over the period of follow-up, representing 10% of all operated patients. On univariate analysis, the risk of recoarctation was closely linked with the following variables: use of resection and end-to-end anastomosis (p=0.01), age at operation less than one month (p=0.0002) and weight at operation less than 3 kg (p=0.01). The risk of recoarctation was found to be highest when resection and end-to-end anastomosis was employed in neonates (p<0.0001). Most cases of recoarctation as shown by the Kaplan-Meier plot occurred within the first year after surgery. CONCLUSION: The use of simple resection and end-to-end anastomosis in neonates is associated with a high risk of recoarctation. Hence, our preferred surgical technique in neonates is the extended resection and end-to-end anastomosis, which is associated with a considerably lower risk of recoarctation in this age group. (Tab. 4, Fig. 5, Re. 7)

Aortic Coarctation↗

PubMed2003

Functional outcome of surgery for coarctation of the aorta.

AIM OF STUDY: Coarctation of the aorta (CoA) accounts for about 8% of all congenital heart diseases. This represents about 30 new cases of coarctation every year in Slovakia, of which more than half will require surgical treatment. Over the past years, many children with this diagnosis have been successfully operated on at the Department of Cardiac Surgery of the Children's University Hospital, Bratislava. Thus, the need for a comprehensive follow-up and analysis of the postoperative well being of these young patients arises. Our study is therefore aimed at: 1) identifying factors affecting the incidence and persistence of postoperative systemic hypertension, as well as the need for heart failure and hypertension treatment, 2) assessing patients' psychomotor development following surgery for coarctation of the aorta. METHODS AND DATA: Between January 1992 and December 2001, a total of 201 patients with aortic co-arctation were operated on at our institution. The three classes of aortic coarctation namely: isolated coarctation, coarctation with ventricular septal defect and coarctation with complex cardiac anomalies were represented. Patients' medical records were retrospectively reviewed, with attention paid to such variables as the type of lesion, gradient across the site of coarctation, type of surgical technique employed and surgery-related complications. Subsequently, these patients were followed for a time period ranging between six months and ten years during which their psychomotor development and overall clinical state were evaluated. RESULTS: Of the 201 operated patients, 64 (33%) had early postoperative hypertension, so-called paradoxical hypertension. There was a significant correlation between the incidence of early postoperative hypertension and patients' age at operation (p < 0.0001). Age at operation was also a significant risk factor for late hypertension (p = 0.005). In both cases we noticed a higher incidence of high blood pressure in patients operated on after the age of six years. The need for antihypertensive treatment of patients with early postoperative hypertension decreases with a younger age at operation. At five years of follow-up, the need for antihypertensive treatment was 15%. Clinical psychological evaluation of 64 patients showed a normal distribution of patients' intelligence quotients. No surgery-related variable correlated with the incidence of delayed mental development. There was, however, a certain correlation between the presence of complex anomalies and low verbal IQ in examined patients (p = 0.04) CONCLUSIONS: Early surgical treatment of aortic coarctation reduces the likelihood of early, as well as late postoperative hypertension. The preferred protocol in our institution is early surgical treatment of patients at about the age of two years. The need for antihypertensive treatment of patients at five years of follow-up is 15%. Patients' psychomotor development following surgery for aortic coarctation is not affected by type of surgical procedure. On the whole, we can conclude that patients' psychomo-whole, we can conclude that patients' psychomotor development does not differ from the rest of population. There is however, a certain correlation between complex cardiac anomalies and a tal, Bratislava delay in some components of patients' psychomotor development. (Tab. 3, Fig. 4, Ref. 17.)

Adolescent↗

PubMed2001

Relationships between passive sampler and continuous ozone (O3 ) measurement data in ecological effects research.

In ecological effects research, there is a rapid increase in the application of passive sampling techniques for measuring ambient ozone (O3) concentrations. Passive samplers provide data on cumulative exposures of a plant to a pollutant. However, O3 is not an accumulative contaminant within the plant tissue, and use of prolonged passive sampling durations cannot account for the dynamics of the occurrences of O3 that have a significant influence on the plant response. Therefore, a stochastic Weibull probability model was previously developed and applied to a site in Washington State (1650 m MSL) to simulate the cumulative exposure data from a passive sampler, to mimic the corresponding frequency distributions of hourly O3 concentrations that would otherwise have been obtained by continuous monitoring. At that site the correlation between the actual passive sampler and the continuous monitor data was R2 = 0.74. The simulation of the hourly O3 data was based on and compared with the results obtained from a colocated continuous monitor. In this paper we report the results of the model application to data from an unrelated monitoring site (New Hampshire, 476 m MSL) with poor correlation between the passive sampling and continuous monitoring (R2 = 0.24). In addition, as opposed to the previous work, we provide comparisons of the frequency distributions of the hourly O3 concentrations obtained by the simulation and the actual continuous monitoring. In spite of the major difference in the R2 values, at both sites the simulation provided very satisfactory results within the 95% confidence interval, suggesting its broad applicability. The final objective of this overall approach is to develop a generic model that can simulate reasonably well the occurrences of ambient O3 concentrations that are dependent upon the elevation of the measurement site and the synoptic and local meteorology. Such an effort would extend the relative utility of the passive sampling data in explaining stochastic plant responses.

Computer Simulation↗

PubMed2001

Use of passive ambient ozone (O3) samplers in vegetation effects assessment.

A stochastistic, Weibull probability model was developed and verified to simulate the underlying frequency distributions of hourly ozone (O3) concentrations (exposure dynamics) using the single, weekly mean values obtained from a passive (sodium nitrite absorbent) sampler. The simulation was based on the data derived from a co-located continuous monitor. Although at the moment the model output may be considered as being specific to the elevation and location of the study site, the results were extremely good. This effort for the approximation of the O3 exposure dynamics can be extended to other sites with similar data sets and in developing a generalized understanding of the stochastic O3 exposure-plant response relationships, conferring measurable benefits to the future use of passive O3 samplers, in the absence of continuous monitoring.

Air Pollutants↗

PubMed2000

Application of a stochastic, Weibull probability generator for replacing missing data on ambient concentrations of gaseous pollutants.

A stochastic, three-parameter, Weibull frequency distribution, probability generator was tested by using theoretical data. Subsequently, it was applied to replace missing values of hourly atmospheric concentrations of trace gases that were continuously monitored at three study sites, for 2 years. The results were highly accurate and realistic. The cumulative means and the medians calculated by the Weibull method were intermediate between corresponding values calculated by uniform substitution of missing values with 'zero' or with half of the minimum detection limit of the appropriate measurement instrument used. Furthermore, the Weibull method allowed the replacement of as many as 100 missing values on either side of a measured data sub-set, without altering the overall characteristics of the true frequency distribution of the entire data set.

Journal Article↗

PubMed1999

Surgical treatment of transposition of the great arteries.

BACKGROUND: With regard to risk of the failure of systemic right ventricle after physiological correction of transposition of great arteries, anatomic repair is a current method of choice. OBJECTIVE OF STUDY: Analysis of results of surgical correction of transposition of great arteries performed between 1992 and October 1998. METHOD: A total of 111 patients were operated on for transposition of the great arteries. In the 1st group of patients (n = 21, mean age was 135 +/- 55 days), physiological correction according to Senning was performed. Patients of the 2nd group (n = 90, mean age was 15.4 +/- 21.6 days) underwent anatomic repair. RESULTS: Early mortality was 6% (7 patients). Mean follow-up is 2.95 years (1.9 SD) ranging from 0.2 years to 6.1 years. Actuarial 1-month survival in the whole cohort (n = 111) is 94%, and it remains unchanged at 1, 2, 3, 4, 5, and 6 years of follow-up. Patients, who underwent surgery after 1997, show significantly better survival compared to those operated before 1997 (p = 0.0997). Thus, a date of operation (before 1997) is the only significant risk factor for death. Survival in patients operated after 1997 (n = 40) is 98%. All patients belonging to the 2nd group are in functional group NYHA 1. CONCLUSION: Anatomic repair of transposition of the great arteries is a method of choice for treatment of this congenital heart defect. Left ventricle becomes systemic ventricle, which is essential in view of long-term performance. Psychomotor development of children, who underwent ASO, is comparable with that of healthy population. (Tab. 3, Fig. 3, Ref. 18.)

Follow-Up Studies↗

PubMed1999

[Surgical treatment of total anomalous pulmonary venous return].

BACKGROUND: Total abnormal pulmonary venous return (TAPVR), mainly the obstructive type represents the most riskful critical congenital heart defect requiring urgent surgery immediately after birth. THE AIM OF THE STUDY: Analysis of surgical correction of TAPVR results performed from December 1992 to December 1998. METHODS: Twenty-seven patients underwent surgery for TAPVR. 13 of them (48%) presented with hemodynamically severe obstruction. Mean age in the group with obstruction was 3.6 +/- 3.2 days with mean weight of 3282 +/- 537 grams. RESULTS: From the 27 studied patients 5 (18.5%) died. Mean duration of the study in the whole group is 1.91 +/- 2.01 years. Actuarial survival in the first month is 85%, in the second month 81% and remains identical in the 1., 2., 3., 4., 5., 6. year of the study. Univariate analysis identified operation before the year 1996 (p = 0.0056) as a risk factor of immediate mortality. Introduction of ultrafiltration significantly eliminated mortality (p = 0.0101). Remaining variables (age, weight, sex, obstructive TAPVR, TAPVR, extracorporeal circulation duration, pulmonary hypertension) did not significantly influence the survival (p more than 0.05). Multivariate analysis defined operation before the year 1996 as the sole risk factor of mortality (p = 0.0033). In patients operated on in the year 1996 (n = 15) was the survival in the studied period 100%. CONCLUSION: Since the year 1996 the results of surgical treatment of TAPVR significantly improved. The key role in the improvement have better urgent diagnostic and surgery, improvement of surgical technique and myocardial protection, introduction of modified ultrafiltration and the quality of postoperative care. Psychomotor development of children after correction is comparable with healthy population, all patients are in NYHA I class. (Tab. 2, Fig. 4, Ref. 9.)

Heart Defects, Congenital↗

PubMed1998

A numerical analysis of the combined open-top chamber data from the USA and Europe on ambient ozone and negative crop responses.

Statistical analysis was performed using selected sets of combined data from the US National Crop Loss Assessment Network and the European Open-Top Chambers Programme to examine the relationships between the occurrences of hourly ambient ozone (O3) concentrations and adverse crop yield responses. The results suggest that the frequency of occurrences of relatively low hourly O3 concentrations ( approximately <35 ppb) are not as important as moderate to higher concentrations in eliciting negative crop biomass responses. They also suggest that daily peak (highest) hourly O3 values ( approximately >90 ppb) may not be as critical, most likely because they frequently do not occur during time periods when conditions that promote atmospheric conductivity (O3 deposition) and plant uptake (O3 absorption) are in coherence.

Journal Article↗

PubMed1995

Ambient ozone (O3) and adverse crop response: a unified view of cause and effect.

This paper presents a cohesive view of the dynamics of ambient O(3) exposure and adverse crop response relationships, coupling the properties of photochemical O(3) production, flux of O(3) from the atmosphere into crop canopies and the crop response per se. The results from two independent approaches ((a) statistical and (b) micrometeorological) were analyzed for understanding cause-effect relationships of the foliar injury responses of tobacco cv Bel-W3 to the exposure dynamics of ambient O(3) concentrations. Similarly, other results from two independent approaches were analyzed in: (1) establishing a micrometeorological relationship between hourly ambient O(3) concentrations and their vertical flux from the air into a natural grassland canopy; and (2) establishing a statistical relationship between hourly ambient O(3) concentrations in long-term, chronic exposures and crop yield reductions. Independent of the approach used, atmospheric conditions appeared to be most conducive and the crop response appeared to be best explained statistically by the cumulative frequency of hourly ambient O(3) concentrations between 50 ppb and 90 ppb (100 and 180 microg m(-3)). In general, this concentration range represents intermediate or moderately enhanced hourly O(3) values in a polluted environment. Further, the diurnal occurrence of this concentration range (often approximately between 0900 and 1600 h in a polluted, agricultural environment) coincided with the optimal CO(2) flux from the atmosphere into the crop canopy, thus high uptake. The frequency of occurrence of hourly O(3) concentrations > 90 ppb (180 microg m(-3)) appeared to be of little importance and such concentrations in general appeared to occur during atmospheric conditions which did not facilitate optimal vertical flux into the crop canopy, thus low uptake. Alternatively, when > 90 ppb (180 microg m(-3)) O(3) concentrations occurred during the 0900-1600 h window, their frequency of occurrence was low in comparison to the 50-90 ppb (100-180 microg m(-3)) range. Based on the overall results, we conclude that if the cumulative frequency of hourly ambient O(3) concentrations between 50-62 ppb (100-124 microg m(-3)) occurred during 53% of the growing season and the corresponding cumulative frequency of hourly O(3) concentrations between 50-74 ppb (100-148 microg m(-3)) occurred during 71% of the growing season, then yield reductions in sensitive crops could be expected, if other factors supporting growth, such as adequate soil moisture are not limiting.

Journal Article↗

PubMed1994

Ambient ozone and crop loss: establishing a cause-effect relationship.

This paper provides the results of a retrospective mathematical analysis of the US NCLAN (National Crop Loss Assessment Network) open-top chamber data. Some 77% of the 73 crop harvests examined, showed no statistically significant yield differences between NF (non-filtered open-top chamber) and AA (chamberless, ambient air) treatments (no easily discernable chamber effects on yield). However, among these cases only seven acceptable examples showed statistically significant yield reductions in NF compared to the CF (charcoal filtered open-top chamber) treatment. An examination of the combined or cumulative hourly ambient O3 frequency distribution for cases with yield loss in NF compared to a similar match of cases without yield loss showed that the mean, median and the various percentiles were all higher (>/= 3 X) in the former in contrast to the latter scenario. The combined frequency distribution of hourly O3 concentrations for the cases with yield loss in NF were clearly separated from the corresponding distribution with no yield loss, at O3 concentrations > 49 ppb. Univariate linear regressions between various O3 exposure parameters and per cent yield losses in NF showed that the cumulative frequency of occurrence of O3 concentrations between 50 and 87 ppb was the best predictor (adjusted R2 = 0.712 and p = 0.011). This analysis also showed that the frequency distribution of hourly concentrations up to 87 ppb O3 represented a critical point, since the addition of the frequency distributions of > 87 ppb O3 did not improve the R2 values. In fact as the frequency of hourly O3 concentrations included in the regression approached 50-100 ppb, the R2 value decreased substantially and the p value increased inversely. Further, univariate linear regressions between the frequencies of occurrence of various O3 concentrations between 50 and 90 ppb and: (a) cases with no yield difference in NF and (b) cases with yield increase in NF compared to the CF treatment (positive effect) provided no meaningful statistical relationship (adjusted R2 = 0.000) in either category. These results support the basis that additional evaluation of the frequency of occurrence of hourly O3] concentrations between 50 and 87 ppb for cases with the yield reductions could provide a meaningful ambient O3 standard, objective or guideline for vegetation.

Journal Article↗

PubMed1993

Use of tobacco cultivars as biological indicators of ambient ozone pollution: an analysis of exposure-response relationships.

A summary is presented of the numerical analysis of the results from a study of exposure in an open-top chamber conducted at two locations in the north-east USA, utilizing tobacco (Nicotiana tabacum L.) cv. Bel-W3 (sensitive) and cv. Bel-B (tolerant) as differential indicators of ambient O(3) pollution. At both study sites, Bel-W3 was significantly more sensitive than Bel-B. There were differences in the weekly O(3) exposure dynamics and the consequent foliar injury scores on Bel-W3 between the two study sites. During the individual weekly exposures, the bottommost fully expanded leaf (leaf no. 1) on Bel-W3 was more sensitive than the second fully expanded leaf (leaf no. 2). There were no statistically significant differences in the injury scores on Bel-W3 leaf no. 1 between the non-filtered air open-top chamber and the chamberless, ambient field plot treatments at both study sites. In Mallow's critical-point best regression, among the many O(3) descriptors tested, number of hours during each week with O(3) concentrations > 40 ppb (N40) and > 60 ppb (N60) or the corresponding sums of their concentrations (SUM40 and SUM60) proved to be the best predictors of foliar injury on Bel-W3, leaf no. 1. The regression used N40 and N60 or SUM40 and SUM60 together and did not identify each variable alone or by itself as being important. Independent of this, all the R(2) values could account for only about 30-32% of the variability of the foliar injury responses, although these values were statistically significant. Covariance time-series analysis between weekly O(3) concentrations > 40 ppb and the corresponding foliar injury scores on Bel-W3 leaf no. 1 showed that foliar injury was in best spectral coherence with the O(3) exposure (> 40 ppb) during periods of moderate periodicity (variance). The overall results suggest that the visible foliar responses of tobacco Bel-W3 can be used as a qualitative, but not necessarily as a quantitative indicator of relative ambient O(3) pollution on a generalized temporal or spatial scale.

Journal Article↗

PubMed1991

Ozone and the clean troposphere: ecological implications.

In recent years numerous investigations have examined the relationships between chronic ozone (O(3)) exposure and plant responses using statistical or empirical cause-effect models. One of the critically important decisions underlying these studies has been the choice of the control or reference O(3) exposure to which all other treatments are compared. The issue of the control or reference O(3) exposure is a complex one. Does a single ambient control or reference O(3) exposure exist? The approach taken in this paper is to examine the O(3) concentrations in the 'clean troposphere.' One must ask what a clean troposphere is and whether there are any geographic locations in the world today that are totally free of human influences. Data on photochemical oxidants from Fortress Mountain, Alberta, Canada, are examined. A comparison of these data with air quality data from other locations in North America is used to examine the design of vegetation response studies. The need for integrated research design, execution, and evaluation is stressed.

Journal Article↗

PubMed1989

Application of spectral coherence analysis to describe the relationships between ambient ozone exposure and crop growth.

Growth season-based time series spectral coherence analysis was performed between weekly changes in hourly ambient O(3) concentrations and weekly changes in alfalfa height growth. Weekly median hourly O(3) concentration and the corresponding weekly cumulative integral (sum of all hourly concentrations within the week) were used as indicators of weekly O(3) spectral density and coherence with the change in weekly alfalfa height growth. In general, the weekly cumulative integral performed much better than the weekly median O(3) concentration. A conceptual analysis of the results is presented, along with a recommendation that crop growth stage-based cumulative integrals merit further evaluation towards a better understanding of cause-effect relationships.

Journal Article↗

PubMed1989

A multivariate, time series model to relate alfalfa responses to chronic, ambient sulfur dioxide exposures.

A multivariate dual time series model is described here to relate chronic sulfur dioxide exposures to alfalfa responses under ambient conditions. The model considers the time series of SO(2) exposures and the growth dynamics of the crop in accounting for the final harvested biomass. The model also allows the inclusion of environmental variables such as temperature and precipitation. Coupled with the model, the 'best' regression method used facilitates the segregation or identification of the contribution of individual independent variables to the final coefficient of determination for the harvested biomass.

Journal Article↗

PubMed1989

The epidemiology of mumps in southern Alberta 1980-1982.

The full spectrum of mumps in Southern Alberta was studied over the years 1980-1982. In the community, a random sample of 3,497 children was tested for prevalence of immunity to mumps. The 1,816 who were not immune were retested after one year. The incidence of new immunity was 16.5%. Most seroconverters had no illness suggestive of mumps. History of previous mumps or immunization were found to be unreliable predictors of serologic immune status. In the family study, information was obtained on 342 cases diagnosed as mumps by family physician recorders. The overall complication rate was 10.8% and the secondary attack rate within families was 11.7%. Hospital records of all 25 patients admitted in Calgary with mumps during the same period were analyzed. Estimated costs of unopposed mumps over 20 years compared with the estimated costs of vaccination showed that a vaccination program could give a benefit-cost ratio between 6.4 and 247. These studies show that mumps is a mild disease with relatively few serious complications or sequelae. Even so, there would be definite medical and economic benefit with immunization. A low-cost addition of mumps vaccine to the immunization program would be justified.

Adolescent↗