Vasomotion influences airflow in peripheral airways

Anti-angiogenic Properties of Bevacizumab Improve Respiratory System Inflammation in Ovalbumin-Induced Rat Model of Asthma

Studies on the bronchial vascular bed have revealed that the number of blood vessels in the lamina propria and under the mucosa of the lung tissue increases in patients suffering from mild to severe asthma. Thus, in this study, a new strategy was employed in respiratory system disorders by angiogenesis inhibition in an ovalbumin (OVA)-induced rat model of asthma. Twenty-one male Wistar albino rats, 8 weeks old, were randomly divided into three groups (n = 7 in each group), including (1) control group, (2) OVA-treated group, and (3) OVA + Bmab (bevacizumab drug). On days 1 and 8, 1 mg of OVA and aluminum hydroxide in sterile phosphate-buffered saline (PBS) were intraperitoneally injected to rats in groups 2 and 3. The control group was only subject to intraperitoneal injection of saline on days 1 and 8. One week after the last injection, the rats (groups 2 and 3) were exposed to OVA inhalation for 30 min at 2-day intervals from days 15 to 25. After sensitization and challenge with OVA, the OVA + Bmab group (group 3) were treated with a 5 mg/kg bevacizumab drug. Genes and protein expression of IL-1β and TNF-α and the expression of vascular endothelial growth factor (VEGF) protein were assessed by real-time PCR and immunohistochemistry respectively, in lung tissue. OVA exposure increased mucosal secretion and inflammatory cell populations in lung tissue and OVA-specific IgE level in serum. Also, VEGF and cytokine factor expression were significantly elevated in the OVA-induced asthma model (p ≤ 0.05). However, rats in OVA + Bmab group showed significantly a decrease in VEGF and IL-1β and TNF-α genes as well as proteins (p ≤ 0.05). The results showed that bevacizumab efficiently diminished bronchial inflammation via downregulation of VEGF expression, followed by inflammatory cells population and cytokines reduction. Angiogenesis inhibition in rats with induced asthma not only suppresses the inflammatory process through blocking VEGF expression but also inhibits the development of new blood vessels and progressing asthmatic attacks.

Distinguishing Chronic Thromboembolic Pulmonary Hypertension From Other Causes of Pulmonary Hypertension Using CT

OBJECTIVE

The purpose of this study was to discern imaging findings that separate chronic thromboembolic pulmonary hypertension (CTEPH) from other causes of pulmonary hypertension (PH).

MATERIALS AND METHODS

A total of 143 patients with proven PH (group 1, pulmonary arterial hypertension; group 2, PH due to left heart disease; group 3, PH due to lung disease; group 4, CTEPH; and group 5, PH due to unclear or multifactorial mechanisms) underwent MDCT angiography. The CT images were assessed for the presence of chronic pulmonary embolism (PE), disparity in segmental vessel size, mosaic perfusion, parenchymal densities, bronchial dilatation, and collateral arteries.

RESULTS

The frequencies of vascular signs of chronic PE, disparity in segmental vessel size, mosaic perfusion, parenchymal densities, bronchial collateral arteries, and bronchial dilatation were statistically significantly higher in patients with CTEPH than in patients with nonthromboembolic PH. Vascular signs of chronic PE, mosaic perfusion, parenchymal densities, and bronchial dilatation without bronchial wall thickening were significantly more frequent in patients with CTEPH than in patients in groups 1, 2, 3, and 5. There was no significant difference in the frequencies of bronchial collateral arteries between patients with CTEPH and patients in groups 3 and 5.

CONCLUSION

Most patients with CTEPH have direct vascular signs of chronic PE. Secondary signs include disparity in segmental vessel size, mosaic perfusion pattern, parenchymal densities, collateral bronchial arteries, and bronchial dilatation, which help distinguish CTEPH from other causes of PH.

Effect of supine posture on airway blood flow and pulmonary function in stable heart failure

BACKGROUND

The aim of this study was to determine the relationship between body position, pulmonary function (PF) and bronchial blood flow (Q(aw)) in a group of heart failure (HF) and control subjects.

METHODS

Thirty-six subjects were studied: 24 stable, ambulatory HF patients (HF: LVEF=27±6%, age=65±9 yr) and 12 age- and sex-matched controls (CTRL: LVEF=60±7%, age=62±8 yr). Measures of Q˙(aw) (soluble gas method) and PF were collected upright and following 30min in the supine position.

RESULTS

Q˙(aw) was similar between groups and remained unchanged with body position. Declines in forced vital capacity (FVC) and forced expiratory volume in 1s (FEV1) with the supine position were observed in both groups; declines in forced expiratory flow 25-75% (FEF(25-75)) and FEF 75% (FEF75) with the supine position were observed in the HF group only. Changes in Q˙(aw) were related to changes in PF only in the HF patient groups (ΔFVC, % predicted, r = -0.45, p<0.04, ΔFEV1 r = -0.61, p<0.01, ΔFEV1% predicted, r = -0.45, p<0.04).

CONCLUSION

These data demonstrate that relationships between postural changes in Q˙(aw) and PF exist only in the HF population and that the bronchial circulation may contribute to postural PF decline in HF.

CT findings in diseases associated with pulmonary hypertension: a current review

Pulmonary hypertension may primarily affect either the arterial (precapillary) or the venous (postcapillary) pulmonary circulation. Pulmonary arterial hypertension may be idiopathic or arise in association with chronic pulmonary thromboembolism; pulmonary embolism caused by tumor cells, parasitic material, or foreign material; parenchymal lung disease; liver disease; vasculitis; human immunodeficiency virus infection; or a left-to-right cardiac shunt. Its histologic characteristics include vascular changes-medial hypertrophy, intimal cellular proliferation, intraluminal thrombosis, and the development of plexiform lesions-that manifest primarily in the muscular pulmonary arteries. Features of pulmonary arterial hypertension that may be seen at computed tomography (CT) are central pulmonary artery dilatation, abrupt narrowing or tapering of peripheral pulmonary vessels, right ventricular hypertrophy, right ventricular and atrial enlargement, dilated bronchial arteries, and a mosaic pattern of attenuation due to variable lung perfusion. Pulmonary venous hypertension may result from pulmonary veno-occlusive disease, pulmonary venous compression by extrinsic lesions (eg, mediastinal fibrosis), left-sided cardiac disease, or pulmonary vein stenosis. Its histologic hallmarks include venous intimal cellular proliferation, medial hypertrophy, and thickening of the internal elastic lamina; capillary congestion and proliferation; interlobular septal thickening; lymphatic dilatation; and, sometimes, venous infarction and vascular changes characteristic of pulmonary arterial hypertension. CT scans in patients with pulmonary venous hypertension show pulmonary interstitial and alveolar edema with signs of pulmonary arterial hypertension. High-resolution CT with standard axial and angiographic acquisitions is useful for identifying underlying disorders and differentiating among the various causes of secondary pulmonary hypertension.

Targeting abnormal airway vascularity as a therapeutical strategy in asthma

Asthma is a chronic inflammatory disease of airways, characterized by airway hyperresponsiveness and airflow limitation with acute bronchoconstriction, swelling of the airway wall, chronic mucus plug formation and airway wall remodelling. Functional and structural changes in the vasculature of asthmatic airways have been documented, and the signalling mechanisms are complex and have recently attracted much attention. The vascular changes may affect inflammatory cell recruitment, airway hyperresponsiveness and the regulation of airway calibre, and further, the level of disease control. Many critical factors are involved in the pathophysiological regulation of vascular changes in bronchial asthma, and the actions of these factors must be very carefully orchestrated. By better understanding the complicated actions of each factor, we may be able to advance further in asthma treatment.

Does the bronchial circulation contribute to congestion in heart failure?

Pulmonary congestion is a hallmark feature of heart failure and is a major reason for hospital admissions in this patient population. Heart failure patients often demonstrate restrictive and obstructive pulmonary function abnormalities; however, the mechanisms of these changes remain controversial. It has been suggested that the bronchial circulation may play an important role in the development of these pulmonary abnormalities and in the symptoms associated with pulmonary congestion. Congestion may occur in the bronchial circulation from either a marked increase in flow or an increase in blood volume but with a reduction in flow due to high cardiac filling pressures and high pulmonary vascular pressures (a stasis like condition). Either may lead to thickened bronchial mucosal and submucosal tissues and reduced airway compliance resulting in airway obstruction and restriction and a lack of airway distensibility. These structural changes may contribute to "cardiac asthma" and dyspnea, characteristic features common in HF patients. Thus the bronchial circulation may be a potential target for therapeutic interventions. The aim of this paper is to review factors governing the control of the bronchial circulation, how bronchial vascular conductance may change with HF and to pose arguments, both supporting and in opposition to the bronchial circulation contributing to congestion and altered pulmonary function in HF. We ultimately hypothesize that the engorgement of the bronchial circulatory bed may play a role in pulmonary function abnormalities that occur in HF patients and contribute to symptoms such as orthopnea and exertional dyspnea.

Congenital absence of the right interlobar pulmonary artery: HRCT findings

We report a case of unilateral idiopathic pulmonary fibrosis-like changes in the right middle and lower lobe without lung volume changes and with normal upper lobe owing to congenital absence of the right interlobar pulmonary artery on chest computed tomography.

Asthma remission in a patient with rheumatoid arthritis while on antiangiogenesis therapy during a rheumatoid arthritis trial demonstrated by forced oscillation and spirometry

Asthma is a chronic inflammatory condition. An integral part of the inflammation is angiogenesis (neovascularization). This report describes a patient with rheumatoid arthritis (RA) and moderately severe asthma despite maintenance on inhaled corticosteroids (ics) and intermittent systemic steroids (ss). While enrolled in a clinical trial for RA employing MEDI-522 (Vitaxin), her asthma symptoms remitted substantially, with significant improvement in spirometry and airflow resistance measured by forced oscillation. The patient was able to discontinue ics and required no ss while taking MEDI-522. After termination of the clinical trial, the patient's asthma symptoms again increased and required reinstitution of ics for control.

Continuous wavelet transform of laser-Doppler signals from facial microcirculation reveals vasomotion asymmetry

Facial laser Doppler flux (FLDF) consists of a mean value and complex oscillatory components called vasomotion. Vasomotion can be expressed as spectral amplitudes (SA) after the application of continuous wavelet transform. Vasomotion is influenced by cardiac activity (frequency interval I), respiration (interval II), intrinsic myogenic activity (interval III), neural mechanisms (interval IV) and endothelial mechanisms (intervals V and VI). Asymmetry of FLDF mean value was previously documented and hereby we present homogeneity assessment for FLDF vasomotion. Mean FLDF (p<0.001), total SA (p<0.001) and SA within frequency intervals I-VI were significantly higher in both cheeks compared to forehead. Total SA (p=0.009) and SA within frequency intervals I (p=0.041), II (p=0.005), III (p=0.009), IV (p=0.001) and V (p=0.036) were significantly higher in right than in left forehead. Human face is a heterogeneous microvascular region. Angiographic characteristics of deep horizontal sub-dermal plexus, endothelial and vascular smooth muscle cell heterogeneity, and plasticity of the microvasculature, autonomic asymmetry and facial neuropsychological asymmetry are possible causes of microvascular asymmetry. The origin and significance of microvascular imbalance need to be elucidated further.

Efficacy of nitroglycerin inhalation in reducing pulmonary arterial hypertension in children with congenital heart disease

BACKGROUND

There has been a renewed interest in nitric oxide donor drugs, such as nitroglycerin, delivered by the inhalational route for treatment of pulmonary arterial hypertension (PAH). We investigated the acute effects of inhaled nitroglycerin on pulmonary and systemic haemodynamics in children with PAH associated with congenital heart disease.

METHODS

Nineteen children with acyanotic congenital heart disease and a left to right shunt with severe PAH, undergoing routine diagnostic cardiac catheterization were included in this study. Systolic, diastolic and mean systemic as well as pulmonary artery pressures, right atrial pressure and pulmonary capillary wedge pressure (PCWP) were recorded and systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI) were calculated at room air, following 100% oxygen as well as after nitroglycerin inhalation in all patients.

RESULTS

Systolic, diastolic and mean pulmonary artery pressure and PVRI decreased significantly, whereas heart rate, systolic, diastolic and mean systemic arterial pressure, PCWP and SVRI did not change significantly following 100% oxygen or inhalation of nitroglycerin.

CONCLUSION

Inhaled nitroglycerin significantly decreases systolic, diastolic and mean pulmonary artery pressure as well as PVRI without affecting systemic haemodynamics, and thus can be used as a therapeutic modality for acute reduction of PAH in children with congenital heart disease.

Inhaled corticosteroids reduce asthma-associated airway hyperperfusion through genomic and nongenomic mechanisms

Inhaled corticosteroids have both genomic and nongenomic actions on the tracheobronchial (airway) vasculature in patients with bronchial asthma. Genomic actions involve the activation or repression of target genes associated with inflammation, and reduce inflammatory hyperperfusion in the airway. In contrast, nongenomic actions are mediated by rapid cellular mechanisms, and induce transient vasoconstriction. This article reviews recent progress on the mechanisms by which inhaled corticosteroids reverse inflammatory blood flow changes in the airway in asthma.

Fibrosing mediastinitis with peripheral airway dilatation and central pulmonary artery occlusion

We present a case of fibrosing mediastinitis causing peripheral airway abnormalities on CT consisting of bronchial dilatation and wall thickening due to longstanding central pulmonary artery obstruction. The peripheral airway dilatation is similar in appearance to that which has been described in patients with chronic pulmonary embolism.

HRCT Findings of Proximal Interruption of the Right Pulmonary Artery

The purpose of this study is to present the characteristic HRCT findings of the lung parenchyma in patients with proximal interruption of the right main pulmonary artery. HRCT findings of proximal interruption of the right pulmonary artery demonstrated reticular opacities, septal thickening, subpleural consolidation, cystic lung changes, and pleural thickening in all 5 patients; bronchial dilation and bronchial wall thickening in 4 patients; and subpleural ground glass opacity (GGO) in 3 patients. The changes may be caused by absent pulmonary artery perfusion and development of systemic vessel collateralization.

Oscillation mechanics of the human lung periphery in asthma

To more precisely measure the mechanical properties of the lung periphery in asthma, we have developed a forced oscillation technique that applies a broad-band flow signal through a wedged bronchoscope. We interpreted the data from four healthy and eight mildly asthmatic subjects in terms of an anatomically accurate computer model of the wedged segment. There was substantial overlap in impedance between the two groups, with resistance (R) showing minimal frequency dependence and elastance (E) showing positive and negative frequency dependence across subjects. After direct instillation of methacholine, R rose in both groups, but compared with healthy subjects, the asthmatic subjects displayed upward, parallel shifts in their dose-response curves. The baseline frequency-response patterns of E were enhanced after methacholine. Frequency dependencies of R and E were well reproduced in two normal subjects by a computational model that employed rigid airways connected to constant-phase tissue units but were better reproduced in the other two normal and three asthmatic subjects when the model employed heterogeneous, peripheral airway narrowing and compliant airways. To capture the frequency dependencies of R and E in the remaining five asthmatic subjects, the model was modified by increasing airway wall stiffness. These results indicate that the lung periphery of mildly asthmatic subjects is not well distinguished from that of healthy subjects by measurement of mechanical impedance at baseline, but group differences are seen after challenge with methacholine. Modeling of the response suggests that variable contributions of airway narrowing and wall compliance are operative in determining overall mechanical impedance of the lung periphery in humans with asthma, likely reflecting the functional consequences of airway inflammation and remodeling.

Effects of pulmonary vascular pressures and flow on airway and parenchymal mechanics in isolated rat lungs

Changes in pulmonary hemodynamics have been shown to alter the mechanical properties of the lungs, but the exact mechanisms are not clear. We therefore investigated the effects of alterations in pulmonary vascular pressure and flow (Q(p)) on the mechanical properties of the airways and the parenchyma by varying these parameters independently in three groups of isolated perfused normal rat lungs. The pulmonary capillary pressure (Pc(est)), estimated from the pulmonary arterial (Ppa) and left atrial pressure (Pla), was increased at constant Q(p) (n = 7), or Q(p) was changed at Pc(est) = 10 mmHg (n = 7) and at Pc(est) = 20 mmHg (n = 6). In each condition, the airway resistance (Raw) and parenchymal damping (G) and elastance (H) were identified from the low-frequency pulmonary input impedance spectra. The results of measurements made under isogravimetric conditions were analyzed. The changes observed in the mechanical parameters were consistent with an altered Pla: monotonous increases in Raw were observed with increasing Pla, whereas G and H were minimal at Pla of approximately 7-10 mmHg and increased at lower and higher Pla. The results indicate that Pla, and not Ppa or Q(p), is the primary determinant of the mechanical condition of the lungs after acute changes in pulmonary hemodynamics: the parenchymal mechanics are impaired if Pla is lower or higher than physiological, whereas airway narrowing occurs at high Pla.

Responsiveness of canine bronchial vasculature to excitatory stimuli and to cooling

Changes in bronchial vascular tone, in part due to cooling during ventilation, may contribute to altered control of airflow during airway inflammation, asthma, and exercise-induced bronchoconstriction. We investigated the responses of canine bronchial vasculature to excitatory stimuli and cooling. Electrical stimulation evoked contractions in only some (8 of 88) tissues; these were phentolamine sensitive and augmented by N(omega)-nitro-L-arginine. However, sustained contractions were evoked in all tissues by phenylephrine [concentration evoking a half-maximal response (EC(50)) approximately 2 microM] or the thromboxane A(2) mimetic U-46619 (EC(50) approximately 5 nM) and less so by beta,gamma-methylene-ATP or histamine. Cooling to room temperature markedly suppressed ( approximately 75%) adrenergic responses but had no significant effect against U-46619 responses. Adrenergic responses, but not those to U-46619, were accompanied by an increase in intracellular Ca(2+) concentration. Chelerythrine (protein kinase C antagonist) markedly antagonized adrenergic responses (mean maxima reduced 39% in artery and 86% in vein) but had no significant effect against U-46619, whereas genistein (a nonspecific tyrosine kinase inhibitor) essentially abolished responses to both agonists. We conclude that cooling of the airway wall dramatically interferes with adrenergic control of bronchial perfusion but has little effect on thromboxane-mediated vasoconstriction.

Pulmonary capillary blood volume in hyperpnea-induced bronchospasm

Reactive hyperemia of the bronchial circulation has been postulated to contribute to the airway narrowing that occurs following exercise or hyperpnea in subjects with asthma with hyperpnea-induced bronchospasm (HIB). Changes in lung parenchymal mechanics also occur in HIB, including increases in peripheral airway resistance. Since the peripheral airways and lung parenchyma are supplied by the pulmonary circulation, and changes in the pulmonary circulation could alter airway resistance or tissue mechanics, we hypothesized that pulmonary capillary blood flow would increase in association with HIB, resulting in increases in pulmonary capillary blood volume (VC). We measured VC by using two test gases of varying oxygen concentration to determine the diffusing capacity of the lung for carbon monoxide (DL(CO)) before and after a period of hyperpnea in 13 subjects with asthma with HIB and 10 control subjects without asthma. Despite subjects with asthma having a significant fall in FEV(1) following hyperpnea compared with control subjects (DeltaFEV(1) = -26 +/- 12 versus -4 +/- 4%, mean +/- SD, p < 0.001), there was no change in the DL(CO) or VC from baseline values. We conclude that pulmonary capillary blood volume does not change following hyperpnea, and therefore that changes in pulmonary blood flow are not associated with HIB.

Partitioning of alterations in pulmonary mechanics due to vascular engorgement in piglets

The aim of our study was to determine the effects of pulmonary vascular engorgement on airways and pulmonary tissues in juvenile animals before and after methacholine (Mch)-induced changes in lung function. Five anesthetized, paralyzed, and thoracotomized piglets were studied before and during pulmonary vascular engorgement, induced by inflating a left atrial balloon catheter and by calculating respiratory mechanics from measurements of airway opening (Pao) and alveolar pressures (PA), respiratory flow (V'), and volume (V) recorded during mechanical ventilation, using the multilinear regression technique. A maximal increase of 15 mmHg in pulmonary artery pressure (Ppa) resulted in a mean increase in total lung elastance (EL) of 28.6% and in total lung resistance (RL) of 14.9%. Mch increased EL by 21.7% and RL by 29.0%. Inflation of the left atrial balloon with an associated increase in Ppa by 15 mmHg in the presence of Mch resulted in an increase in EL by a further 12.4% (to 135.4% of baseline) and in RL by a further 9.0% (to 139.5% of baseline). The change in RL was associated with a qualitatively similar change in both tissue resistance (Vti) and airway resistance (Raw) before and after Mch-induced changes in lung function. We conclude that increasing pulmonary vascular pressures, by increasing left partial pressure, alters lung function in juvenile animals by altering the mechanical properties of both airways and lung tissues. The methods used in the present study allow a direct assessment of the site of action of vascular engorgement in the lungs and provide a useful model for studying this phenomenon further.

Vagal reflex is not responsible for changes in airway and lung tissue mechanics due to vascular engorgement in young piglets

Eleven open-chest piglets were studied to examine the effects of vascular engorgement on partitioned airway and lung tissue mechanics, and to investigate the role of vagal denervation on lung function during engorgement. Alveolar pressure was measured using alveolar capsules. Pulmonary elastance (EL) and resistance (RL), airway (Raw), and tissue (Vti) resistance were calculated during mechanical ventilation. Acute fluid administration with polygeline (10 mL/kg boluses up to a total of 30 mL/kg) resulted in an increase of RL with increases in both Raw and Vti. Vti rose 2-3-fold in comparison with Raw. To increase left atrial pressure, a balloon catheter was inserted into the left atrium of the heart and inflated with different volumes. The responses of EL, RL, Raw and Vti were comparable to those with acute fluid load. Alterations in pulmonary mechanics were closely correlated to mean pulmonary artery blood pressure. In another six animals the effect of vagotomy on vascular engorgement was studied. Vagotomy did not alter baseline airway or tissue mechanics. Furthermore, vagotomy did not influence the change of pulmonary mechanics to fluid load or increase of left atrial pressure. Our data indicate that in young piglets vascular engorgement causes alterations in airway and lung tissue mechanics that are not dependent on vagal influences.

Relaxin counteracts asthma-like reaction induced by inhaled antigen in sensitized guinea pigs

In previous studies, the peptide hormone relaxin (RLX) was found to inhibit mast cell secretion and platelet activation. It has been established that the release of mediators from these cells plays a central pathogenic role in allergic asthma. This prompted us to ascertain whether RLX may counteract the respiratory and histopathological abnormalities of the asthma-like reaction to inhaled antigen in sensitized guinea pigs. Guinea pigs were sensitized with ovalbumin and challenged with the same antigen given by aerosol. Some animals received RLX (30 microg/kg BW, twice daily for 4 days) before antigen challenge. Other animals received inactivated RLX in place of authentic RLX. Respiratory abnormalities, such as cough and dyspnea, were analyzed as were light and electron microscopic features of lung specimens. RLX was shown to reduce the severity of respiratory abnormalities, as well as histological alterations, mast cell degranulation, and leukocyte infiltration in sensitized guinea pigs exposed to ovalbumin aerosol. RLX was also found to promote dilation of alveolar blood capillaries and to reduce the thickness of the air-blood barrier. This study provides evidence for an antiasthmatic property of RLX and raises the possibility of new therapeutic strategies for allergic asthma in humans.

Airway wall dimensions during carbachol-induced bronchoconstriction in rabbits

Airway wall area is an important determinant of airway narrowing. We hypothesized that in cross-sectioned peripheral airways, the wall area internal to the outer smooth muscle border (inner wall area) would decrease and the airway wall area external to the outer smooth muscle layer (adventitial area) would increase during bronchoconstriction because of the relocation of blood and/or fluid between these compartments. To test this hypothesis, we used anesthetized open-chest rabbits and measured airway wall dimensions and smooth muscle shortening of membranous airways after carbachol-induced bronchoconstriction using morphometric techniques. Acute (3-min) and sustained (40-min) bronchoconstriction was induced by aerosol nebulization of carbachol and compared with saline treatment. After physiological measurements, the heart base was snared, and the lung and heart were excised en bloc and frozen by using liquid nitrogen while a transpulmonary pressure of 2 cmH2O was maintained. The lung was processed for light-microscopic examination by using a freeze substitution technique. Results show that adventitial area was significantly decreased after sustained but not acute bronchonconstriction. The mechanism of this change, which contradicts our hypothesis, is unclear. However, the decrease of adventitial area could increase rather than decrease the effect of lung parenchymal tethering and attenuate airway narrowing.

Effect of inhaled norepinephrine on the nitroglycerin-induced bronchodilatation in asthmatics

Previous studies on the bronchodilating effect of nitrates yielded conflicting results. We hypothesized that the concomitant bronchial vasodilatation induced by nitrates may limit the increase of airway patency due to bronchial smooth muscle relaxation. To test this hypothesis, we evaluated the bronchodilating effect of nebulized nitroglycerine (NTG), 0.2 mg, in 12 patients with reversible airway obstruction (FEV1 64.3 +/- 8.2% predicted, > 15% increase after salbutamol 200 micrograms by metered-dose inhaler), pretreated with aerosolized norepinephrine (NE) (0.04 mg) or placebo (PL), in a randomized double-blind crossover design, in two separate days. Baseline FEV1 values of the two test days and FEV1 after NE or PL inhalations were not significantly different. After NTG inhalation, FEV1 was 73.8 +/- 7.9% predicted, with NE pretreatment, and 70 +/- 8.2% predicted with PL pretreatment (p < 0.01). The maximal percent increases of FEV1 above baseline were 14.9 +/- 4.8% and 9.2 +/- 2.4%, respectively, after NE and PL pretreatment (p < 0.01). In conclusion, NTG produces a better bronchodilatation when the concomitant vasodilatation is attenuated by a vasocostrictive agent.

Small airways dimensions in asthma and in chronic obstructive pulmonary disease

The purpose of this study was to compare the dimensions of the peripheral airways in fatal asthma with those from patients with nonfatal asthma, mild COPD, and normal lung function. Lung specimens from eight individuals who had fatal asthmatic attacks were obtained at postmortem and compared with similar specimens from three asthmatic patients who died of an unrelated cause and four specimens obtained from known asthmatic patients who required lung resection for tumor. These 15 asthmatic lungs were also compared with lungs resected for peripheral neoplasms from 15 patients with normal airway function (FEV1, % of predicted > 85) and 15 patients with mild chronic airflow obstruction (FEV1, % of predicted < 85). All membranous airways with a long-short diameter ratio of 3:1 or less were examined. The smooth muscle and the tissue areas external and internal to the muscle layer were traced using a Bioquant BQ System 4. The same system was used to evaluate the fraction of the submucosa and adventitia taken up by blood vessels. The adventitial, submucosal, and muscle area of the asthmatic airways were greater than those of COPD and control (p < 0.01), and the muscle area was greater in COPD than in control lungs (p < 0.05). These parameters were also greater in the 8 patients with fatal asthma compared with the 7 patients with nonfatal asthma (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Intravascular volume loading reversibly decreases airway cross-sectional area

High-resolution computed tomography was used to directly determine the short-term effects of intravascular volume expansion on airway caliber. The change in airway cross-sectional area caused by intravascular volume expansion (30 ml/kg, Ringer's lactate) was studied in six anesthetized mini-pigs within 5 min. Twenty-five of 27 large airways (diameter, 2.01 to 5.0 mm) demonstrated decreased internal cross-sectional area (10.56 +/- 1.26 vs 8.66 +/- 1.03 mm2, p < 0.001). Twenty of 24 small airways (diameter, 0.75 to 2.0 mm) showed decreased internal cross-sectional area (1.82 +/- 0.16 vs 1.44 +/- 0.16 mm2, p < 0.001). These changes were rapidly (< 6 min) reversed by intravascular volume reduction. The external airway cross-sectional area did not change. These data suggest rapid, reversible bronchial mucosal vascular engorgement as a cause of increased airway resistance in heart failure.

Effect of airway blood flow on airflow

Resistance to gas flow of an airway is a function of both airway smooth muscle tone and thickness of the airway wall internal to the outer ring of airway smooth muscle. Schematically, the increase in airway resistance caused by shortening of airway smooth muscle may be potentiated by a concomitant increase in airway wall thickness caused by vasodilation of the bronchial vessels and/or microvascular leakage. Conversely, bronchial vasoconstriction may limit to some extent the increase in resistance to gas flow caused by airway smooth muscle shortening and/or congestion and edema of the airway wall. Many endogenous paracrine mediators, putatively involved in asthma and bronchial hyperresponsiveness, have both bronchomotor and vascular effects. The overall effects on resistance to airflow of endogenous or exogenous agents depend not only upon pre-existing airway smooth muscle tone and pre-existing condition of bronchial vessels but also upon two factors that facilitate microvascular leakage, namely, inflammation of the airway wall and outflow pressure of the bronchial circulation, which is close to left atrial pressure.

The airway microvasculature and exercise induced asthma

It has been proposed that exercise induced asthma is a result of "rapid expansion of the blood volume of peribronchial plexi" (McFadden ER, Lancet 1990;335:880-3). This hypothesis proposes that the development of exercise induced asthma depends on the thermal gradient in the airways at the end of hyperpnoea. The events that result in exercise induced asthma are vasoconstriction and airway cooling followed by reactive hyperaemia. We agree that the airway microcirculation has the potential for contributing to the pathophysiology of exercise induced asthma. We do, however, question whether reactive hyperaemia, in response to airway cooling, is the mechanism whereby hyperpnoea provokes airways obstruction in asthmatic patients. Further, we question whether vasoconstriction accompanies dry air breathing and whether an abnormal temperature gradient and rapid rewarming of the airways are prerequisites for exercise induced asthma. From published experiments we conclude that dry air breathing is associated with vasodilation and increase in airway blood flow rather than vasoconstriction and a decrease in blood flow to the airways. We propose that the stimulus for the increase in airway blood flow is an increase in osmolarity of the airway submucosa. This osmotic change is caused by the movement of water to the airway lumen in response to evaporative water loss during hyperpnoea. The increase in airway blood flow may occur directly or indirectly by the osmotic release of mediators. Exercise induced asthma is most likely to be due to the contraction of bronchial smooth muscle caused by the same mediators. Whether it is enhanced or inhibited by alterations in airway blood flow is not yet established in man.

Benefits of caffeine ingestion on sprint performance in trained and untrained swimmers

The influence of specific training on benefits from caffeine (Caf) ingestion was examined during a sprint test in a group of highly trained swimmers (T) and compared with the response of a group of untrained occasional swimmers (UT). Seven T and seven UT subjects swam freestyle two randomly assigned 2 x 100 m distances, at maximal speed and separated by 20 min of passive recovery, once after Caf (250 mg) and once after placebo (Pla) ingestion. Anaerobic capacity was assessed by the mean velocity (meters per second) during each 100 m and blood was sampled from the fingertip just before and 1, 3, 5, 7, and 9 min after each 100 m for resting and maximal blood lactate concentration ([la-]b,max) determination. The [la-]bmax was significantly enhanced by Caf in both T and UT subjects (P less than 0.01). However, only T subjects exhibited significant improvement in their swimming velocity (P less than 0.01) after Caf or any significant impairment during the second 100 m. In light of these results, it appears that specific training is necessary to benefit from the metabolic adaptations induced by Caf during supramaximal exercise requiring a high anaerobic capacity.

Airway blood flow modifies allergic airway smooth muscle contraction

We tested the hypothesis that airway perfusion modifies the contractile response of airway smooth muscle to allergen challenge by influencing the clearance of locally released spasmogens. In six intact, lightly sedated, sheep allergic to Ascaris suum, we measured tracheal mucosal blood flow (Qtr) with a soluble gas uptake method and tracheal dead space (Vtr), an index of airway smooth muscle tone, by helium dilution before and serially after local aerosol challenge with A. suum extract or ragweed extract (control). The former challenge was repeated during continuous intravenous infusion of either vasopressin or nitroglycerin, which by themselves had no effect on Vtr and decreased and increased Qtr, respectively. Ragweed had no effect on Qtr and Vtr, whereas A. suum increased mean (+/- SE) Qtr by 111 +/- 31% (p less than 0.05) and decreased mean Vtr by 15 +/- 2% (p less than 0.05) immediately after challenge, with Qtr returning to baseline by 40 min and Vtr by 80 min. Vasopressin infusion prevented the A. suum-induced increase in Qtr and prolonged the decrease in mean Vtr (p less than 0.05). During nitroglycerin infusion, A. suum failed to alter Qtr or Vtr. Vasopressin and nitroglycerin had no effect on the contractile responses of tracheal smooth muscle to A. suum in vitro. These results indicate that the effects of vasopressin and nitroglycerin on antigen-induced airway smooth muscle contraction in vivo were due to alterations in airway blood flow rather than to alterations in the release of or airway smooth muscle responsiveness to chemical mediators.