Dynamics of 'Technegas' deposited in the lung

In tomographic Technegas ventilation studies, the deposited aerosol should be stable. The aim of this study was to investigate the stability of deposited Technegas in severely obstructed patients and in healthy volunteers. Six emphysematous patients and five healthy volunteers were studied. Anterioposterior (AP) and posterioanterior (PA) dynamic images of ventilation (120 frames, 1 frame.min-1) were acquired after inhalation of 99mTc-Technegas' in the supine position. The time-activity curve of the whole lung showed two phases in the emphysematous patients as well as in the healthy volunteers. The activity decreased rapidly in the first phase, then reached almost a constant level (the second phase) after approximately 50 min. The logarithms of both the first phase and the second phase were close to straight lines. The half-time of the first phase was approximately 9 min. No systematic differences in 'Technegas' clearance rate were found between central regions and peripheral regions and between high count rate regions and normal count rate regions. Pertechnegas contamination was subsequently detected, and we conclude that the rapid first phase is probably due to clearance of Pertechnegas. When stable Technegas is required, we suggest that data acquisition should start about 50 min after inhalation.     

Does undernutrition contribute to diaphragm weakness in patients with severe COPD?

BACKGROUND AND AIMS: The assumption that undernourishment contributes to diaphragm weakness in chronic obstructive pulmonary disease (COPD) remains unproven. METHODS: We, therefore, studied diaphragm strength, measured as transdiaphragmatic pressure during a maximal voluntary sniff (Sn P(di)) and cervical magnetic stimulation (Tw P(di)), in two groups of 10 patients with severe COPD. The groups had equally severe COPD as judged by FEV(1) and thoracic gas volume (V(tg)). The malnourished group had a mean body mass index (BMI) of 17.3 kg/m(2) compared with 27 kg/m(2) for the normally nourished group (mean difference -9.7 kg/m(2); 95% confidence intervals -6.8 to -12.6 kg/m(2),P <0.0001). RESULTS: There was no significant difference between Tw P(di) (mean difference 2.1 cm H(2)O; 95% CI-3 to + 7.4 cm H(2)O, P=0.39) or Sn P(di) (mean difference -2.4 cm H(2)O; 95% CI-21 cm H(2)O to +16 cm H(2)O,P =0.8). CONCLUSION: We conclude that undernourishment of the severity studied does not contribute to diaphragm weakness in severe COPD.     

Non-uniform lung elastic properties and the slope of the alveolar plateau

Dispersion of elastic properties within the lungs may contribute to the creation of a sloping alveolar plateau of the single-breath N2 washout curve. In this study we have systematically explored the behaviour of a simple two-compartment lung model with non-uniform pressure-volume characteristics. The inhomogeneity was expressed in terms of the ratio between the shape constants (k1/k2) of the compartmental pressure-volume curves and the ratio between compartmental RV/TLC (R-RV/TLC). The model simulations indicate that normal slope magnitudes can be achieved with a moderate degree of inhomogeneity (k1/k2 and R-RV/TLV = 2). The model simulations also show that a phase II-like shape of the curve--of non dead space origin--may occur and furthermore that single-breath TLC determinations increasingly underestimate true TLC as the R-RV/TLC deviates from unity. For a given degree of inhomogeneity, the model predicts the slope to increase with overall RV/TLC and k but decrease with TLC. The relations between these overall factors and the slope of phase III are also found in a patient group, where these factors explain approximately 61% of the slope variance.     

Inhomogeneity in planar ventilation scintigraphy of emphysematous patients

The aim of this study was to develop and evaluate a method for the quantification of inhomogeneity in ventilation scintigraphy. Ten healthy volunteers and 10 emphysematous patients were investigated. Anteroposterior (AP) and posteroanterior (PA) images of planar ventilation scintigraphy were acquired. Lung regions of interest (ROI) were obtained by manual delineation of the lung contours and then divided into several 10-pixel-high horizontal-stripe regions. By allowing for the statistical noise of the pixel count rate, the biological coefficient of variation (CVB) of the pixel counts in each stripe region was calculated. The apex-to-base distribution of the CVB in the emphysematous lungs dispersed largely and with higher values than the corresponding distribution in the healthy lungs. The mean values of the CVB (MCVB), the ranges of the CVB (RCVB) and the maximum values of the CVB (MAXCVB) in the stripe regions in emphysematous lungs were significantly higher than the corresponding ones in the healthy lungs (all P<0·001). The intraobserver variations of the MCVB, RCVB and MAXCVB (calculated using the standard deviations of the differences) were less than 2·3% units, 5·2% units and 3·9% units respectively. The corresponding values for interobserver variation were 5·7% units, 6·1% units and 6·4% units. A systematic decrease in lung ROI size, i.e. inclusion of successively less of the lung edge, resulted in a linear decrease of 1·7% units in the MCVB and MAXCVB of both emphysematous and normal lungs. In conclusion, the stripe-region method is a reliable tool for the quantification of inhomogeneity in the planar ventilation scintigraphy.     

Analysis of helper activity on pokeweed mitogen- and interleukin 2-driven immunoglobulin synthesis by neoplastic T4+ cells.

The neoplastic T cells of a series of seven patients with chronic T-cell neoplasia were tested for helper activity on pokeweed mitogen (PWM)-induced and interleukin 2 (IL-2)-induced Ig synthesis. The neoplastic T cells of all patients had a T3+4+8-11+I1- phenotype but differed in expression of the 3A1 antigen. The neoplastic T cells of three patients had helper activity on both PWM- and IL-2-driven Ig synthesis, and in addition produced IL-2 in response to PWM stimulation. Two of these patients had hypergammaglobulinemia. In contrast, the neoplastic T cells in the remaining four patients did not produce IL-2 and did not support PWM-driven Ig synthesis. The T4+ cells of these four patients, however, provided excellent helper activity on IL-2-driven Ig synthesis. These findings emphasize the role of IL-2 in T cell-dependent Ig synthesis and clearly show that IL-2 production is required for helper activity in the PWM-driven system. It is concluded that the combined use of PWM- and IL-2-driven Ig synthesis systems allows separate analysis of IL-2 production and T-helper activity in health and disease.     

A simple pressure calibrator.

A simple reliable, easy-to-use, and inexpensive device for obtaining any predetermined static gas pressure within +/- 35 cm H2O is described. It is suitalbe as a calibrator for pressure transducers as used in respiratory physiology. It is more convenient to use than an ordinary U-tube.     

Post-polio lung function.

Post-polio patients sometimes complain about the occurrence of breathing difficulties decades after the polio infection. We have examined 40 post-polio patients who have had respiratory or non-respiratory poliomyelitis for at least 30 years in an attempt to elucidate whether hypoventilation is common and to what extent certain symptoms and simple lung function tests are related to hypoventilation or incipient hypoventilation. We measured arterial blood gases, vital capacity (VC), maximal expiratory and inspiratory pressures (MEP, MIP) and CO2 rebreathing response. Symptoms were assessed by a yes/no questionnaire. Six patients required respiratory assistance at the onset of the disease. At present, two require nocturnal assisted ventilation. Two patients showed manifest hypoventilation; one of which required night-time ventilator, whereas the other patient had not required ventilatory assistance even at the onset of the disease. Significant correlation (p less than 0.05) was found between arterial carbon dioxide tension (a-PCO2) and VC, MEP and ventilation increase during CO2 rebreathing. A significantly higher a-PCO2 was found among those who required respiratory assistance at the onset of the disease, who admitted headache and who felt the cough ineffective. Low VC and low ventilatory increase during CO2 rebreathing and the presence of headache explained 45% of the variation in a-PCO2 in a multiple regression analysis. We conclude that manifest hypoventilation is rare in this unselected material of post-polio patients and that a vital capacity below 45-50% of predicted normal and the presence of frequent headaches indicate an increased risk to develop hypoventilation.     

Assessment of the exposure of breast milk to persistent organic pollutants in Latvia

According to the National Implementation Plan on persistent organic pollutants (POP) for the years 2004-2020 the situation on POP was actualised in Latvia. The aim of the study was to assess the contamination of breast milk with polychlorinated biphenyls (PCB), polychlorinated dibenzodioxins, dibenzofurans (PCDD/PCDF) and some pesticides. Breast feeding mothers (together 30) were selected from probably polluted area, and a control group on the basis of WHO criteria for donor selection. The concentration of POP in milk was detected by gas chromatography with HRGC/HRMS, HRGC/ECD and GC/ECD detection after extraction of milk fat and purification. The results of the survey show comparability of both groups in age, weight, habits, occupation as well as age of the children and the weight at birth and at the time of collecting the samples. PCB were not observed in 15.9%, PCDD/PCDF in 6.6% and pesticides in 14% analyses of the target group and in 26.3%, 7% and 8.6% analyses correspondingly of the control group. The concentration of 18 detected PCB, 17 detected PCDD/PCDF and 8 chlorinated pesticides and its metabolites varied in wide range and the differences of mean values within groups were not statistically significant (p>0.05). The concentration of POPs corresponds to lowest levels detected in European countries. The concentration of dioxine-like PCBs and PCDD/PCDF according to toxicity equivalents does not exceed the WHO accepted level of 15 TEQ pg/g milk fat.     

Demonstration of dilatation of peripheral airways

Summary. To investigate the ability of various lung-function tests to demonstrate dilatation of peripheral airways, ten asthmatics inhaled increasing doses of a f2-agonist by two different and controlled techniques. Low inspiratory flow with a long post-inspi-ratory pause favoured peripheral deposition, and a high inspiratory flow with a short post-inspiratory pause favoured central deposition of drug in the airways. Ordinary spirometry, maximum expiratory flow rates after breathing air as well as a helium-oxygen mixture, a single breath N₂-test and resistance of the respiratory system were obtained before and after each of five terbutaline doses with both inhalation techniques. By using a double-dummy technique, the study could be performed double blinded. Effects were compared at doses giving equal effects on PEF, assumed to represent equal deposition of bronchodilator and effects on central airways. At such ‘iso A PEF doses’, particularly FVC and the slope of phase III of the N₂-test improved more following the slow inhalation technique. It is concluded that changes in those tests reflect dilatation in peripheral airways in asthmatics.,