Bronchial diseases and lung aeration in children

Bronchial diseases are common in children, and are usually associated with disturbances of aeration. This article briefly summarizes the embryological development and respiratory physiology pertinent to pediatric bronchial diseases. Current diagnostic imaging tools are discussed, with an emphasis on CT, which can demonstrate bronchial pathology such as bronchial obstruction and bronchiectasis in larger bronchi, as well as indirectly show the peripheral physiologic consequences of bronchial disease, such as alterations in aeration. Computed tomography measurements of lung attenuation may aid in diagnosis in problematic cases. Diseases that affect the pediatric airways at different ages are reviewed. Knowledge of these entities is important for accurate interpretation of imaging studies.

[Bronchopulmonary disease in drug abusers]

Drug abuse is a growing problem in industrialized countries, opening the way to new diseases of the respiratory tract. It has been demonstrated that regular inhalation of cannabis has the same consequences as tobacco smoking. The same cannot be said for other drugs. Cocaine, amphetamines or crack expose the patient to particular toxic effects: in addition to barotrauma related to the administration route, syndromes of acute respiratory distress have been described. These result either from bronchial reactions, asthma exacerbation or eosinophil bronchopneumonia, or alveolar involvement: intra-alveolar bleeding, pulmonary edema or organized pneumonia. Respiratory complications induced by opiates, often used in injections, are related to central alveolar hypoventilation and/or the development of injury from pulmonary edema or pneumonia. The pathophysiology of these lesions is not perfectly understood. Besides these specific conditions, infection is a major problem in drug abusers, irrespective of the drug: bacterial pneumonia, tuberculosis, HIV infection are much more frequent in this high-risk group. Finally repeated intravenous injections of various drugs designed for oral intake can lead to severe complications such as pulmonary hypertension or toxic interstitial lung disease. Summarizing, respiratory diseases in drug abuses can take on a wide range of quite complex presentations. Occasional or regular use of illicit drugs can lead, not exceptionally, to severe respiratory complications requiring rapid management. Knowledge of the principal complications and the appropriate diagnostic procedures is indispensable.

External-beam radiation therapy in the treatment of diffuse tracheobronchial amyloidosis

Tracheobronchial amyloidosis is characterized by deposits of amyloid in airway walls. No effective treatment is known. We describe a 59-year-old woman who presented with increasing symptoms of airway obstruction due to diffuse deposition of amyloid throughout her tracheobronchial tree. She was treated with external-beam radiation therapy (20 Gy) with marked improvement in her symptoms, effort tolerance, bronchoscopic appearance, and forced expiratory volume in 1 second (1.39 L to 1.97 L [42%]). This improvement was maintained during 21 months of follow-up.

[Tracheobronchopathia osteochondroplastica]

OBJECTIVE

To describe the clinical manifestations of tracheobronchopathia osteochondroplastica (TO).

METHODS

X-ray film, CT-scanning, lung function, fibro-bronchoscopy and histological examination were performed in all 4 patients. Clinical features were analyzed with reviewing the reported literatures.

RESULTS

From June 1999 to May 2000, 4 cases of TO (male/female: 2/2, age: 35 approximately 60 yrs) were found among the 1 125 cases of fibro-bronchoscopy, with the positive rate of 0.35%. TO was characterized by cartilaginous and /or osseous submucosal nodules in the trachea and the central bronchi. Symptoms included cough (3/4), hemoptysis (2/4), hoarseness (1/4), with one case of entirely symptom free. Radiography showed no use for the diagnosis. Multiple submucosal nodules and plaques that outgrew into the lumen of the trachea were revealed by CT-scanning in 3 of 4 cases. Pulmonary function testing showed normal in 3 patients and mild obstruction in 1 patient. The bronchoscopic appearance of TO presented with multiple whitish, hard nodules projecting into the tracheal lumen from anterior and lateral walls, with sparing of the posterior wall. Pathological examination showed island of bony tissue and cartilage in the submucosa with almost intact respiratory epithelium. The symptoms and mucosal hyperemia were improved in one patient treated with beclomethasone dipropionate and theophylline for 6 months.

CONCLUSIONS

As an uncommon disease, TO is often misdiagnosed or underdiagnosed. Fibro-bronchoscopy and CT scan remain the main methods for the diagnosis of TO.

Fiberoptic bronchoscopic balloon dilatation in malignant tracheobronchial disease: indications and results

STUDY OBJECTIVES

Bronchoscopic balloon dilatation (BBD) has become a valuable tool in the treatment of benign tracheobronchial stenoses. The objective of this study was to assess indications for and results of fiberoptic BBD in treating malignant lesions.

DESIGN

One hundred twenty-six balloon dilatation procedures were performed in 78 patients with predominantly bronchial carcinoma. BBD was only performed when alternative modes of local treatment (eg, laser therapy or stent implantation) were not indicated or were inappropriate. Indications were symptomatic stenoses of the tracheobronchial tree: dyspnea or stridor (52%), retention pneumonia (15%), atelectasis (10%), retention of secretions (21%), or lung abscess (2%).

RESULTS

Fifty-five percent of all procedures consisted of dilatations of tracheal or bronchial lesions (group 1). In 22% of procedures, a stent was dilated (group 2). In 13%, BBD was used to facilitate stent placement (group 3), and in 10% to enable the correct positioning of irradiation probes for brachytherapy (group 4). In group 1 and group 2, 2 of 2 lung abscesses resolved, 5 of 8 atelectases resolved, and 11 of 12 retention pneumonias resolved. Dyspnea improved in only 12 of 32 patients. No abscess recurred. Two pneumonias and two atelectases reappeared due to restenosis. Stent implantation and brachytherapy procedures were facilitated in 90% of cases. In 52% of cases, BBD was supported by high-frequency jet ventilation. Complications consisted of one fatal hemoptysis caused by a lacerated pulmonary artery, and minor bleeding not necessitating specific therapy.

CONCLUSIONS

Fiberoptic BBD is useful in the management of airway stents prior to and postimplantation, as well as in the placement of brachytherapy catheters. BBD is also successful in the resolution of poststenotic lung abscesses, retention pneumonias, and atelectases.

Immediate allergic response in small airways

The role of small airways in the immediate allergic response is largely unknown. We therefore used the model of precision-cut lung slices (PCLS) in combination with quantitative videomicroscopy to study the early allergic response to allergen in airways ranging from 50 to 900 microm. After PCLS from untreated Wistar rats had been passively sensitized for 16 h with serum from sensitized Brown Norway rats, exposure to 0.1% ovalbumin resulted in an immediate allergic response. Both extent (r = 0.74, p < 0.0001) and velocity (r = 0.49, p < 0.0001) of the allergen-induced bronchoconstriction increased with decreasing airway size. In addition, we observed that smaller airways not only contracted stronger and quicker, but that they also relaxed faster, suggesting that smaller airways are more reactive in principle. The allergen-induced bronchoconstriction in PCLS was prevented by the serotonin receptor antagonist ketanserin (IC(50) 6 nM), but not by antagonists directed against histamine, acetylcholine, PAF, or endothelin receptors, or by cyclooxygenase or lipoxygenase inhibitors. Like allergen, serotonin provoked responses that were stronger in smaller airways. These findings suggest that the immediate allergic response in rat PCLS depends largely on serotonin and that this response can occur in nearly all airway generations, but is most pronounced in the smallest airways, that is, the terminal bronchioles.

IL-5-induced airway eosinophilia--the key to asthma?

Bronchial asthma is a chronic inflammatory airway disease defined by reversible airway obstruction and non-specific airway hyper-responsiveness (AHR). Although profound insights have been made into the pathophysiology of asthma, the exact mechanisms inducing and regulating the disease are still not fully understood. Yet, it is generally accepted that the pathological changes in asthma are induced by a chronic inflammatory process which is characterized by infiltration of the bronchial mucosa with lymphocytes and eosinophils, increased mucus production and submucosal edema. There is increasing evidence that an imbalance in the T-helper (Th) cell response of genetically predisposed individuals to common environmental antigens plays a pivotal role in the pathogenesis of allergic bronchial asthma and other atopic disorders. Following allergic sensitization, T cells from atopic patients tend to produce elevated levels of Th2-type cytokines, especially interleukin (IL)-4, IL-13, IL-5 and IL-6, which induce and regulate IgE production and eosinophil airway infiltration. In this review, the role of Th2-type cytokines, IgE and airway eosinophils in the induction of airway inflammation and AHR is discussed, and animal studies of asthma and AHR, mainly in rodents will be considered. A better understanding of the underlying mechanisms leading to asthma pathology may yield more specific immunological strategies for the treatment of this disease which is increasing worldwide.

[The role of bronchospasm in the impaired bronchial permeability in sarcoidosis]

VC, FVC, FEV1, FEV1/VC%, PEF, MEF25, MEF50, MEF75 were registered in 24 sarcoidosis patients before and after inhalation of 1 dose of berotec and 1 dose of atrovent. Bronchospasm took place in 20.8% patients. Bronchospasm was the only cause of bronchial obstruction in 16.7%, one of the causes in 4.2%. Contribution of bronchospasm to development of bronchial obstruction was essential in all the examinees (91-100%).

Aspergillus and endobronchial abnormalities in lung transplant recipients

STUDY OBJECTIVE

To determine the relationship between aspergillus recovery from the airways of lung transplant recipients and the development of endobronchial abnormalities.

DESIGN

Retrospective case series.

SETTING

Tertiary-care hospital.

PATIENTS

All patients who underwent lung transplantation between December 1991 and June 1999.

MEASUREMENTS AND RESULTS

The study cohort included 38 patients. The primary end point was the bronchoscopic identification of an endobronchial abnormality. Aspergillus was isolated from the lungs of nine patients (23.7%). Most of these isolates occurred early after transplantation (mean, 8 weeks). Endobronchial abnormalities arose in seven of the patients (18.4%) and manifested as either exuberant granulation tissue or stricture formation. Six of the 9 (66.6%) patients with aspergillus developed airway lesions, compared to 1 of the 29 patients (3.4%) without aspergillus (p = 0.0002). Endobronchial abnormalities were 19.3 times more likely to occur in patients in whom aspergillus had previously been isolated. As a screening test for the subsequent diagnosis of an airway complication, the recovery of aspergillus had a sensitivity and specificity of 85.7% and 90.3%, respectively. These aspergillus-related endobronchial abnormalities were clinically relevant as evidenced by a mean increase of 25.9% in the FEV(1) after bronchoscopic intervention.

CONCLUSION

The early isolation of aspergillus from the airways of lung transplant recipients identifies patients at increased risk for the development of clinically significant endobronchial abnormalities.

Reproducibility of bronchodilator response for a reservoir dry powder inhaler following routine clinical use

The performance of dry powder inhaler (DPI) devices, particularly reservoir DPIs, may be influenced by environmental conditions. This study compared the bronchodilator efficacy and in vitro aerosol characteristics of salbutamol, delivered via a novel reservoir DPI (Clickhaler) and a conventional pressurized metered-dose inhaler (MDI) before and after use of the DPI in clinical practice. Following a screening visit, patients received cumulative doses of salbutamol (100, 200, and 400 microg) via DPI or MDI on separate days in a double-blind, crossover design before and after a 4-week period, during which the DPI was used as the patients' first-line bronchodilator. Lung function responses (forced expiratory volume in 1 sec [FEV1], forced vital capacity [FVC], and peak expiratory flow [PEF]) to salbutamol delivered by DPI and MDI and in vitro aerosol characteristics were not significantly different before and after the period of DPI patient use. DPI performance, assessed in vivo and in vitro, is maintained following an extended period of patient use.

Small airways obstruction syndrome

STUDY OBJECTIVES

To clarify the significance of a functional lung pattern characterized by a decreased vital capacity (VC) and an increased residual volume (RV), but with a normal FEV1/VC ratio.

SETTING

A university teaching hospital.

SUBJECTS

Patients with bronchial asthma, pulmonary emphysema, and small airways disease, and older subjects.

MEASUREMENTS

Measurements of static and dynamic lung volumes, diffusing capacity of the lung for carbon monoxide (as measured by the single-breath method), nitrogen slope of the alveolar plateau, and closing volume (as measured by the single-breath O2 test).

CONCLUSION

A functional pattern characterized by a decreased VC and FEV1 and increased RV, but with a normal FEV1/VC ratio and total lung capacity, reflects an obstructive impairment of small airways.

Bronchial mucormycosis with progressive air trapping

A previously healthy 70-year-old woman developed fever, cough, and exertional dyspnea. Her symptoms progressed over a 2-month period despite treatment by her primary care physician with 2 courses of oral antibiotics and the addition of prednisone. Hypoxemia and the finding of hyperglycemia with mild ketoacidosis led to hospital admission. Serial chest radiographs demonstrated diffuse heterogeneous pulmonary opacities and progressive air trapping in the right lower lobe. Fiberoptic bronchoscopy revealed a deep penetrating ulcer with exposed bronchial cartilage of the bronchus intermedius and dynamic airway obstruction with complete closure during expiration. Biopsy of the ulcer revealed Rhizopus arrhizus. Respiratory failure stabilized with the patient on conventional mechanical ventilation and receiving amphotericin B. Before surgery could be performed, Pseudomonas aeruginosa pneumonia and septic shock developed, and the patient died.

Tracheobronchial malacia and stenosis in children in intensive care: bronchograms help to predict oucome

BACKGROUND

Severe tracheobronchial malacia and stenosis are important causes of morbidity and mortality in children in intensive care, but little is known about how best to diagnose these conditions or determine their prognosis.

METHODS

The records of all 62 children in whom one or both of these conditions had been diagnosed by contrast cinetracheobronchography in our intensive care unit in the period 1986-95 were studied.

RESULTS

Seventy four per cent of the 62 children had congenital heart disease; none was a preterm baby with airways disease associated with prolonged ventilation. Fifteen of the children had airway stenosis without malacia; three died because of the stenosis and two died from other causes. Twenty eight of the 47 children with malacia died; only eight children survived without developmental or respiratory handicap. All children needing ventilation for malacia for longer than 14 consecutive days died if their bronchogram showed moderate or severe malacia of either main bronchus (15 cases), or malacia of any severity of both bronchi (three additional cases); all children needing ventilation for malacia for longer than 21 consecutive days died if their bronchogram showed malacia of any severity of the trachea or a main bronchus (three additional cases). These findings were strongly associated with a fatal outcome (p<0.00005); they were present in 21 children (all of whom died) and absent in 26 (of whom seven died, six from non-respiratory causes). They had a positive predictive value for death of 100%, but the lower limit of the 95% confidence interval was 83.9% so up to 16% of patients meeting the criteria might survive.

CONCLUSION

In this series the findings on contrast cinetracheobronchography combined with the duration of ventilation provided a useful guide to the prognosis of children with tracheobronchomalacia. The information provided by bronchoscopy was less useful.

Pulmonary function improves after expandable metal stent placement for benign airway obstruction

STUDY OBJECTIVE

To determine whether expandable metal stent placement for benign airway lesions improves pulmonary function.

DESIGN

Case series.

SETTING

University medical center.

PATIENTS

Nine patients who underwent balloon-mediated expandable metal stent deployment for airway obstruction due to benign etiologies.

RESULTS

All nine patients had expandable stents deployed for benign airway lesions using fiberoptic bronchoscopy and fluoroscopic guidance. Pulmonary function improved after stent placement. The mean FVC increased by 388 mL (95% confidence interval [CI], 30 to 740 mL), the mean peak expiratory flow (PEF) increased by 1,288 mL (95% CI, 730 to 1,840 mL), the mean FEV1 increased by 550 mL (95% CI, 240 to 860 mL), and the mean forced expiratory flow between 25% and 50% of vital capacity (FEF25-75%) increased by 600 mL (95% CI, 110 to 1,090 mL). Corresponding relative measurements included increases in FVC (12%), PEF (95%), FEV1 (38%), and FEF25-75% (87%). The complete characterization of a benign airway obstruction generally required a multimodal approach.

CONCLUSIONS

Expandable metal stent placement appears to be an effective therapy for benign airway obstruction.

Lung involvement in primary Sjögren's syndrome is mainly related to the small airway disease

OBJECTIVE

To evaluate lung involvement in patients with primary Sjögren's syndrome.

METHODS

Sixty one consecutive, non-smoking patients, 58 women and three men, were evaluated clinically, physiologically, and radiologically. A bronchial and/or transbronchial biopsy was performed on 13 of the patients. Physiological data were compared with that of a control group of 53 healthy non-smoking subjects matched for age and sex.

RESULTS

In 41% of the patients the main symptom was dry cough. Physiological studies revealed that the patients presented significantly lower expiratory flow values (% pred) when compared with those of the control group: the forced expiratory volume in one second (FEV1) (mean (SD)) was 96% (16) v 111% (13) (p < 0.0001), the maximal expiratory flow at the 50% of the vital capacity (MEF50) was 72% (24) v 103% (17) (p < 0.0001), and the maximal expiratory flow at the 25% of the vital capacity (MEF25) was 49% (25) v 98% (20) (p < 0.0001). No significant difference was noted for the carbon monoxide diffusion value (% pred), between patients and controls. Blood gases were evaluated in 44 patients: mild hypoxemia was observed, and the alveolo-arterial oxygen difference (P(A-a)O2) correlated significantly with MEF50 (r = 0.35, p < 0.01) and MEF25 (r = 0.33, p < 0.01) values. Chest radiography showed mild, interstitial-like changes in 27 patients while slightly increased markings were present in 21. High resolution computed tomography of the lungs was performed in 32 patients (four with a normal chest radiograph, six with suspected interstitial pattern, 19 with apparent interstitial pattern, and three with hyperinflation) and revealed predominantly wall thickening at the segmental bronchi. All positive findings by computed tomography derived from the patients with abnormal chest radiographs. Transbronchial and/or endobronchial biopsy specimens in 10 of the 11 sufficient tissue samples revealed peribronchial and/or peribronchiolar mononuclear inflammation, while interstitial inflammation coexisted in two patients.

CONCLUSION

The airway epithelia seem to be the main target of the inflammatory lesion of the lung in patients with primary Sjögren's syndrome. It seems to be common, subclinically leading to obstructive small airway physiological abnormalities.

Use of balloon-expandable metallic stents in the management of bronchial stenosis and bronchomalacia after lung transplantation

STUDY OBJECTIVES

Bronchial stenosis (BS) and bronchomalacia (BM) are often associated with lung allograft rejection or infection in lung transplant (LT) recipients. We reviewed our experience using balloon-expandable metallic (Palmaz) stents in the management of BS and BM in LT.

DESIGN

Retrospective review of cases.

PATIENTS

LT recipients with bronchoscopic and spirometric evidence of BS and BM.

INTERVENTIONS

Serial balloon dilation was performed for BS. Stent placement was done for refractory or recurrent BS, or persistent focal BM.

RESULTS

Twelve of 129 LT bronchial anastomoses at risk (9.3%) had complications, which included 11 BS and 5 BM. Four BS were accompanied by BM either concurrently or subsequently. The only isolated BM was associated with acute rejection and resolved after appropriate medical therapy. Balloon dilations alone were successful in relieving BS in three cases. Seven patients received a total of 11 stents. Stents were placed under conscious sedation using a flexible bronchoscope. Five of the seven patients had spirometric improvements after stent placements. One patient had no spirometric improvement, and another died before a follow-up study was done. There were no complications during stent placements. However, complications after stent placements included partial dehiscence of the stent from the bronchial wall, stent migration, partial obstruction of a segmental bronchial orifice by a stent in the main bronchus, and longitudinal stent collapse. One stent was successfully removed using a flexible bronchoscope in the endoscopy suite, and two others were removed by rigid bronchoscopy in the operating room.

CONCLUSIONS

Endobronchial placement of the Palmaz stent in LT recipients is relatively easy, and it can be removed if needed. However, because there are significant potential complications, the future use of this stent as an airway prosthesis in LT remains unclear.

Pseudophysiologic emphysema resulting from severe small-airways disease

Loss of lung elastic recoil causing hyperinflation with increased TLC and decreased diffusing capacity and expiratory airflow are physiologic hallmarks of emphysema. We studied lung mechanics in 10 patients (seven men and three women) aged 69 +/- 9 yr (mean +/- SD) who had fixed, severe expiratory airflow limitation with a mean FEV1 = 0.73 +/- 0.1 L (mean +/- SD) (32 +/- 7% predicted) and lung computed tomographic picture grade score <= 20, indicating no or trivial emphysema. Three patients died, in whom whole-lung emphysema scores were 15 each and small airways were abnormal. Marked hyperinflation was present in all 10 patients studied, with TLC 7.3 +/- 1.1 L (140 +/- 12% predicted); FRC 5.6 +/- 0.8 L (177 +/- 30% predicted); and RV 5.2 +/- 0.8 L (242 +/- 28% predicted). Diffusing capacity of carbon monoxide (DLCO was reduced, at 12 +/- 6 ml/min/mm Hg (61 +/- 29% predicted). The pressure-volume curves of the lung were markedly abnormal. Pst(L) at TLC was 11.6 +/- 1.4 cm H2O. Transdiaphragmatic pressure (Pdi) in five patients was 66 +/- 13 cm H2O. These results indicate that severe small-airways disease with no or trivial emphysema may cause a spurious reduction in diffusing capacity as well as severe loss of lung elastic recoil resulting in marked hyperinflation, increased TLC, and decreased Pdi and expiratory airflow.

Pulmonary infection with Mycobacterium avium-intracellulare leads to air trapping distal to the small airways

To clarify the structure and function of the airways in Mycobacterium avium-intracellulare (MAI) infection, we performed pulmonary function tests and high-resolution computed tomography (HRCT) of the thorax in female patients 61 +/- 9 yr of age (n = 12) with pulmonary MAI infection without predisposing lung disease and compared their data with those of normal female volunteers 54 +/- 8 yr of age (n = 9). We calculated the E/I ratio, i.e., the average ratio of HRCT number at full expiration to that at full inspiration, as an index for the evaluation of air trapping distal to the small airways. Patients showed significant increases in residual volume and slope of phase III (DeltaN2) of the single-breath nitrogen test, and significant decreases in flow at 50 and 25% of FVC, suggesting hyperinflation and obstruction of the small airways. HRCT of patients revealed the small nodules and ectasis of bronchioles and small bronchi located mainly in segments (S) S2, S3, S4, and S5. The E/I ratio was significantly elevated in patients, and especially higher in the upper lung field than in the lower lung field, suggesting air trapping distal to the small airways. The difference of E/I ratio between the upper and lower field is probably related to the segmental distribution of CT abnormalities. These findings suggest that MAI infection can lead to air trapping distal to the small airways.

Self-expanding metal stents for the management of bronchial stenosis and bronchomalacia after lung transplantation

BACKGROUND

Airway stenosis or malacia after lung transplantation, usually as a result of anastomotic ischemia, remains a major problem.

METHODS

The authors report their experience with the Gianturco expandable stent for the management of 23 bronchial stenoses in 18 patients following lung transplantation. Stent placement occurred an average of 5.6 months after transplantation.

RESULTS

Stents were well tolerated and produced immediate symptomatic and functional improvement. The mean follow-up after implantation was 21 months (range, 4 to 48 mo). The authors removed five stents by endoscopy and replaced them, and removed one stent entirely. Laser resection was used to control granulomas or partial fibrosis stenosis that occurred in four stents (14.3%) after an average of 4 months. One stent broke but was still in place and effective 32 months later. One patient died of hemorrhage 4 months after stenting.

CONCLUSION

Although it can still be improved, this expandable metal stent is suitable for the treatment of posttransplantation proximal bronchial stenosis.

Diagnostic features and therapeutic outcome of erosive and ulcerous endobronchial tuberculosis

SETTING AND OBJECTIVE

Erosive and ulcerous endobronchial tuberculosis (EBTB) is distinct from pulmonary tuberculosis in some aspects. We evaluated the clinical features of 56 patients (26 males and 30 females) with EBTB to characterize the clinical features of the disease.

RESULTS

The chief complaint in 70% of patients was intractable cough, particularly in those with tracheal tuberculosis. The predominant radiological features were patchy bi-apical infiltrates of variable intensity without cavitation; for six patients, however, plain radiographs revealed no abnormalities. The ulcerous lesions could be classified into three stages: active, healing and scarring. Furthermore, we divided scarring stage into two subtypes, polypoid and non-polypoid. Most of the patients were treated with isoniazid, rifampin, and streptomycin (SM) or ethambutol. Approximately one-third of the patients, not randomly selected, were treated with aerosolized SM and corticosteroids in addition to conventional oral therapy.

CONCLUSION

EBTB involves typical clinical and radiographic features. In this uncontrolled series, it was our impression that the period of time to healing of ulcerous lesions seemed to be shorter in those treated with aerosol therapy including streptomycin and corticosteroids.

Exhaled nitric oxide (NO) is reduced shortly after bronchoconstriction to direct and indirect stimuli in asthma

Exhaled NO is increased in patients with asthma and may reflect disease severity. We examined whether the level of exhaled NO is related to the degree of airway obstruction induced by direct and indirect stimuli in asthma. Therefore, we measured exhaled NO levels before and during recovery from histamine and hypertonic saline (HS) challenge (Protocol 1) or histamine, adenosine 5'-monophosphate (AMP), and isotonic saline (IS) challenge (Protocol 2) in 11 and in nine patients with mild to moderate asthma, respectively. The challenges were randomized with a 2-d interval. Exhaled NO and FEV1 were measured before and at 4, 10, 20, and 30 min after each challenge. NO was measured during a slow VC maneuver with a constant expiratory flow of (0.05 x FVC)/s against a resistance of 1 to 2 cm H2O. Baseline exhaled NO levels were not significantly different between study days in Protocol 1 (mean +/- SD: 4.8 +/- 1.8 ppb [histamine] versus 5.4 +/- 2.1 ppb [HS], p = 0.4) or in Protocol 2 (7.9 +/- 4.7 ppb [histamine], 8.3 +/- 5.2 ppb [AMP], and 7.2 +/- 3.7 ppb [IS], p = 0.7). A significant reduction in exhaled NO was observed directly after HS (mean +/- SEM: 39.2 +/- 3.9 %fall) and AMP challenge (32.3 +/- 7.3 %fall) (MANOVA, p < 0.001), respectively, whereas exhaled NO levels tended to decrease after histamine challenge. Isotonic saline challenge did not induce changes in exhaled NO (p = 0.7). There was a positive correlation between %fall in FEV1 and the %fall in exhaled NO after histamine, HS, and AMP challenge as indicated by the mean slope of the within-subject regression lines (p <= 0.04). We conclude that acute bronchoconstriction, as induced by direct and indirect stimuli, is associated with a reduction in exhaled NO levels in asthmatic subjects. This suggests that airway caliber should be taken into account when monitoring exhaled NO in asthma.