Bronchodilator response at low lung volumes predicts bronchiolitis obliterans in lung transplant recipients

Decline in 25% to 75% forced expiratory flow as an early predictor of chronic airway rejection in pediatric lung transplant recipients

BACKGROUND

Bronchiolitis obliterans (BO) is the major obstacle to long-term lung allograft viability. Its clinical correlate, BO syndrome (BOS), is defined as a decline of at least 20% in forced expiratory volume in 1 second (FEV(1)) from baseline. BOS is often diagnosed after significant organ dysfunction has occurred. Because BO is a small-airways disease, we hypothesized that a 20% decline in the 25% to 75% forced expiratory flow (FEF(25-75)) from baseline should occur before a decline in FEV(1) and should predict progression to BOS with high sensitivity and specificity.

METHODS

Pulmonary function tests and records of pediatric lung transplantation patients at Texas Children's Hospital from 2002 to 2007 were reviewed. Declines in FEV(1) and FEF(25-75) from the best post-transplant baseline values were recorded and analyzed. Sensitivity, specificity, and positive and negative predictive values were calculated.

RESULTS

Thirty-one patients were eligible for the study. In 11 BOS patients, the mean±standard deviation number of days from transplant until a 20% decline in FEV(1) was 896.5±400 compared with 728.0±475 (p = 0.022) until a 20% decline in FEF(25-75) was reached. The sensitivity, specificity, and positive predictive and negative predictive values of a 20% reduction in FEF(25-75) in determining BOS were 100%, 90.0%, 84.6%, and 100%, respectively.

CONCLUSIONS

All patients who developed BOS had a decline in FEF(25-75) at or before the decline in FEV(1). The reduction in FEF(25-75) occurred statistically significantly earlier than the decline in FEV(1), by an average of 168.5 days. This decline in FEF(25-75) was also highly sensitive and specific for the diagnosis of BOS.

High-dose corticosteroid therapy for bronchiolitis obliterans after bone marrow transplantation in children

Bronchiolitis obliterans (BO) is a rare but serious complication of paediatric allogenic bone marrow transplantation (BMT). Currently, there is no clear evidence that therapeutic interventions have a positive impact on the course of the disease. We here report our experience with high-dose pulse methylprednisolone therapy in children after BMT. Nine patients fulfilling clinical and radiologic signs of BO were included in this analysis. The total amount of treatment cycles with pulse methylprednisolone therapy ranged from 1 to 6 cycles (median four cycles). Oxygen saturation increased significantly with normalization of oxygen saturation at the end of therapy in all individuals. Normal oxygen saturation was maintained in all but one patient during follow-up (mean follow-up period 42 {plus/minus} 20 months, range 19-67 months). Forced expiratory volume in 1 s (FEV1) was within the normal range prior BMT and significantly diminished at the time of BO diagnosis. Treatment led to stabilization of lung function, with a significant improvement of FEV1 after 2 months. In all, 7/9 patients remained in clinically stable condition without further deterioration of lung function during follow-up. These data would suggest that anti-inflammatory therapy may be a valuable treatment option in paediatric patients with bronchiolitis obliterans after BMT.

A Descriptive Study of Small Airway Reticular Basement Membrane Thickening in Clinically Stable Lung Transplant Recipients

BACKGROUND

Chronic rejection functionally manifested by fixed airflow limitation, bronchiolitis obliterans syndrome (BOS), is a major problem for all lung allograft programs. The inclusion of a pre-BOS category (BOS(0 approximately p)) in the newly revised guidelines, recognizes the potential importance of early changes. We tested the hypothesis that small airway reticular basement membrane thickening exists even in clinically stable lung transplant recipients with some evidence of inflammation but who are BOS-free.

METHODS

A bronchoscopic study was performed on 30 clinically stable lung allograft recipients at >/=3 months post-allograft, who were BOS-free but with some evidence of airway inflammation indicated by a pathologic diagnosis of lymphocytic bronchiolitis or raised exhaled nitric oxide (NO). After baseline physiologic assessment, small airway reticular basement membrane (Rbm) thickening was quantified in transbronchial biopsy (TBB) using image analysis, with inflammation assessed by bronchoalveolar lavage (BAL) differential cell counts.

RESULTS

Twenty-one patients had technically satisfactory measurements of Rbm thickness. We detected small airway Rbm thickening when compared with published data for control lung diseases. There was no correlation between Rbm thickening and lung function (forced expiratory volume in 1 second [FEV(1)] best post-operatively and Rbm r = -0.10, not significant).

CONCLUSIONS

Our data suggest that airway remodeling can occur early in lung allografts and before development of airflow limitation and BOS. Longitudinal pathophysiologic studies are needed to elucidate potential relationships between airway inflammation, Rbm thickening and allograft failure. Airway biopsies would be of value in such studies.

Surrogate markers and risk factors for chronic lung allograft dysfunction

Obliterative bronchiolitis (OB) is the histologic correlate of chronic allograft dysfunction in pulmonary transplantation. The histologic diagnosis of OB is challenging, therefore a physiologic definition, bronchiolitis obliterans syndrome (BOS) based on pulmonary function tests has been used as a surrogate marker for OB for the last decade. BOS has proven to be the best available surrogate marker for OB and is predictive of the ultimate endpoints of graft and patient survival. Multiple other clinical markers have been reported and proposed as alternates for or complements to BOS grade, but all need further evaluation and validation in large, prospective clinical trials. Lastly, given the early occurrence and high incidence of chronic allograft dysfunction, the easily measurable endpoint of BOS grade, and our lack of understanding of ways to prevent or alter the course of BOS, lung transplant recipients represent an ideal population for clinical trials targeting prevention and treatment of chronic allograft dysfunction.

Bronchiolitis obliterans

PURPOSE OF REVIEW

Bronchiolitis obliterans (BO) occurs in both post-lung transplant and nontransplant-related individuals, and is characterized by mainly irreversible airflow obstruction that is often ultimately progressive.

RECENT FINDINGS

While post-lung transplant BO is a major cause of lung allograft dysfunction, and hence is better characterized than nontransplant-related BO, it is likely that many similarities in pathogenesis and treatment apply to both categories.

SUMMARY

Optimal management for BO remains to be established, and the role of retransplantation in this disease requires further consensus. Minimization of risk factors for BO and earlier detection in the form of methacholine challenge testing and HRCT scans of the chest amongst other forms of detection, may help in the stabilization and possible resolution of early BO.

Air trapping in heart-lung transplant recipients: variability of anatomic distribution and extent at sequential expiratory thin-section CT

PURPOSE

To evaluate the intrapatient reproducibility of the extent and anatomic distribution of air trapping at sequential expiratory thin-section computed tomographic (CT) examinations in heart-lung transplant recipients.

MATERIALS AND METHODS

Nineteen heart-lung transplant recipients (eight with and 11 without bronchiolitis obliterans syndrome [BOS]) underwent three expiratory CT examinations within 1 hour. Residual volumes were measured at CT. Anatomic distribution and extent of air trapping were scored by two observers at two independent readings, and the reproducibility of observations was calculated for each feature. CT examination results were compared by using an analysis of variance that took into account interobserver and BOS and non-BOS effects. The Spearman rank correlation coefficient was calculated to test the association between variability of residual volumes and variability of the extent of air trapping.

RESULTS

Residual volumes did not significantly differ between the three CT examinations (P =.556). Reproducibility values for findings of anatomic distribution of air trapping ranged from 84% to 95%, with a tendency toward improved reproducibility in patients without BOS. Mean reproducibility values for the extent of air trapping ranged from 97.1% to 97.7%, and no substantial difference in these values between patients with and those without BOS was observed. The Spearman rank coefficient for the correlation between variability of residual volumes and variability of extent of air trapping ranged from 0.382 to 0.568 (P =.105-.016). No interobserver effect was detected (P =.944).

CONCLUSION

Anatomic distribution and extent are reproducible characteristics of air trapping. No substantial variability of air trapping occurs in functionally stable heart-lung transplant recipients.

Involvement of peripheral airways during methacholine-induced bronchoconstriction after lung transplantation

Previous studies have shown that the presence of nonspecific bronchial hyperreactivity (NSBHR) in transplanted subjects is associated with the development of bronchiolitis obliterans, which suggests that NSBHR in these subjects may involve the peripheral airways. We investigated this question by studying the effects of methacholine on the distribution of ventilation using single-breath washouts in 15 heart-lung transplant recipients; 17 nontransplanted subjects with NSBHR were studied for comparison. All subjects had normal baseline lung function, and seven transplanted subjects displayed NSBHR. Methacholine induced a similar decline in FEV1 and specific airway conductance in the two groups. In contrast, whereas methacholine produced similar increases in the slope of the alveolar plateau for SF6 (SSF6) and He (SHe) in the nontransplanted subjects, it always produced greater increases in SHe than SSF6 in the transplanted subjects. This suggests that in the latter, methacholine-induced bronchoconstriction made the distribution of ventilation more heterogeneous in peripheral airways. This involvement of small airways may help in understanding why assessing bronchial reactivity in transplanted subjects provides information on the presence of a pathologic process affecting the bronchioles, and hence on the risk of progression to bronchiolitis obliterans.

Bronchiolitis obliterans syndrome in heart-lung transplant recipients: diagnosis with expiratory CT

PURPOSE

To determine the test performance and longitudinal evolution of air trapping for diagnosing bronchiolitis obliterans syndrome (BOS).

MATERIALS AND METHODS

Over 7 years, 111 combined inspiratory and expiratory computed tomographic examinations were performed in eight healthy control subjects and 38 heart-lung transplant recipients. Functional impairment was assessed with the BOS classification. Receiver operating characteristic (ROC) analysis was performed to determine the optimal threshold of air trapping to distinguish between patients with and those without BOS and to compute sensitivity and specificity for diagnosing BOS.

RESULTS

The extent of air trapping increased with BOS severity (P =.001). A threshold of 32% of air trapping is optimal for distinguishing between patients with and those without BOS and provides a sensitivity of 83%, a specificity of 89%, and an accuracy of 88%. The prevalence of BOS and positive predictive value of air trapping increased with postoperative time, but the negative predictive value of air trapping remained high throughout the study. Patients without BOS who had air trapping exceeding 32% of the parenchyma were at significantly increased risk of developing BOS (P =.004).

CONCLUSION

At the threshold of 32%, air trapping is sensitive, specific, and accurate for diagnosing BOS. Patients with air trapping below 32% are unlikely to have BOS. Air trapping exceeding 32% may be an early indicator of future BOS.

Bronchial hyperreactivity after lung transplantation predicts early bronchiolitis obliterans

Nonspecific bronchial hyperreactivity (NSBHR) has been observed in patients who have undergone lung transplantation, but studies have provided conflicting reports as to the incidence and significance of this finding. To delineate more clearly the natural history of NSBHR after lung transplantation, data from 111 consecutive patients undergoing double lung transplantation between February 1988 and May 1994 were reviewed. Methacholine challenge testing was requested in conjunction with regular postoperative follow-up. Among 60 patients tested at 3 mo, 18 (30%) had a positive methacholine challenge; at 6 mo, the incidence was 14 of 59 (24%). Of 21 patients for whom complete testing was performed for 12 mo or longer, 13 (62%) had exclusively negative challenges. Patients with a positive challenge at 3 mo were significantly more likely to develop bronchiolitis obliterans syndrome (BOS) (p < 0.006). Mean time to development of BOS was 16.9 mo in the group with positive challenges versus 43.9 mo for those with negative challenges. We conclude that increased NSBHR is a common, but by no means universal, finding after lung transplantation. Furthermore, early positive methacholine challenges are associated with development of BOS. We hypothesize that NSBHR may represent an early marker of chronic rejection in these patients.