Category - Part 10
The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern: Discussion
The responses also tended to be more protracted than after the central airway deposition of methacholine, and in contrast to the findings after central airway deposition, the decrement of sGaw relative to baseline remained statistically significant (p<0.05) 30 min after the challenge. The three patients who had subnormal sGaw at baseline tended to have a more long-standing bronchoconstriction than the others; sGaw remained at 41 ±11 percent of baseline 30 min after the challenge, while sGaw partially reversed within the same time in the remaining patients (76 ±13 percent of the baseline values). canadianfamilypharmacy
Similar to the response after the deposition of methacholine in trachea and main bronchi, log SDQ increased significantly relative to the baseline immediately after the challenge, peaked at the 30-min measurement, and remained abnormal in the rest of the experiment. Bimodal distributions of the perfusion were recorded in seven patients, and the abnormalities remained 2 h after the challenge in those patients. The maximal decrement in arterial P02 was reached immediately after the challenge, and returned to baseline within 120 min (Table 1), and there was no significant change in arterial PCO2. Thus, the abnormalities in data obtained from the inert gas elimination test and from the measurements of arterial P02 tended to have similar magnitude and time courses in the two separate experiments, with different airway deposition patterns of methacholine.
Continue reading this post…
The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern: Results
The sGaw values tended to return to the baseline within 30 min. However, the bronchocon-striction tended to remain during a longer time period in the three patients who had subnormal baseline values lie, <1.3 [sxkPa]); their mean value of sGaw remained at 27 ±9 percent of baseline (mean±SD), while in those who had normal baseline sGaw, the decrements reversed to reach 90 ± 41 percent of their baseline values within 30 min after the challenge. The perfusion distributions, as assessed by log SDQ, broadened immediately after the challenge (Table 1, p<0.01), and the maximal broadening was recorded 30 min after the inhalation of methacholine in most patients. The abnormality in log SDQ then typically remained throughout the experiment, and log SDQ was significantly elevated relative to the baseline (p<0.05) still at the end of the experiment, 2 h after the challenge. The ventilation distributions tended to increase during the experiment, but the changes relative to baseline did not reach statistical significance. After the challenge, bimodal distributions of the perfusion were recorded in all eight patients, and the bimodality remained until the end of the experiment, 2 h after the challenge. The postchallenge decline in arterial P02 reached nadir immediately after the challenge and reversed to the prechallenge range in the last measurement (Table 1). There were no significant postchallenge changes in arterial PCO2.
Continue reading this post…
The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern: Results
The data were expressed by mean values and SD. The statistical analyses used were Mann-Whitney U test, Wilcoxon matched-paired test, and Spearmans correlation test. A p value of <0.05 was considered to indicate statistical significance.
Baseline Conditions on the Two Experimental Days
Before challenge, sGaw was within the predicted normal values in five of the patients on both study days, and there were no significant interday differences in any of the patients. Narrow unimodal distributions of the ventilation and perfusion were recorded in 10 of 16 measurements performed at baseline the two study days. The Va/Q distributions were mildly abnormal with bimodal distributions of the perfusion in six of the measurements. There were no statistically significant differences in the log SDQ or log SDV values measured at baseline on the twc separate experimental days. Although there were minor decrements from the predicted normal value of the arterial P02 in three of the baseline tests, there were no significant interday differences, and the decrements were present independently of the baseline values of sGaw or the descriptors of Va/Q mismatch. canadian health&care mall
The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern: Radionuclide Imaging
The radioactivity deposited in the lungs was recorded by means of a gamma-camera (Picker SX300, Nuclear Diagnostics, United States). Data were recorded in a 64X64 matrix, and the total activity as well as counts per pixel were recorded in areas corresponding to the lung fields. Regions of interest were defined and selected from the stored images. The regions corresponded to the lower part of trachea and the main bronchi, as well as to two equally large areas of each of the two peripheral lung fields (each 6X10 pixels). The mean counts per pixel were recorded and the areas were postulated to represent radioactivity per tissue unit in central or peripheral airways. A penetration index was formed according to previously published principles by calculating a ratio between the number of counts per pixel in the regions of interest corresponding to the peripheral airway or the trachea and central bronchi. An example of a recorded image is given in Figure 1.
Continue reading this post…
The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern: Experimental Days
Methacholine was mixed with 500 MBq “mTc-DTPA and diluted with saline solution to reach the intended concentration of methacholine and a final volume of 3 ml. The relationship between the amount of radioactivity and methacholine was fixed for each individual in the two experiments. The aerosol was inhaled by tidal breathing, which was maintained during 3 min, and the inhaled doses of methacholine required to induce a 50 percent decline from the baseline values of sGaw were empirically found to correspond to around 150 percent of the cumulated doses of methacholine, found in the individual titration studies. After inhalation of the radiolabeled aerosol, an image of the radioactivity deposited within the lung was made with a gamma camera (see below), and the data were stored on disk. The stored data were then used for analyses of deposited radioactivity in defined regions of interest (see below) and for comparison of the total count rate recorded over the chest during the first and the second experimental days. canadian health mall
The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern: Material and Methods
Five female and three male subjects (mean age, 34 ±8 years) with proved bronchial hyperresponsiveness to inhaled methacholine participated in the study. The patients had a clinical diagnosis of bronchial asthma, and their baseline value of forced expiratory volume in 1 s (FEVi) was at least 80 percent of predicted normal value, and the upper limit of the interstudy day variability in the baseline value of specific airway conductance (sGaw) was set to 15 percent, to allow inclusion to the study. The patients were not receiving any regular treatment with inhaled or oral glucocorticosteroids, and inhaled B-agonists were allowed on an “as required” basis, except for the last 24 h prior to the experiments. Subjects with respiratory tract infections within the last 3 weeks preceding the experiments were excluded from the study, and all subjects denied regular tobacco smoking. Approval of the study was obtained from the Ethics Committee at the University of Uppsala. canadian neighbor pharmacy online
The Bronchial Response, but not the Pulmonary Response to Inhaled Methacholine Is Dependent on the Aerosol Deposition Pattern
Asthma is characterized by increased bronchial responsiveness to a variety of pharmacologic and immunologic stimuli of the bronchial mucosa. Bronchial responsiveness to inhaled parasympathomimetic agents, eg, methacholine, is used in clinical settings to estimate the intensity of the asthmatic process. Stimulation of muscarinic receptors on airway smooth muscle cells and submucosal glands induces airway muscle contraction and mucus secretion. Several animal studies have shown different types of pharmacologic responsiveness in different airway generations, and in humans, less histamine was required to produce bronchoconstriction when deposited in the large, central airways, than when it was distributed in the small, peripheral airways. Heterogeneity of muscarinic receptor localization has also been suggested in humans, and the intra-pulmonary aerosol pattern determined the bronchial responsiveness to methacholine in clinical studies. there