Within-session variability as quality control for oscillometry in health and disease

Multiple breath washout and oscillometry after allogenic HSCT: a scoping review

Pulmonary chronic graft-versus-host disease (cGVHD) is a substantial cause of pulmonary morbidity and mortality post-haematopoietic stem cell transplantation (HSCT). Current spirometry-based monitoring strategies have significant limitations. Understanding the utility of novel peripheral airway function tests - multiple breath washout (MBW) and oscillometry - is critical in efforts to improve detection, facilitate earlier intervention and improve outcomes. In this scoping review, we identified 17 studies investigating MBW or oscillometry, or both, after allogenic HSCT. Despite small study numbers limiting the ability to draw firm conclusions, several themes were evident. Detectable peripheral airway abnormality in MBW occurred in a substantial proportion prior to HSCT. MBW indices post-HSCT were more frequently abnormal than spirometry when reporting group data and among those with extrapulmonary cGVHD and pulmonary cGVHD. Changes in MBW indices over time may be more indicative of pulmonary complications than absolute values at any given time point. Oscillometry indices were often normal at baseline, but more frequently abnormal in those who developed pulmonary cGVHD. Pooling currently available individual participant data across these studies may improve our ability to formally compare their respective sensitivity and specificity at specific time points and assess the trajectory of MBW and oscillometry indices over time.

Quality control in respiratory oscillometry: reproducibility measures ignoring reactance?

This study demonstrates the inadequacy of the current technical standards of oscillometry that are based on the within-trial reproducibility of the lowest-frequency R_rs, and suggests the use of a simple variability measure encompassing both R_rs and X_rs https://bit.ly/3AYRid6.

An analysis of alternative forced oscillation technique reporting and validation methods for within- and between-sessions in healthy adults

Forced oscillation technique (FOT) provides unique information on respiratory system mechanical properties complementing pulmonary function testing. However, a lack of evidence guiding acquisition/reporting of parameters has slowed clinical FOT adoption. Current European Respiratory Society (ERS) standards recommend 3-5 trials per session comprising three trials with a coefficient of variation (CoV) ≤ 10% for low-frequency resistance. We present an analysis of different combinations of trial selection methods and session validity thresholding variables (low- and mid-frequency resistance and reactance [R5, R19, X5], low-frequency reactance area [AX] and tidal volume) comparing proportion of subjects achieving valid data across two test sessions (7 ± 3 days apart) and within and between session measurement variabilities. 126 (98%) subjects achieved valid data across both sessions (2666 trials). With R5 or R19 as criteria and selection of any three trials from ≥ 4 attempts, ≥ 75% of subjects achieved validity. Furthermore, with R5 or R19 criteria and selection of any trials from ≥ 5 attempts, CoVs for resistance outcomes were reduced within session while variabilities of FOT outcomes between sessions remained consistent. Within session differences in measurement variabilities were not clinically meaningful. Our analyses support current ERS reporting recommendations for healthy adults. Future work should apply this analytic approach to patient populations.

Quality assessment pathway for respiratory oscillometry

There is strong evidence to support the addition of respiratory oscillometry to standard lung function testing. The key parameters are sensitive in identifying the presence and severity of airways disease [1], and clinically meaningful cut-offs have been established to identify bronchodilator response [2] and bronchial hyperresponsiveness [3–6] independent of spirometry. While clinical uptake is increasing with the availability of commercial devices, oscillometry is yet to be widely adopted as a standard test. This has been in part due to a lack of standardisation in equipment specifications and inconsistent terminology, but also human-related factors such as measurement protocols and objective quality control. The recently published international technical standards [7] have partly addressed most of these issues, and the development of global reference equations is currently in progress. Nevertheless, there remains a strong need to develop standard methods to optimise measurement quality and operator competency.

A flow-chart-driven procedure is presented to facilitate respiratory oscillometry operator competency and measurement quality. A novel feature is a quality grading system, in line with other standards of lung function.https://bit.ly/3G4r0X1