Significance of Best Spirometry in the First Year After Bilateral Lung Transplantation: Association With 3-Year Outcomes

Alterations in Pulmonary Physiology with Lung Transplantation

Lung transplant is a treatment option for patients with end-stage lung diseases; however, survival outcomes continue to be inferior when compared to other solid organs. We review the several anatomic and physiologic changes that result from lung transplantation surgery, and their role in the pathophysiology of common complications encountered by lung recipients. The loss of bronchial circulation into the allograft after transplant surgery results in ischemia-related changes in the bronchial artery territory of the allograft. We discuss the role of bronchopulmonary anastomosis in blood circulation in the allograft posttransplant. We review commonly encountered complications related to loss of bronchial circulation such as allograft airway ischemia, necrosis, anastomotic dehiscence, mucociliary dysfunction, and bronchial stenosis. Loss of dual circulation to the lung also increases the risk of pulmonary infarction with acute pulmonary embolism. The loss of lymphatic drainage during transplant surgery also impairs the management of allograft interstitial fluid, resulting in pulmonary edema and early pleural effusion. We discuss the role of lymphatic drainage in primary graft dysfunction. Besides, we review the association of late posttransplant pleural effusion with complications such as acute rejection. We then review the impact of loss of afferent and efferent innervation from the allograft on control of breathing, as well as lung protective reflexes. We conclude with discussion about pulmonary function testing, allograft monitoring with spirometry, and classification of chronic lung allograft dysfunction phenotypes based on total lung capacity measurements. We also review factors limiting physical exercise capacity after lung transplantation, especially impairment of muscle metabolism. © 2023 American Physiological Society. Compr Physiol 13:4269-4293, 2023.

Airway oscillometry parameters in baseline lung allograft dysfunction: Associations from a multicenter study

BACKGROUND

Baseline lung allograft dysfunction (BLAD), the failure to achieve ≥80%-predicted spirometry after lung transplant (LTx), is associated with impaired survival. Physiologic abnormalities in BLAD are poorly understood. Airway oscillometry measures respiratory system mechanics and may provide insight into understanding the mechanisms of BLAD.

OBJECTIVES

This study aims to describe and measure the association between airway oscillometry parameters [Reactance (X_rs5, Ax), Resistance (R_rs5, R_rs5-19)] (1) stable LTx recipients, comparing those with normal spirometry and those with BLAD; and (2) in recipients with chronic lung allograft dysfunction (CLAD), comparing those with normal baseline spirometry and those with BLAD.

METHODS

A multi-center cross-sectional study was performed including bilateral LTx between January 2020 and June 2021. Participants performed concurrent airway oscillometry and spirometry. Multivariable logistic regression was performed to measure the association between oscillometry parameters and BLAD.

RESULTS

A total of 404 LTx recipients performed oscillometry and 253 were included for analysis. Stable allograft function was confirmed in 149 (50.2%) recipients (92 (61.7%) achieving normal spirometry and 57 (38.3%) with BLAD). Among stable LTx recipients, lower X_rs5 Z-Score (aOR 0.50 95% CI 0.37-0.76, p = 0.001) was independently associated with BLAD. CLAD was present in 104 (35.0%) recipients. Among recipients with CLAD, lower X_rs5 Z-Score (aOR 0.73 95% CI 0.56-0.95, p = 0.02) was associated with BLAD.

CONCLUSIONS

Oscillometry provides novel physiologic insights into mechanisms of BLAD. The independent association between X_rs5 and BLAD, in both stable recipients and those with CLAD suggests that respiratory mechanics, in particular abnormal elastance, is an important physiologic feature. Further longitudinal studies are needed to understand the trajectory of oscillometry parameters in relation to allograft outcomes.

NKG2D receptor activation drives primary graft dysfunction severity and poor lung transplantation outcomes

Clinical outcomes after lung transplantation, a life-saving therapy for patients with end-stage lung diseases, are limited by primary graft dysfunction (PGD). PGD is an early form of acute lung injury with no specific pharmacologic therapies. Here, we present a large multicenter study of plasma and bronchoalveolar lavage (BAL) samples collected on the first posttransplant day, a critical time for investigations of immune pathways related to PGD. We demonstrated that ligands for NKG2D receptors were increased in the BAL from participants who developed severe PGD and were associated with increased time to extubation, prolonged intensive care unit length of stay, and poor peak lung function. Neutrophil extracellular traps (NETs) were increased in PGD and correlated with BAL TNF-α and IFN-γ cytokines. Mechanistically, we found that airway epithelial cell NKG2D ligands were increased following hypoxic challenge. NK cell killing of hypoxic airway epithelial cells was abrogated with NKG2D receptor blockade, and TNF-α and IFN-γ provoked neutrophils to release NETs in culture. These data support an aberrant NK cell/neutrophil axis in human PGD pathogenesis. Early measurement of stress ligands and blockade of the NKG2D receptor hold promise for risk stratification and management of PGD.

Influence of Bronchoscopic Interventions on Graft Function of Double Lung Transplant Recipients due to Cystic Fibrosis

BACKGROUND

Healing of bronchial anastomoses may sometimes be complicated and require bronchoscopic intervention (BI). The main aim of the study was to assess whether patients who require BI present comparable lung function after reaching 1-year posttransplant survival to those who did not require any BI by means of spirometry and 6-minute walk test (6MWT).

METHODS

This retrospective study included an analysis of 44 primary double lung transplant recipients who underwent transplant for end-stage respiratory failure in the course of cystic fibrosis transplanted in a single center between 2018 and 2021. Bronchoscopic intervention is defined as performing endoscopic bronchoplasty through balloon dilatation, cryoprobe, argon plasma, and/or laser treatment. Group 1 (25 patients who required at least 1 BI) presented similar spirometry parameters at qualification as group 2 (no BI).

RESULTS

Statistically significant differences between the groups for the following parameters were reported: forced expiratory volume in 1 second (FEV1), FEV1 (%), Tiffeneau-Pinelli index (FEV1/forced vital capacity percentage of predicted value), oxygen saturation after conclusion of 6MWT (%) and oxygen saturation before 6MWT (%). In each case, the mean for the BI group in the first year was lower. All patients in this group received an average amount of 6.8 ± 4.9 bronchoscopic procedures during the first year (minimum = 1; maximum = 18). Strong negative correlations were observed between the number of balloons in the first year and the FEV1 (%) and FEV1/forced vital capacity percentage of predicted value indicators after the first year.

CONCLUSIONS

Lung transplant recipients who underwent transplant because of cystic fibrosis and required at least 1 BI during the first posttransplant year presented inferior spirometry and 6MWT results in comparison with those who did not require any.

COVID-19 in lung transplant recipients: an overview of the Swedish national experience

Although it is known that solid organ transplant recipients fare worse after COVID-19 infection, data on the impact of COVID-19 on clinical outcomes and allograft function in lung transplant (LTx) recipients are limited and based mainly on reports with short follow-up. In this nationwide study, all LTx recipients with COVID-19 diagnosed from 1 February 2020 to 30 April 2021 were included. The patients were followed until 1 August 2021 or death. We analysed demographics, clinical features, therapeutic management and outcomes, including lung function. Forty-seven patients were identified: median age was 59 (10-78) years, 53.1% were male, and median follow-up was 194 (23-509) days. COVID-19 was asymptomatic or mild at presentation in 48.9%. Nine patients (19.1%) were vaccinated pre-COVID infection. Two patients (4.3%) died within 28 days of testing positive, and the overall survival rate was 85.1%. The patients with asymptomatic or mild symptoms had a higher median % expected forced expiratory volume during the first second than the patients with worse symptoms (P = 0.004). LTx recipients develop the entire spectrum of COVID-19, and in addition to previously acknowledged risk factors, lower pre-COVID lung function was associated with more severe disease presentation.

Spectrum of findings on ventilation‒perfusion lung scintigraphy after lung transplantation and association with outcomes

BACKGROUND

Air trapping (AT) is one of the hallmarks of allograft dysfunction after lung transplantation (LT). Inert gas‒based ventilation‒perfusion (VQ) lung scintigraphy has excellent sensitivity in the detection of AT.

METHODS

We reviewed the charts of patients who underwent single or double LT between January 2012 and December 2014 (N = 193). Patients without a VQ scintigraphy at the first annual visit (n = 16) and those who did not survive till 1 year (n = 26) were excluded (final n = 151, mean age = 55.8 [SD =14] years, male = 85, female = 66). VQ scintigraphy was independently reviewed and reconciled for the presence and severity of AT by 2 investigators blinded to the clinical data (D.F.P. and D.M.). A 3-year post-transplant survival was the primary end-point.

RESULTS

AT was common (n = 73, 48.3%). Patients with obstructive lung diseases as the underlying diagnosis (adjusted odds ratio [OR], 4.36, 95% CI: 1.64‒11.6; p = 0.003) and those with lower body mass index (BMI) (BMI < 25 kg/m² and 25‒30 kg/m²; p < 0.001) had an increased risk of developing AT in the allograft. The presence of AT (adjusted OR, 2.33, 95% CI: 1.01‒5.36; p = 0.04) and peak forced expiratory volume in 1 sec (FEV₁) <60% predicted during the first year after LT were independently associated with 3-year mortality. The association of AT with post-transplant mortality was the strongest among patients with BMI <30 kg/m² and peak FEV₁ <60% predicted.

CONCLUSIONS

The finding of AT on VQ scintigraphy at the first annual visit after LT is independently associated with worse post-transplant mortality. The sub-group of patients who fail to achieve a peak FEV₁ of 60% predicted during the first year after LT appears to be the key driver of this association.

Number of Bronchoscopic Interventions in Lung Transplant Recipients Correlates with Respiratory Function Assessed by Pulmonary Function Tests

Background

Lung transplant recipients may suffer from airway stenosis (AS). The aim of this study was to assess whether pulmonary function (as measured by spirometry and a 6-minute walk test [6MWT]) in patients with AS treated consistently with bronchoscopic interventions (BIs) was comparable to that in their AS-free counterparts at the 1-year follow-up visit.

Material/Methods

Fifty patients who underwent primary double-lung transplantation between January 2015 and March 2019 at a single center (23 who received BIs and 27 who did not) were enrolled in this retrospective study. Graft function was assessed with spirometry, based on forced expiratory volume (FEV₁) and forced vital capacity (FVC), both measured in liters (L) and percentages (%), and the Tiffeneau-Pinelli index (FEV₁/FVC), and a 6MWT and parameters such as oxygen saturation measured before and after the test.

Results

Patients in need of BIs had significantly lower FEV₁% compared with individuals who did not receive BIs during their first post-transplant year. Airway obstruction was present in 22% of patients who did not receive BIs and 65.23% of those who did receive the interventions. There were statistically significant, strong, negative correlations pertaining to the number of balloon BIs and 1-year FEV₁% (r_s=0.67) as well as the number of balloon BIs and 1-year FEV₁/FVC (r_s=0.72). A statistically significant, strong, negative correlation (r_s=0.75) was found between the number of balloon bronchoplasty treatments and oxygen saturation after the 6WMT.

Conclusions

Despite receiving BIs, patients who experience bronchial stenosis may not obtain the expected ventilatory improvement at their 1-year follow-up visit. Their AS may recur or persist despite use of various procedures. Further study in that regard is required.