Complex lung physiology and airway inflammation in adults with asthma and fixed airflow obstruction

Background: Fixed airflow obstruction (FAO) occurs in asthma despite adequate treatment and no or minimal smoking history. FAO in asthma is more common in older people or those with long-standing disease and associated with poor outcomes. Airflow obstruction occurs in the small airways and is thought to be due to airway remodelling and driven by inflammation. Changes to the lung tissue, which may result in alteration of the lungs elastic properties such as loss of lung elastic recoil, may also contribute. The underlying mechanisms leading to FAO in asthma are poorly understood. Aim: To explore the physiological properties of both the airways and lung tissue and airway inflammation in older non-smokers with asthma, and to assess how they may contribute to FAO. Method: Non-smoking adults >40 years old with asthma were treated with two months of high dose inhaled corticosteroid/long-acting beta-agonist (ICS/LABA). Subsequently standard lung function and small airway function was measured using the forced oscillation technique (FOT) and the multiple breath nitrogen washout test (MBNW). Lung elastic recoil was measured using the oesophageal balloon technique. Airway inflammation was measured using bronchoalveolar lavage fluid obtained during bronchoscopy. Results: Non-smoking adults with asthma (n=19) demonstrated moderate FAO; small airway dysfunction, as measured by FOT and MBNW; increased lung compliance and loss of elastic recoil and variable airway inflammation. Worse airflow obstruction was associated with increased lung compliance. Increased airway resistance and small airway dysfunction in the acinar airways was associated with a loss of lung elastic recoil. Cross-sectional assessment of airway inflammation was not associated with lung function impairment. Conclusion: Changes to the lungs elastic properties results in increased compliance or reduced lung elastic recoil and make a significant contribution to FAO and small airway dysfunction in older non-smokers with asthma. ‘Lung remodelling’ is a potential pathological process leading to lung tissue changes and may be an alternate asthma paradigm. Underlying cellular mechanisms need further investigation

Dismantling airway disease with the use of new pulmonary function indices

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

Sustaining the Australian respiratory workforce through the COVID-19 pandemic: a scoping literature review

The outbreak of the COVID-19 pandemic in late 2019 and in 2020 presented challenges to healthcare workers (HCW) around the world that were unexpected and dramatic. The relentless progress of infection, starting in China and rapidly spreading to Europe, North America and elsewhere gave more remote countries, like Australia, time to prepare but also time for unease. HCW everywhere had to readjust and change their work practices to cope. Further waves of infection and transmission with newer variants pose challenges to HCW and health systems, even after mass vaccination. Respiratory medicine HCW found themselves at the frontline, developing critical care services to support intensive care units and grappling with unanticipated concerns about safety, risk and the need to retrain. Several studies have addressed the need for rapid changes in the healthcare workforce for COVID-19 and the impact of this preparation on HCW themselves. In this paper, we present a scoping review of the literature on preparing HCW for the pandemic, explore the Australian experience of building the respiratory workforce and propose evidence-based recommendations to sustain this workforce in an unprecedented high-risk environment

In vitro and in vivo functional residual capacity comparisons between multiple-breath nitrogen washout devices

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<0.0001) and −10.5±10.9% (p=0.005) using WIMR, EM, ndd v.2.00 and ndd v.2.01, respectively. Direct device comparison highlighted important differences in measurement accuracy. FRC discrepancies between devices were larger in vivo, compared to in vitro results; however, the pattern of difference was similar. These results represent progress in ongoing standardisation efforts

High rate of persistent symptoms up to 4 months after community and hospital-managed SARS-CoV-2 infection

Recovery after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection remains uncertain. A considerable proportion of patients experience persistent symptoms after SARS-CoV-2 infection which impacts health-related quality of life and physical function