Numerical validation of a new method to assess aortic pulse wave velocity from a single recording of a brachial artery waveform with an occluding cuff.

Recently a new method has been proposed as a tool to measure arterial pulse wave velocity (PWV), a measure of the stiffness of the large arteries and an emerging parameter used as indicator of clinical cardiovascular risk. The method is based on measurement of brachial blood pressure during supra-systolic pressure inflation of a simple brachial cuff [the device is known as the Arteriograph (Tensiomed, Budapest, Hungary)]. This occlusion yields pronounced first and secondary peaks in the pressure waveform, the latter ascribed to a reflection from the aortic bifurcation, and PWV is calculated as the ratio of twice the jugulum-symphysis distance and the time difference between the two peaks. To test the validity of this working principle, we used a numerical model of the arterial tree to simulate pressures and flows in the normal configuration, and in a configuration with an occluded brachial artery. A pronounced secondary peak was indeed found in the brachial pressure signal of the occluded model, but its timing was only related to brachial stiffness and not to aortic stiffness. We also compared PWV's calculated with three different methods: PWVATG (approximately Arteriograph principle), PWVcar-fem (approximately carotid-femoral PWV, the current clinical gold standard method), and PWVtheor (approximately Bramwell-Hill equation). Both PWVATG (R2=0.94) and PWVcar-fem (R2=0.95) correlated well with PWVtheor, but their numerical values were lower (by 2.17+/-0.42 and 1.08+/-0.70 m/s for PWVATG and PWVcar-fem, respectively). In conclusion, our simulations question the working principle of the Arteriograph. Our data indicate that the method picks up wave reflection phenomena confined to the brachial artery, and derived values of PWV rather reflect the stiffness of the brachial arteries.

Experimental and numerical modelling of the ventriculosinus shunt (El-Shafei shunt).

This study assesses malresorptive hydrocephalus treatment by ventriculosinus shunting with the shunt in the antegrade or retrograde position. First, an experimental model of the cerebral ventricles, the arachnoid villi, the cortical veins, and the superior sagittal sinus was built. For this purpose, the compliance of a human cortical vein was measured and then modelled by means of Penrose tubes. The dimensions of the superior sagittal sinus were determined in vivo by measurements on magnetic resonance imaging scans of 21 patients. Second, a numerical model of the cortical veins and the superior sagittal sinus was built. The numerical results were validated with the results from the experimental model. The experimental and numerical pressure difference between the intracranial pressure and the static sinus pressure was small (0-20 Pa) and corresponded to the theoretically expected values. No overdrainage was found in either the antegrade or the retrograde position of the shunt. Blood reflow was only found while mimicking lumbar puncture or changes in position with the experimental model (lowering the intracranial pressure or increasing the sinus pressure rapidly). Optimal results can be obtained with the shunt positioned in the most downstream half of the superior sagittal sinus. The experimental and numerical results confirm the potential of ventriculosinus shunting as therapy for malresorptive hydrocephalus patients. The ventriculosinus shunt thus proves to be a promising technique.

Intranasal and inhaled fluticasone propionate for pollen-induced rhinitis and asthma.

BACKGROUND: Studies suggest that nasal treatment might influence lower airway symptoms and function in patients with comorbid rhinitis and asthma. We investigated the effect of intranasal, inhaled corticosteroid or the combination of both in patients with both pollen-induced rhinitis and asthma. METHODS: A total of 262 patients were randomized to 6 weeks' treatment with intranasal fluticasone propionate (INFP) 200 microg o.d., inhaled fluticasone propionate (IHFP) 250 microg b.i.d., their combination, or intranasal or inhaled placebo, in a multicentre, double-blind, parallel-group study. Treatment was started 2 weeks prior to the pollen season and patients recorded their nasal and bronchial symptoms twice daily. Before and after 4 and 6 weeks' treatment, the patients were assessed for lung function, methacholine responsiveness, and induced sputum cell counts. RESULTS: Intranasal fluticasone propionate significantly increased the percentages of patients reporting no nasal blockage, sneezing, or rhinorrhoea during the pollen season, compared with IHFP or intranasal or inhaled placebo. In contrast, only IHFP significantly improved morning peak-flow, forced expiratory volume in 1 second (FEV1) and methacholine PD20, and the seasonal increase in the sputum eosinophils and methacholine responsiveness. CONCLUSIONS: In patients with pollen-induced rhinitis and asthma, the combination of intranasal and IHFP is needed to control the seasonal increase in nasal and asthmatic symptoms.

Variation of CD8+ T-lymphocytes around the bronchial internal perimeter in chronic bronchitis.

The variation of CD8+ cells has been determined around the internal perimeter of intrapulmonary bronchi in smokers with chronic bronchitis (CB), and the amount of tissue required to confidently estimate the true mean has been calculated. Lung specimens were obtained from 10 smokers with CB. Paraffin sections of intrapulmonary bronchi were immunostained and CD8+ cells counted in the epithelium and subepithelium in up to 10 sequential 1-mm segments around the internal perimeter of each airway. The percentage of counts falling between +/-20% of the final mean was 43.0% for epithelium and 40.9% for subepithelium. In 90% of subjects, the cumulative mean was stable after examination of subepithelial tissue associated with 5 mm of reticular basement membrane. There is considerable variation in the counts of CD8+ cells between adjacent 1-mm airway mucosal segments in chronic bronchitis. In order to achieve a representative count and to maximise statistical power to detect differences between study populations, subepithelial tissue including a minimum of 5 mm of reticular basement membrane length should be examined.

[The relation between morphologic and functional airway changes in bronchial asthma]. / De relatie tussen morfologische en functionele luchtwegveranderingen in bronchiaalastma.

Asthma is currently defined as a chronic inflammatory disorder of the airways. The exact relationship between this inflammatory process and altered airway behavior in asthma remains to be fully established. More specifically, the question remains as to the exact causal relationship between airway inflammation and bronchial hyperresponsiveness (BHR), which constitutes the predominant lung function abnormality in asthma. The two main determinants of BHR are the hypersensitivity and the hyperreactivity of the airways. Hypersensitivity is reflected in a leftward shift of the dose response curve to the bronchoconstrictor effect of agonists such as histamine. More important from a clinical perspective is the hyperreactivity of the airways, which is characterized by excessive airway narrowing. The airway wall consists of three compartments, namely the inner airway wall area between the airway lumen and the smooth muscle layer, the airway smooth muscle layer and the outer airway wall area between the smooth muscle layer and the lung parenchyma. Mathematical models have calculated that changes within each of these compartments can contribute to airway hyperreactivity. Morphometric analysis of asthmatic airways confirm thickening of each of these three airway wall compartments. The contribution of airway inflammation to the thickening of each of these compartments and their relative functional impact on BHR remains to be further elucidated. Asthmatic airways display signs both of the acute and the chronic phase of an inflammatory reaction. The acute allergic inflammation is characterized by the presence of increased amounts of inflammatory cells including eosinophils, mast cells, macrophages, dendritic cells and T helper 2 (Th2) lymphocytes, and is regulated by a complex network of mutually interacting cytokines. The Th2 lymphocyte plays a crucial role within this network. Based, amongst other observations, on in vivo animal models, the hypothesis can be formulated that through the release of a range of cytokines, Th2 cells affect directly airway responsiveness. It would appear that neither crosslinking of IgE and subsequent mast cell degranulation nor eosinophil influx into the airways play a crucial role in this process. Asthmatic airways also display signs of a chronic inflammatory process, that results in more structural alterations, the so-called airway remodeling. This includes increased deposition of collagen and fibronectin, in addition to airway smooth muscle hypertrophy and hyperplasia. In vivo animal models indicate that these structural alterations have a more profound impact on BHR than the acute inflammation. These models also illustrate that depending on the exact extent and location of structural changes throughout the various airway wall compartments, remodeling can enhance but also protect against excessive airway narrowing, despite the presence of acute inflammation. These results illustrate the necessity to take into account the full extent of histological alterations throughout the airway wall, when evaluating the effect of individual cells and cytokines involved in the acute and chronic inflammatory response in asthma.

Murine models of asthma.

In vivo animal models can offer valuable information on several aspects of asthma pathogenesis and treatment. The mouse is increasingly used in these models, mainly because this species allows for the application in vivo of a broad range of immunological tools, including gene deletion technology. Mice, therefore, seem particularly useful to further elucidate factors influencing the response to inhaled allergens. Examples include: the role of immunoregulatory mechanisms that protect against T-helper cell type 2 cell development; the trafficking of T-cells; and the contribution of the innate immunity. However, as for other animal species, murine models also have limitations. Mice do not spontaneously develop asthma and no model mimics the entire asthma phenotype. Instead, mice should be used to model specific traits of the human disease. The present task force report draws attention to specific aspects of lung structure and function that need to be borne in mind when developing such models and interpreting the results. In particular, efforts should be made to develop models that mimic the lung function changes characteristic of asthma as closely as possible. A large section of this report is therefore devoted to an overview of airway function and its measurement in mice.

[Diffuse interstitial lung disorders in systemic diseases]. / Diffuus interstitieel longlijden bij systeemziekten.

Diffuse parenchymal lung disorders (DPLD) can develop in a variety of systemic disorders. Schematically grouped, these include connective tissue disorders, vasculitis, neoplastic disorders, sarcoidosis and a group of inherited or other rare miscellaneous disorders. This overview focuses on sarcoidosis, systemic sclerosis and Churg Strauss vasculitis. Pulmonary involvement occurs in more than 90% of all patients with sarcodosis. Grading into 4 stages is based on the chest radiograph. Forms characterised by an acute clinical onset or a low grade lung involvement have the highest spontaneous remission rate. The cause of sarcoidosis remains unknown. The diagnosis therefore is descriptive, based on the combination of clinical observations, chest X ray, and the histological documentation of non-caseating epitheloid granulomas in tissue biopsies. Treatment with steroids is only indicated if organ involvement leads to functional impairment. Lung fibrosis is the most important complication of both the "limited" and "diffuse cutaneous form" of systemic sclerosis, involving 90% of all patients. The histological pattern is that of "Usual Interstitial Pneumonia" (UIP) or "Non-specific Interstitial Pneumonia" (NSIP). The pathogenesis of the disorder is thought to consist of an abnormal, excessive regenerative response to an auto-immune mediated lung injury. Churg Strauss vasculitis is characterised by asthma, blood eosinophilia and vasculitis of the small vessels. The affected vessels wall shows signs of fibrinoid necrosis and are infiltrated by eosinophils. pANCA (anti-myeloperoxidase) is considered to play a role in the pathogenesis of the disease. Concern has risen that CysLT1 receptor antagonists might induce production of pANCA. To date, this has not been substantiated.

Managing a variable disease.

Asthma varies in severity over time; consequently, treatment regimens must be sufficiently flexible to be adjusted when necessary. At present, inhaled corticosteroids (ICS) remain the cornerstone of asthma therapy and optimal treatment strategies must consider total daily dose and dosing frequency. The dose responsiveness to ICS varies for different indices of asthma. Symptoms and lung function respond readily to low-dose ICS and the dose-response curve is relatively flat. In contrast, the prevention of asthma exacerbations displays a more pronounced dose-response relationship. In mild asthma, once-daily dosing with budesonide is as effective as twice-daily dosing. However, in moderate-to-severe asthma, four-times daily dosing is better than twice-daily dosing for obtaining maximal benefit with minimal side effects. A flexible treatment regimen, consisting of low-dose maintenance treatment combined with high dose and frequently dosed ICS at the earliest sign of an exacerbation, has been shown to be effective. This could be achieved using a single inhaler combination product if the beta(2)-agonist moiety allows for the same flexibility in dosing. Formoterol, with its wide dose range, rapid onset and long duration of effect, has the pharmacological features that permit this versatile, flexible dosing. As a result, Symbicort would seem to offer the flexibility required in a single inhaler for maintenance and reliever purposes in the management of this variable disease.

Dose-related effect of inhaled fluticasone on allergen-induced airway changes in rats.

To examine whether fluticasone propionate (FP) dose-dependently inhibits inflammatory as well as structural changes, Brown Norway rats were sensitised to ovalbumin (OA) on day 0 and 7. From day 14-28, rats were exposed to aerosolised OA (1%) or phosphate buffered saline every 2 days. Thirty minutes before each allergen exposure, animals were pre-treated with aerosolised placebo or FP (0.1, 1 or 10 mg) or prednisolone 3 mg x kg(-1) i.p. At day 29, 0.1 mg FP had no measurable effect, either on inflammatory or structural changes, such as goblet cell hyperplasia and airway wall thickening. The allergen-induced increase in eosinophilic inflammation in bronchoalveolar lavage fluid and in the airway mucosa, as well as increased fibronectin deposition, were inhibited by treatment with FP from a dose of 1 mg onwards. Inhibition of goblet cell hyperplasia and thickening of the airway wall required 10 mg inhaled FP. At this dose, systemic effects were observed. However, for a comparable degree of systemic activity, prednisolone was far less effective at preventing airway changes. The dose of inhaled fluticasone propionate required to inhibit allergen-induced structural alterations was higher than to prevent eosinophil influx, and caused systemic side-effects. However, for a similar systemic activity, prednisolone was ineffective in preventing airway remodelling.

Repeated allergen exposure changes collagen composition in airways of sensitised Brown Norway rats.

Increased or altered collagen deposition in the airway wall is one of the characteristics of airway remodelling in asthma. The mechanisms underlying this increase, and its functional consequences remain to be established further. Representative in vivo animal models might be useful in this respect. In the present study, collagen deposition after prolonged allergen exposure was characterised in the airway wall of Brown Norway rats. Sensitised rats were repeatedly exposed to ovalbumin (OA) or phosphate-buffered saline during 2 and 12 weeks. The deposition of collagen type I, III, IV, V and VI was not altered in animals exposed to OA for 2 weeks. After 12 weeks of OA exposure, more collagen type I was deposited in the inner and outer airway wall and more type V and VI collagen was observed in the outer airway wall. At 12 weeks the number of vessels, identified via type IV collagen staining was not increased, but the total vessel area was. In conclusion, prolonged allergen exposure in sensitised rats is associated with enhanced deposition of type I, V and VI collagens and increased vascularity. This suggests that some aspects of airway remodelling in asthma could be driven by long-term allergen exposure.

Fluticasone inhibits the progression of allergen-induced structural airway changes.

BACKGROUND: Inhaled corticosteroids are widely used as first-line therapy in patients with asthma. The concept of early introduction is more and more accepted. OBJECTIVE: In our rat model of airway remodelling, we investigated whether treatment with inhaled fluticasone propionate can inhibit further progression of established structural airway changes. METHODS: Sensitized Brown Norway rats were exposed to aerosolized ovalbumin (1%) from day 14 to 42. From day 28 to 42, animals were treated with inhaled fluticasone or placebo 30 min before each allergen challenge. One control group was exposed to PBS from day 28 to 42, a second control group throughout the whole experiment. RESULTS: Exposure to ovalbumin during 2 weeks induced structural airway changes, including epithelial cell proliferation, increase in airway wall area and fibronectin deposition. Goblet cell number was increased, although not significantly compared with PBS. Continuing allergen exposure for 2 weeks further enhanced each of these features. In addition, the amount of collagen in the airway wall was enhanced by 4 weeks allergen exposure compared with PBS-exposed animals. These additional increases were inhibited by treatment with fluticasone during the last 2 weeks. CONCLUSION: The progression of established allergen-induced structural airway changes in sensitized rats can be inhibited by treatment with fluticasone.

Interleukin-4 and interleukin-5 gene expression and inflammation in the mucus-secreting glands and subepithelial tissue of smokers with chronic bronchitis. Lack of relationship with CD8(+) cells.

We wished to determine if the inflammatory cells surrounding the airway mucus-secreting glands in chronic bronchitis (CB) were associated with interleukin (IL)-4 and IL-5 mRNA expression and whether the CD8 T cell population expressed these cytokines. Digoxigenin-labeled IL-4 and IL-5 antisense RNA probes were used to detect gene expression in 11 asymptomic smokers (AS), 11 smokers with CB alone with normal lung function, and 10 smokers with chronic bronchitis and coexisting chronic obstructive pulmonary disease (CB+COPD; FEV(1)% of predicted of 43-77% and FEV(1)/ FVC of 51-68%). There were approximately three times as many IL-4 than IL-5 mRNA(+) cells. The highest number of IL-4 mRNA(+) cells were in the submucosal glands of the CB group with normal lung function (216/mm(2)), significantly higher than the values in either the AS (63/mm(2)) or the CB+COPD (87/mm(2)) groups, respectively (p < 0.01). There were similar group differences when the total numbers of inflammatory cells were compared. Accordingly, there was a positive correlation between the number of IL-4 mRNA(+) cells and the total number of inflammatory cells in both the subepithelium and glandular compartments (r = 0.60; p = 0.01 and r = 0.70; p = 0.02, respectively). There were no significant associations between the numbers of CD8(+) and IL-4 or IL-5 mRNA(+) cells. Of 1328 IL-4(+) and 1404 CD8(+) cells counted none was double labeled. Of 727 IL-5(+) and 1569 CD8(+) cells, none was double labeled. In contrast, as a positive control, 34% of tumor necrosis factor (TNF)-alpha(+) cells were also CD8(+) and 15% of CD8(+) cells were TNF-alpha positive. Thus, cells other than the CD8(+) phenotype produce IL-4 and IL-5 in CB. We conclude that there is increased inflammation and IL-4 gene expression in the mucus-secreting glands and the airway mucosa of smokers with bronchitis: both are lower in those with CB and coexisting COPD suggesting that airway inflammation in CB is reduced when airway obstruction develops.

Distribution of type-1 and type-2 angiotensin receptors in the normal human lung and in lungs from patients with chronic obstructive pulmonary disease.

This study was designed to examine the cellular distribution of the angiotensin II type-1 (AT1) and type-2 (AT2) receptors in the normal human and pathological human lung. Riboprobes were prepared against specific portions of each receptor DNA and labelled with FITC for detection using an anti-FITC antibody in combination with the alkaline phosphatase-anti-alkaline phosphatase technique and new Fuchsin. These were used to detect the presence of receptor mRNA in the lung. Specific antibodies were used to detect receptor protein in cells by immunocytochemistry. Image analysis was used in order to semi-quantify receptor density. AT1 receptor mRNA and protein were localised on vascular smooth muscle cells, macrophages and in the stroma underlying the airways epithelium probably relating to underlying fibroblasts. The AT1 receptor protein was not expressed in the epithelium although there was a low level of mRNA. In contrast, AT2 receptor RNA and protein was observed in the epithelium, with strong staining on the bronchial epithelial cell brush border and also on many of the underlying mucous glands. The AT2 receptor was also present on some endothelial cells. These findings were supported by the presence of mRNA in each case. In patients with chronic obstructive pulmonary disease, there was a five- to sixfold increase in the ratio of AT1 to AT2 receptors in the regions of marked fibrosis surrounding the bronchioles. This correlated well with the reduced lung function as expressed by the forced expiratory volume.

New anti-asthma therapies: suppression of the effect of interleukin (IL)-4 and IL-5.

Asthma is currently defined as a chronic inflammatory disorder of the airways. The central role of allergen-specific Th2 cells in the regulation of this mucosal airway inflammation has been highlighted. Hence, there is large interest in the therapeutic potential of an anti-Th2 cell approach. One of the strategies which has been developed, is to inhibit the effect of interleukin (IL)-4 or IL-5, two main Th2 cell derived cytokines. Interleukin-4 is pivotal in the pathogenesis of allergic disorders through its wide range of effects. An important observation, especially during secondary antigen exposure, is the possible redundancy with IL-13. Both cytokines share common elements in their receptor and intracellular signalling pathway. As a result, compounds can be developed that selectively inhibit the effect of either IL-4 or IL-13, or alternatively, by interfering with the common pathway, inhibit the effect of both cytokines. Eosinophils are generally seen as a particularly harmful element in the allergic inflammation. The importance of IL-5 on eosinophil biology has clearly been established. Conversely, in man, the biological effects of IL-5 are largely limited to eosinophil function. Therefore, IL-5 antagonists offer the unique opportunity of selectively neutralizing the effect of eosinophils. Several strategies have now been developed that successfully inhibit the biological effect of interleukin-4 or interleukin-5. Some of these compounds have proven to be biologically active in man. The challenge now is to establish their therapeutic role in asthma.