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Peak spirometry after single lung transplantation (SLTx) for interstitial lung disease (ILD) is lower than after double lung transplantation (DLTx), however the pathophysiologic mechanisms are unclear. We aim to assess respiratory mechanics in SLTx and DLTx for ILD using oscillometry. Spirometry and oscillometry (tremoflo® C-100) were performed in stable SLTx and DLTx recipients in a multi-center study. Resistance (R5, R5–19) and reactance (X5) were compared between LTx recipient groups, matched by age and gender. A model of respiratory impedance using ILD and DLTx data was performed. In total, 45 stable LTx recipients were recruited (SLTx n = 23, DLTx n = 22; males: 87.0% vs. 77.3%; median age 63.0 vs. 63.0 years). Spirometry was significantly lower after SLTx compared with DLTx: %-predicted mean (SD) FEV1 [70.0 (14.5) vs. 93.5 (26.0)%]; FVC [70.5 (16.8) vs. 90.7 (12.8)%], p < 0.01. R5 and R5–19 were similar between groups (p = 0.94 and p = 0.11, respectively) yet X5 was significantly worse after SLTx: median (IQR) X5 [−1.88 (−2.89 to −1.39) vs. −1.22 (−1.87 to −0.86)] cmH2O.s/L], p < 0.01. R5 and X5 measurements from the model were congruent with measurements in SLTx recipients. The similarities in resistance, yet differences in spirometry and reactance between both transplant groups suggest the important contribution of elastic properties to the pathophysiology. Oscillometry may provide further insight into the physiological changes occurring post-LTx.

Abstract Asthma with irreversible or fixed airflow obstruction (FAO) is a severe clinical phenotype that is difficult to treat and is associated with an accelerated decline in lung function and excess morbidity. There are no current treatments to reverse or prevent this excessive decline in lung function in these patients, due to a lack of understanding of the underlying pathophysiology. The current paradigm is that FAO in asthma is due to airway remodeling driven by chronic inflammation. However, emerging evidence indicates significant and critical structural and functional changes to the lung parenchyma and its lung elastic properties in asthma with FAO, suggesting that FAO is a ‘whole lung’ problem and not just of the airways. In this Perspective we draw upon what is known thus far on the pathophysiological mechanisms contributing to FAO in asthma, and focus on recent advances and future directions. We propose the view that structural and functional changes in parenchymal tissue, are just as (if not more) important than airway remodeling in causing persistent lung function decline in asthma. We believe this paradigm of FAO should be considered when developing novel treatments.

We are currently limited in our abilities to diagnose, monitor disease status and manage chronic airway disease like asthma and chronic obstructive pulmonary disease (COPD). Conventional lung function measures often poorly reflect patient symptoms or are insensitive to changes, particularly in the small airways where disease may originate or manifest. Novel pulmonary function tests are becoming available which help us better characterise and understand chronic airway disease, and their translation and adoption from the research arena would potentially enable individualised patient care. In this article, we aim to describe two emerging lung function tests yielding novel pulmonary function indices, the forced oscillation technique (FOT) and multiple breath nitrogen washout (MBNW). With a particular focus on asthma and COPD, this article demonstrates how chronic airway disease mechanisms have been dismantled with the use of the FOT and MBNW. We describe their ability to assess detailed pulmonary mechanics for diagnostic and management purposes including response to bronchodilation and other treatments, relationship with symptoms, evaluation of acute exacerbations and recovery, and telemonitoring. The current limitations of both tests, as well as open questions/directions for further research, are also discussed.

Functional residual capacity (FRC) accuracy is essential for deriving multiple-breath nitrogen washout (MBNW) indices, and is the basis for device validation. Few studies have compared existing MBNW devices. We evaluated in vitro and in vivo FRC using two commercial MBNW devices, the Exhalyzer D (EM) and the EasyOne Pro LAB (ndd), and an in-house device (Woolcock in-house device, WIMR). FRC measurements were performed using a novel syringe-based lung model and in adults (20 healthy and nine with asthma), followed by plethysmography (FRCpleth). The data were analysed using device-specific software. Following the results seen with ndd, we also compared its standard clinical software (ndd v.2.00) with a recent upgrade (ndd v.2.01). WIMR and EM fulfilled formal in vitro FRC validation recommendations (>95% of FRC within 5% of known volume). Ndd v.2.00 underestimated in vitro FRC by >20%. Reanalysis using ndd v.2.01 reduced this to 11%, with 36% of measurements ≤5%. In vivo differences from FRCpleth (mean±sd) were 4.4±13.1%, 3.3±11.8%, −20.6±11% (p