Variability of the closing volume measurement in normal subjects.

The repeatablilty of the measurement of closing volume (nitrogen method) in healthy, normal subjects was investigated. At least 7 consecutive measurements at 5-min intervals were made in each of 22 subjects. The mean coefficient of variation for the absolute volume of phase IV was 36.1 per cent and for the percentage ratio of phase IV to vital capacity, 36.1 per cent. Repeated measurements by the same observer of the same records on various days did not differ significantly (P greater than 0.5). There was a significant difference (P less than 0.05) between 2 observers measuring the same records, but there was no significant difference between the two observers in the variance of the closing variability in the same subject, it may be necessary to perform several closing volume maneuvers in each subject to establish his or her range before changes in the closing volume can be interpreted.     

Factors influencing breath condensate volume

Analysis of breath condensate (BC) has received interest recently due to the need for easy and repetitive monitoring or airway and pulmonary disease. While many authors have used custom built systems, commercial systems are now available and will probably be used more widely. Early studies of markers and mediators in BC have reported concentrations following varying periods of sampling time. However, factors that influence the generation of BC have not been analysed and it is unclear whether breathing rate, tidal volume, lung function, body weight, height or age influence the amount of BC collected. We therefore studied the influence of these factors on breath condensate volume and breath condensate urea and protein concentrations in 22 healthy volunteers and 23 COPD patients. A strong correlation of total respired volume and breath condensate volume was observed for both groups (volunteers: r=0.952, p < 0.0001, COPD: r=0.883, p < 0.001) while no significant correlation existed for breath condensate volume and TLC, RV, Vc, FEV1, R(tot), height or body weight, As long as ventilation remained fairly constant, breath condensate volume increased linearly with time. The fraction of breath condensate extracted from total vapour contained in the exhalate was estimated by measuring relative atmospheric humidity before and after the collecting tube. The amount calculated by the change in temperature and saturation corresponded closely to the amount actually collected. We conclude from these results that breath condensate volume is primarily dependent on V(E), and does not seem to depend on lung function parameters. For standardisation it is suggested to report breath condensate measurements per volume respired. Both, urea and protein are present in measurable quantities in breath condensate and protein as well as BCV may be helpful denominators for comparison with e.g. cytokines in lung disease.     

Appraisal of a new test: Between-technician variation in the measurement of closing volume.

To determine the between-technician variation in the measurement of closing volume, 24 subjects were divided into 3 blocks of 8 subjects each. Each block was then tested by a pair of technicians. Each of the 3 technicians involved in the study tested 16 subjects. It was later necessary to reject the tracings of 2 subjects in one of the 3 blocks, leaving 22 for analysis. The N2 method of determining closing volume was used. The statistical analysis was performed separately on the following measures derived from the tracings: expired vital capacity, planimetry of the area under the curve, total lung capacity, closing volume as a per cent of expired vital capacity, and closing capacity as a per cent of total lung capacity. All tracings were assessed by each technician. Two separate analyses of variance were then carried out to determine, respectively, the components of variance in the administration of the test and in the interpretation of the tracings. Because different persons were able to administer the test the same way, it seems that closing volume poses no problem in administration, provided that instructions as to how to perform the test are closely followed. In the interpretation of the tracings, significant differences were found for all measures, except planimetry; however, not all of these have the same practical implications. Some tracings were found "difficult" to interpret and contributed more to the over-all variation than did others. When making use of a new test in a population study, the between-technician variation should be determined before the study is begun.     

Factors influencing accuracy in left ventricular volume determination

The accuracy with which left ventricular volume is determined from contrast ventriculograms depends on the care with which the analysis protocol is followed. Therefore, the effect of variations in the method used for calculating the correction factor (CF) that adjusts for magnification and image distortion on volume calculation was measured. The results showed that error in the CF is caused by (in order of decreasing importance): filming the calibration figure at a different magnification mode from that of the ventriculogram, at a different height from the table than the level of the ventricle, or with the image intensifier at a different height than used during ventriculography; use of a calibration figure less than half the size of the ventricle; calculation of the CF from only 1 band pair of a banded catheter; or placement of the calibration figure at the periphery rather than the center of the imaging field. Error in volume determination was proportional to error in the CF. With care, the error in volume can be reduced to that due to interobserver variability in tracing the endocardial contours.     

A simplified method for measuring helium closing volume.

A simple method for delivering a constant volume of helium for the measurement of airway closing volume is described. Using a standard fiveway valve and PVC plastic irrigation pipe, a device was constructed which permits the delivery of a uniform volume of helium and avoids the troublesome valve change during inspiration. Results obtained when using this device were comparable to those with the use of conventional bag to contain the helium.     

Factors influencing ribavirin-induced hemolysis.

BACKGROUND/AIMS: One of the major side effects of the combination therapy for chronic hepatitis C is ribavirin-induced hemolytic anemia. Little is known about variables influencing this anemia. Our study tried to search for these variables in a large group of patients with hepatitis C treated with the combination therapy. METHODS: Two hundred and forty-four patients chronically infected with the hepatitis C virus were treated either with induction treatment (daily dose of interferon) or with a standard treatment (interferon thrice weekly). Both groups received 1,000-1,200 mg of ribavirin from week 4 until the end of the treatment. The drop in hemoglobin level was defined as the difference between the pretreatment hemoglobin level and the hemoglobin level at week 8. Seventeen variables which could possibly influence this drop in hemoglobin level were examined. RESULTS: After multivariate analysis, the drop in hemoglobin level was only significant influenced by pretreatment platelet level, treatment and haptoglobin phenotype. The ribavirin dose did not influence the drop in hemoglobin level or the early virological response. CONCLUSIONS: Ribavirin-induced hemolysis is influenced by the pretreatment platelet level, the administered amount of alpha-interferon and the haptoglobin phenotype. A careful search for the minimal dose of ribavirin needed in combination treatment is necessary.     

Intraindividual variability in maximal expiratory flow-volume and closing volume in asymptomatic subjects.

The variability of the parameters derived from analysis of the forced vital capacity and the expired nitrogen trace after a vital capacity inhalation of oxygen (closing volume) within a day, from day to day, and from week to week, has been determined. Effort-dependent tests as vital capacity and peak expiratory flow showed the least variability. The greatest variability was seen in effort-independent tests of function such as the maximal expiratory flow rate at 25 per cent (75 per cent of expired vital capacity) and 50 per cent of vital capacity, as well as closing volume. The degree of variability in the tests used was uninfluenced by the periodicity of the tests or the age or smoking habits of the subjects tested. It is suggested that variability of tests of respiratory function should be taken into account in their interpretation.     

Factors influencing the successful treatment of infectious pulmonary tuberculosis.

SETTING: Achieving successful treatment of infectious pulmonary tuberculosis (PTB) could reduce the spread of tuberculosis (TB) and the emergence of multidrug resistance. OBJECTIVE: To explore factors associated with successful treatment for sputum-positive PTB. DESIGN: This study used a population-based retrospective cohort design. All PTB patients residing in southern Taiwan recorded in the tuberculosis registry from 1 January to 30 June 2003 were identified. Each patient's medical record was requested from treating hospitals and retrospectively reviewed for 15 months after the date PTB was confirmed. RESULTS: There were 399 PTB patients included in the study. Factors significantly associated with successful treatment included treatment by pulmonologists (OR 1.93), receiving directly observed therapy (DOT) (OR 1.76) and receiving treatment at the chest hospital (OR 5.41). Patients of advanced age were less likely to achieve treatment success (OR 0.97). Among patients treated by pulmonologists, those treated at the chest hospital had a significantly higher treatment success rate than those treated at other institutions (94.1% vs. 69.9%). CONCLUSIONS: Patients treated with DOT and by pulmonologists, especially at the chest hospital, had a higher treatment success rate. DOT and training of care professionals and institutions are therefore important factors that affect the successful treatment of TB.     

Factors influencing the development of hypercholesterolemia after cardiac transplantation.

Although hypercholesterolemia is a frequent complication in cardiac transplant recipients, the exact mechanisms contributing to its development are not known. Cholesterol levels in 151 thoracic transplant patients treated with cyclosporine, azathioprine and prednisone were retrospectively examined to evaluate the factors influencing the heterogeneity of changes after the first year after transplantation in patients on a standard 3-drug immunosuppression regimen. Three groups were compared including ischemic heart transplant (n = 72), nonischemic heart transplant (n = 64) and heart-lung/lung transplant (n = 15) recipients. After the first year, 64 patients (43%) developed consistent hypercholesterolemia (greater than 240 mg/dl) for which pharmacologic treatment was initiated. Forty-eight patients (67%) in the ischemic heart transplant group required treatment, significantly (p less than 0.001) greater than both the nonischemic (n = 14; 22%) and heart-lung/lung transplant (n = 2; 13%) group. Univariate and forward stepwise multivariate regression analysis identified 4 factors that were all significantly and independently correlated with follow-up cholesterol including prednisone dose (p less than 0.001), baseline cholesterol (p less than 0.001), glucose (p less than 0.001) and weight gain (p less than 0.01). Changes in triglycerides in the 3 groups of patients were similar to changes in cholesterol. Furthermore, the increase in cholesterol in patients requiring treatment was primarily due to an increase in low-density lipoprotein cholesterol. These data demonstrate that hypercholesterolemia is common in heart transplant recipients treated with standard 3-drug immunosuppression and generally develops within the first 2 years after transplantation. However, this complication is not uniform and appears to be most strongly related to previous coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors influencing the success of ventricular defibrillation in man.

To define the factors influencing the success of emergency ventricular defibrillation, we identified 52 patients defibrillated at the University of Iowa Hospital during 1974--1976. Thirty-eight patients were successfully defibrillated at least once; 14 could not be defibrillated, despite multiple attempts. Comparisons between these groups revealed no significant differences in body weight, heart weight, energy per kilogram of body weight and energy per gram of heart weight. Factors that militated against successful defibrillation included a prolonged delay before the first defibrillatory shock (successful 7 +/- 7 minutes (SD); unsuccessful 17 +/- 13 minutes, p less than 0.001), acidosis (successful pH 7.36 +/- 0.22; unsuccessful pH 7.23 +/- 0.12, p = 0.05) and hypoxia (successful PO2 100 + 98 torr; unsuccessful PO2 40 +/- 67 torr; p = 0.06). These three conditions tended to occur together in individual patients. Metabolic factors are important in determining defibrillation success; however, the role of high-energy doses is uncertain.     

Modifications in the closing volume due to the inhalation of tobacco smoke]

Two methods, the one making use of nitrogen and the other of body plethysmography were applied to a group of normal young subjects in order to value the effects of the inhalation of tobacco smoke on the "closing volume". The results obtained with the two methods are different; according to authors, this phenomenon may be explained on the base of the physiopathologic meanings of the closing volume, under the condition to admit that tobacco smoke may promote an early closure and before all disorders in the distribution of the residual volume.