Usefulness of exhaled nitric oxide to guide risk stratification for bronchiolitis obliterans syndrome after lung transplantation

An official JRS statement: The principles of fractional exhaled nitric oxide (FeNO) measurement and interpretation of the results in clinical practice

Nitric oxide (NO) is produced in the body and has been shown to have diverse actions in the abundance of research that has been performed on it since the 1970s, leading to Furchgott, Murad, and Ignarro receiving the Nobel Prize in Physiology or Medicine in 1998. NO is produced by nitric oxide synthase (NOS). NOS is broadly distributed, being found in the nerves, blood vessels, airway epithelium, and inflammatory cells. In asthma, inflammatory cytokines induce NOS activity in the airway epithelium and inflammatory cells, producing large amounts of NO. Measurement of fractional exhaled nitric oxide (FeNO) is a simple, safe, and quantitative method of assessing airway inflammation. The FeNO measurement method has been standardized and, in recent years, this noninvasive test has been broadly used to support the diagnosis of asthma, monitor airway inflammation, and detect asthma overlap in chronic obstructive pulmonary disease (COPD) patients. Since the normal upper limit of FeNO for healthy Japanese adults is 37 ppb, values of 35 ppb or more are likely to be interpreted as a signature of inflammatory condition presenting features with asthma, and this value is used in clinical practice. Research is also underway for clinical application of these measurements in other respiratory diseases such as COPD and interstitial lung disease. Currently, there remains some confusion regarding the significance of these measurements and the interpretation of the results. This statement is designed to provide a simple explanation including the principles of FeNO measurements, the measurement methods, and the interpretation of the measurement results.

Combined diffusing capacity for nitric oxide and carbon monoxide as predictor of bronchiolitis obliterans syndrome following lung transplantation

BACKGROUND

There is a need for non-invasive parameters that are sensitive to the development of the bronchiolitis obliterans syndrome (BOS) in lung transplantation (LTx) patients. We studied whether the pulmonary diffusing capacity for inhaled nitric oxide is capable of detecting BOS stages.

METHODS

Sixty-one LTx patients were included into this cross-sectional study (19/29/7/3/3 in BOS stages 0/0-p/1/2/3). For analysis stages 0/0-p versus 1/2/3 ("BOS binary-early"), and stages 0/0-p/1 versus 2/3 ("BOS binary-late") were summarized. Measurements of the combined diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO) were compared with spirometry and bodyplethysmography, and their relative importance was evaluated by discriminant analysis.

RESULTS

Regarding the recognition of "BOS binary-early", among spirometric parameters forced expiratory volume in 1 s (FEV1) was best, among bodyplethysmographic parameters airway resistance, and among diffusing parameters DLNO. Regarding "BOS binary-late", DLNO was inferior to bodyplethysmographic parameters.

CONCLUSION

Although the study comprised only measurements at a single time point and no follow-up, DLNO outperformed FEV1, the time course of which is used in detecting BOS. Together with its pathophysiological plausibility, this result suggests that the measurement of DLNO, possibly over time, could be an easily applicable tool for the monitoring of LTx patients and should be evaluated in larger studies.

Persistence of de novo donor specific HLA-Antibodies after lung transplantation: a potential marker of decreased patient survival

The impact of de novo donor-specific anti-HLA antibodies (DSA) on outcomes in lung transplantation is still a matter of debate. We hypothesize that differentiating DSA by persistent and transient appearance may offer an additional risk assessment. The clinical relevance of HLA-antibodies was investigated prospectively in 72 recipients with a median follow-up period of 21 months. The presence of HLA-antibodies was analysed by single antigen bead assay prior to and after (3 weeks, 3, 6, 12 and 18 months) transplantation. In 23 patients (32%) de novo DSA were detected. In 10 of these patients (44%) DSA persisted throughout the follow-up period whereas 13 of these patients (56%) had transient DSA. There was a trend towards lower one-year-survival in DSA positive compared to DSA negative patients (83% versus 94%; p=0.199). Remarkably, patients with persistent DSA had significantly reduced survival (one-year survival 60%) compared with both patients without DSA and those with transient DSA (p=0.005). Persistent DSA represented an independent prognostic factor for reduced overall survival in multivariate analysis (HR 8.3, 95% CI 1.8-37.0; p=0.006). Persistence of DSA during the first year after transplantation seems to be more harmful for lung allograft function than transiently detected DSA at an early stage. This article is protected by copyright. All rights reserved.

Is It Possible to Predict Pulmonary Complications and Mortality in Hematopoietic Stem Cell Transplantation Recipients from Pre-Transplantation Exhaled Nitric Oxide Levels?

OBJECTIVE

Chemo/radiotherapy-induced free oxygen radicals and reactive oxygen derivatives contribute to the development of early and late transplantation-related pulmonary and extra-pulmonary complications in hematopoietic stem cell transplantation (HSCT) recipients. It has been proposed that an increase in fractional exhaled nitric oxide (FeNO) level indicates oxidative stress and inflammation in the airways. The aim of this prospective study is to evaluate the pre-transplantation FeNO levels in HSCT patients and to search for its role in predicting post-transplantation pulmonary complications and mortality.

MATERIALS AND METHODS

HSCT patients were included in the study prospectively between October 2009 and July 2011. Pre-transplantation FeNO levels were measured with a NIOX MINO® device prior to conditioning regimens. All patients were monitored prospectively for post-transplantation pulmonary complications with medical history, physical examination, chest X-ray, and pulmonary function tests.

RESULTS

A total of 56 patients (33 autologous, 23 allogeneic) with mean age of 45±13 years were included in the study, among whom 40 (71%) were male. Pre-transplantation FeNO level of the whole study group was found to be 24±13 (mean ± standard deviation) parts per billion (ppb). The FeNO level in allogeneic HSCT recipients was 19±6 ppb while it was 27±15 ppb in autologous HSCT recipients (p=0.042). No significant correlation was found between the pre-transplantation chemotherapy and radiotherapy protocols and baseline FeNO levels (p>0.05). Post-transplantation pulmonary toxicity was identified in 12 (21%) patients and no significant relationship was found between baseline FeNO levels and pulmonary toxicity. The survival rate of the whole study group for 1 year after transplantation was 70%. No significant relationship was identified between baseline FeNO values and survival (FeNO 19±7 ppb in patients who died and 26±15 ppb in the survivors; p=0.114).

CONCLUSION

Pre-transplantation FeNO measurement does not seem to have a role in predicting post-transplantation pulmonary complications and mortality.

Postinfectious bronchiolitis obliterans in children: lessons from bronchiolitis obliterans after lung transplantation and hematopoietic stem cell transplantation

Postinfectious bronchiolitis obliterans (PIBO) is an irreversible obstructive lung disease characterized by subepithelial inflammation and fibrotic narrowing of the bronchioles after lower respiratory tract infection during childhood, especially early childhood. Although diagnosis of PIBO should be confirmed by histopathology, it is generally based on history and clinical findings. Irreversible airway obstruction is demonstrated by decreased forced expiratory volume in 1 second with an absent bronchodilator response, and by mosaic perfusion, air trapping, and/or bronchiectasis on computed tomography images. However, lung function tests using spirometry are not feasible in young children, and most cases of PIBO develop during early childhood. Further studies focused on obtaining serial measurements of lung function in infants and toddlers with a risk of bronchiolitis obliterans (BO) after lower respiratory tract infection are therefore needed. Although an optimal treatment for PIBO has not been established, corticosteroids have been used to target the inflammatory component. Other treatment modalities for BO after lung transplantation or hematopoietic stem cell transplantation have been studied in clinical trials, and the results can be extrapolated for the treatment of PIBO. Lung transplantation remains the final option for children with PIBO who have progressed to end-stage lung disease.

A Critical Care and Transplantation-Based Approach to Acute Respiratory Failure after Hematopoietic Stem Cell Transplantation in Children

Acute respiratory failure contributes significantly to nonrelapse mortality after allogeneic hematopoietic stem cell transplantation. Although there is a trend of improved survival over time, mortality remains unacceptably high. An understanding of the pathophysiology of early respiratory failure, opportunities for targeted therapy, assessment of the patient at risk, optimal use of noninvasive positive pressure ventilation, strategies to improve alveolar recruitment, appropriate fluid management, care of the patient with chronic lung disease, and importantly, a team approach between critical care and transplantation services may improve outcomes.

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Outcomes from acute respiratory failure after hematopoietic stem cell transplantation remain unacceptably high.

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The review focuses on strategies to improve these outcomes.

Application of nitric oxide measurements in clinical conditions beyond asthma

Fractional exhaled nitric oxide (FeNO) is a convenient, non-invasive method for the assessment of active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid diagnosis and monitoring in several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory, infectious, and/or immunological conditions. In this short review, we provide an overview of several clinical studies and discuss the status of potential applications of NO measurements in clinical conditions beyond asthma.

Bronchiolitis obliterans syndrome due to donor-specific HLA-antibodies

Chronic lung allograft dysfunction (CLAD) is a limiting factor for long-term survival in lung transplant recipients. Donor-specific human leukocyte antigen (HLA)-antibodies (DSA) have been suggested as potential risk factors for CLAD. However, their impact on clinical outcome following lung transplantation remains controversial. We performed a single-center study of 120 lung transplant recipients transplanted between 2006 and 2011. Patient sera were investigated before and after transplantation. The sera were screened by means of Luminex(®) technology (Luminex Inc., Austin, TX, USA) for IgG-HLA-class I and class II antibodies (ab). Using single antigen beads, DSA were identified and correlated retrospectively with clinical parameters. After transplantation 39 out of 120 patients (32.5%) were positive for HLA-ab. The incidence of de novo DSA formation was 27 of 120 patients (22.5%). Eleven of 27 (41%) of de novo DSA-positive patients developed BOS compared to 13 of 93 (14%) DSA-negative patients (p = 0.002). Furthermore, the generation of de novo DSA was independently associated with the development of BOS in multivariable analysis [hazard ration (HR) 2.5, 95% confidence interval (CI) 1.0-6.08; p = 0.046). Our results indicate that de novo DSA are associated with the development of BOS after lung transplantation. Monitoring of HLA-ab after transplantation is useful for identifying high-risk patients and offers an opportunity for early therapeutic intervention.

Airway inflammation in children and adolescents with bronchiolitis obliterans

BACKGROUND

Airway inflammation plays a major role in the progression of chronic lung diseases. The features of airway inflammation are not well defined among patients with cases of bronchiolitis obliterans (BO) that began in childhood.

OBJECTIVES

To investigate the sputum cell and cytokine profiles of stable cases of BO regarding lung function and the involvement of small airway disease (SAD).

METHODS

Twenty patients with BO (median age=14.5, range=7-23years) and 22 healthy controls (median age=16.5years, range=7-24years) were investigated. Lung function parameters and bronchial reversibility testing as well as sputum cell and cytokine profiles (IL-1β, IL-6, IL-8, TNF-α, IL-5, IFN-γ, and NFκB regulation) were analysed using quantitative RT-PCR and cytometric bead assay (CBA) in induced sputum.

RESULTS

Patients with BO had significantly lower lung function values, including FVC, forced expiratory volume (FEV1), the Tiffeneau index (FEV1/VC), and MEF25, but increased functional residual capacity (RV/TLC) values. Bronchial reversibility was found in five patients (25%). Moreover, airway inflammation (as indicated by total cells, neutrophils, IL-1β, IL-6, IL-8, TNF-α, and NFκB) was significantly increased among patients with BO compared with controls.

CONCLUSIONS

BO is predominantly a neutrophilic disease of the small bronchioles featuring elevated levels of pro-inflammatory cytokines leading to tissue remodelling and fibrosis of the small airways. Future therapies for patients with BO should more efficiently target the small airways.

Serial monitoring of exhaled nitric oxide in lung transplant recipients

BACKGROUND

Exhaled nitric oxide (FeNO), a marker of airway inflammation, is often elevated in lung transplant recipients (LTxRs) with acute rejection or infection. Isolated measurements in the setting of bronchiolitis obliterans syndrome have been variable. We sought to assess the utility of serial FeNO in predicting chronic allograft dysfunction or the presence of acute rejection or infection.

METHODS

Eighty-six LTxRs underwent 325 serial FeNO measurements at an expiratory flow rate of 50 ml/s. The change in FeNO (ΔFeNO) between two measurements obtained during a stable state (ΔFeNO-SS) was compared with ΔFeNO, where the first measurement was taken during a stable state and the second during an unstable state (defined as a subsequent decline in FEV1 > 10% over 3 months [ΔFeNO-SU]) or an acute complication (acute rejection, lymphocytic bronchiolitis or acute infection [ΔFeNO-SAC]). The median follow-up time after the baseline FeNO was 10 (range 3 to 25) months.

RESULTS

ΔFeNO-SS in 117 FeNO pairs was similar to ΔFeNO-SU in 26 pairs (2.1 ± 3 ppb vs 2.3 ± 4 ppb; p = 0.2). ΔFeNO-SAC in 17 pairs was markedly increased (27 ± 20 ppb; p < 0.001 vs ΔFeNO-SS). The area under the receiver-operating characteristic curve for ΔFeNO in detecting an acute complication was 0.93 (p < 0.001). By applying a cut-off of >10 ppb, the sensitivity and specificity was 82% and 100%, respectively, with positive and negative predictive values of 100% and 97.5%.

CONCLUSIONS

Changes in FeNO may serve as a useful adjunct in the detection of acute complications after lung transplantation. In this limited analysis, ΔFeNO was not predictive of a subsequent decline in allograft function.

Parametric response mapping as an indicator of bronchiolitis obliterans syndrome after hematopoietic stem cell transplantation

The management of bronchiolitis obliterans syndrome (BOS) after hematopoietic cell transplantation presents many challenges, both diagnostically and therapeutically. We developed a computed tomography (CT) voxel-wise methodology termed parametric response mapping (PRM) that quantifies normal parenchyma, functional small airway disease (PRM(fSAD)), emphysema, and parenchymal disease as relative lung volumes. We now investigate the use of PRM as an imaging biomarker in the diagnosis of BOS. PRM was applied to CT data from 4 patient cohorts: acute infection (n = 11), BOS at onset (n = 34), BOS plus infection (n = 9), and age-matched, nontransplant control subjects (n = 23). Pulmonary function tests and bronchoalveolar lavage were used for group classification. Mean values for PRM(fSAD) were significantly greater in patients with BOS (38% ± 2%) when compared with those with infection alone (17% ± 4%, P < .0001) and age-matched control subjects (8.4% ± 1%, P < .0001). Patients with BOS had similar PRM(fSAD) profiles, whether a concurrent infection was present or not. An optimal cut-point for PRM(fSAD) of 28% of the total lung volume was identified, with values >28% highly indicative of BOS occurrence. PRM may provide a major advance in our ability to identify the small airway obstruction that characterizes BOS, even in the presence of concurrent infection.

Clinical application of exhaled nitric oxide measurement in pediatric lung diseases

Fractional exhaled nitric oxide (FeNO) is a non invasive method for assessing the inflammatory status of children with airway disease. Different ways to measure FeNO levels are currently available. The possibility of measuring FeNO levels in an office setting even in young children, and the commercial availability of portable devices, support the routine use of FeNO determination in the daily pediatric practice. Although many confounding factors may affect its measurement, FeNO is now widely used in the management of children with asthma, and seems to provide significantly higher diagnostic accuracy than lung function or bronchial challenge tests. The role of FeNO in airway infection (e.g. viral bronchiolitis and common acquired pneumonia), in bronchiectasis, or in cases with diffuse lung disease is less clear. This review focuses on the most recent advances and the current clinical applications of FeNO measurement in pediatric lung disease.

Update on exhaled nitric oxide in pulmonary disease

The ability to assess the inflammatory status of a patient's airway using a noninvasive method is the ideal situation for clinicians. Owing in part to the relationship between the levels of exhaled nitric oxide to inflammation and the ease of the technique, the measurement of the fraction of exhaled nitric oxide (F(E)NO) has achieved considerable attention, particularly with respect to asthma. A multitude of studies have shown that when measured in exhaled air, this unique molecule has the potential to have both diagnostic and therapeutic roles in the clinical setting for many pulmonary diseases. The incorporation of F(E)NO into asthma management and treatment algorithms may help shed further insight on the current control and future risk of patients. Research is ongoing to determine the biology and the benefits of the use of F(E)NO in respiratory conditions in addition to asthma. This review will briefly outline the pathophysiology of nitric oxide, the measurement of F(E)NO and the potential clinical uses of F(E)NO in asthma and a number of other respiratory diseases. Despite its promise, until further research is conducted, the use of F(E)NO cannot be recommended for routine clinical management of respiratory diseases at present, but should be considered as an adjuvant to help guide therapy in certain patients with asthma and in those with eosinophilic bronchitis.

Exhaled nitric oxide and pulmonary complications after paediatric stem cell transplantation

Pulmonary complications are major causes of morbidity and mortality after haematopoietic stem cell transplantation (HSCT). We hypothesise that elevated exhaled nitric oxide (FeNO) levels early after HSCT in children are predictive for pulmonary complications. The present prospective study included 30 children (age, 4-18 years) before HSCT. FeNO levels were evaluated 10 days before transplant, at day 0, day +28 and day +60 after HSCT. During the follow-up period until day +100, pulmonary complications and lung function were assessed. Before HSCT, the mean FeNO levels were comparable in children with or without post-transplant pulmonary complications. However, they differed at day 0 and day +28 with a mean of 7 (±1.95) and 13 (±3.44) ppb at day 0 and a mean of 13 (±3.44) and 14 (±3.57) ppb at day +28, respectively.

CONCLUSION

Children with pulmonary complications after day +28 have higher mean FeNO levels 28 days after HSCT than children without later pulmonary complications. Therefore, FeNO could be an important diagnostic tool for hyperinflammatory response in bronchial epithelium after paediatric HSCT.