Predictors of 30- and 90-Day COPD Exacerbation Readmission: A Prospective Cohort Study. Alqahtani JS, etal. Int J Chron Obstruct Pulmon Dis. 2021 Oct 7; 16:2769-81.

Background:   Readmission following COPD exacerbation is a common and challenging clinical problem. New approaches to predicting readmissions are required to help mitigate risk and develop novel interventions.

Methods:   We conducted a prospective cohort study in 82 COPD patients admitted due to an exacerbation of COPD. Lung function measures [spirometry, forced oscillation technique (FOT) indices and peak inspiratory flow rate (PIFR)], inflammatory biomarkers and patient-reported outcomes including previous exacerbation history, breathlessness, quality of life and frailty were measured at admission and discharge. We prospectively followed patients for 30 and 90 days to identify predictors for readmission.

Results:   The readmission rate within 30 days was 38%, and 56% within 90 days. Previous exacerbations, higher COPD Assessment Test score at discharge, frailty, reduced PIFR and increased length of stay were significantly associated with 30-day readmission. PIFR at discharge and frailty had the highest predictive ability for 30-day readmission using area under receiver operating characteristic curves (AUC 0.86, 95% CI 0.78-0.95, p < 0.001 and AUC 0.81, 95% CI 0.71-0.90, p < 0.001, respectively). Ninety-day readmissions were significantly associated with previous exacerbations and hospitalisations, higher CAT score at discharge, frailty, depression, lower PIFR and greater expiratory flow limitation (EFL) in the supine position. The best predictive variable in multivariable analysis for both 30- and 90-day readmission was PIFR at discharge.

Conclusion:   PIFR, CAT score, frailty, and EFL were found to be associated with 30- and 90-day readmission following COPD exacerbation. These findings help identify those at highest risk and to optimise care prior to discharge.

 

The clinical utility of forced oscillation technique during hospitalisation in patients with exacerbation of COPD. Alqahtani JS, etal. ERJ Open Res. 2021 Dec 20;7(4):00448-2021.

Background: Forced Oscillation Technique (FOT) is an innovative tool to measure within-breath reactance at 5 Hz (ΔXrs5Hz) but its feasibility and utility in acute exacerbations of COPD (AECOPD) is understudied.

Methods: A prospective observational study was conducted in 82 COPD patients admitted due to AECOPD. FOT indices were measured and the association between these indices and spirometry, peak inspiratory flow rate, blood inflammatory biomarkers and patient-reported outcomes including assessment of dyspnoea, quality of life, anxiety and depression and frailty at admission and discharge were explored.

Results: All patients were able to perform FOT in both sitting and supine position. The prevalence of expiratory flow limitation (EFL) in the upright position was 39% (32 out of 82) and increased to 50% (41 out of 82) in the supine position. EFL (measured by ΔXrs5Hz) and resistance at 5 Hz (Rrs5Hz) negatively correlated with forced expiratory volume in 1 s (FEV1); those with EFL had lower FEV1 (0.74±0.30 versus 0.94±0.36 L, p = 0.01) and forced vital capacity (1.7±0.55 versus 2.1±0.63 L, p = 0.009) and higher body mass index (27 (21-36) versus 23 (19-26) kg·m-2, p = 0.03) compared to those without EFL. During recovery from AECOPD, changes in EFL were observed in association with improvement in breathlessness.

Conclusion: FOT was easily used to detect EFL during hospitalisation due to AECOPD. The prevalence of EFL increased when patients moved from a seated to a supine position and EFL was negatively correlated with airflow limitation. Improvements in EFL were associated with a reduction in breathlessness. FOT is of potential clinical value by providing a noninvasive, objective and effort-independent technique to measure lung function parameters during AECOPD requiring hospital admission.

​

Small Airways Disease, Biomarkers and COPD: Where are We? Review. Chukowry PS, Spittle DA, Turner AM. Int J Chron Obstruct Pulmon Dis. 2021 Feb 18;16:351-365.

Cochrane Library search. published in the last 20 years.

The response to treatment and progression of COPD varies significantly. Small airways disease (SAD) is being increasingly recognized as a key pathological feature of COPD. Studies have brought forward pathological evidence of small airway damage preceding the development of emphysema and the detection of obstruction using traditional spirometry. In recent years, there has been a renewed interest in the early detection of SAD and this has brought along an increased demand for physiological tests able to identify and quantify SAD. Early detection of SAD allows early targeted therapy and this suggests the potential for altering the course of disease. The aim of this article is to review the evidence available on the physiological testing of small airways. The first half will focus on the role of lung function tests such as maximum mid-expiratory flow, impulse oscillometry and lung clearance index in detecting and quantifying SAD. The role of CT as a radiological biomarker will be discussed as well as the potential of recent CT analysis software to differentiate normal aging of the lungs to pathology. The evidence behind SAD biomarkers sourced from blood as well as biomarkers sourced from sputum and broncho-alveolar lavage (BAL) will be reviewed. This paper focuses on CC-16, sRAGE, PAI-1, MMP-9 and MMP-12.

Wei et al27 have shown that IOS had good correlation with the GOLD staging and several other studies have shown IOS to be more sensitive than spirometry in detecting small airways disease. For example, results obtained from 488 male firefighters found that IOS identified airway abnormalities even though spirometry results were within range.28 Mondal et al29 found that IOS was more sensitive than spirometry in detecting bronchodilator response in children with sickle-cell disease. Saadeh et al30 also showed that IOS had greater sensitivity than spirometry for monitoring bronchodilator response in patients with COPD. Data from the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) trial showed that smokers without COPD had an elevated AX (integrated area of low-frequency reactance which is a marker of small airway abnormality) but normal CT-scan densitometry. Moreover, although their FEV1 was within normal range, it was lower when compared to non-smoking controls.31 

• 27. Wei X, Shi Z, Cui Y, et al. Impulse oscillometry system as an alternative diagnostic method for chronic                     obstructive pulmonary disease. Medicine. 2017;96:46.

• 28. Schermer T, Malbon W, Newbury W. Spirometry and Impulse Oscillometry (IOS) for Detection of Respiratory         Abnormalities in Metropolitan Firefighters. Respirology. 2010;15:6.

• 29. Mondal P, Yirinec A, Midya V. Diagnostic value of spirometry vs impulse oscillometry: a comparative study in           children with sickle cell disease. Pediatr Pulmonol. 2019;54:9.

• 30. Midya V. Advantage of impulse oscillometry over spirometry to diagnose chronic obstructive pulmonary               disease  and monitor pulmonary responses to bronchodilators: an observational study. SAGE Open Med.             2015;3.

• 31. Crim C, Celli B, Edwards LD, et al. Respiratory system impedance with impulse oscillometry in healthy and            COPD subjects: ECLIPSE baseline results. Respir Med. 2011;105(7):1069–1078.

 

Pulmonary function testing in COPD: looking beyond the curtain of FEV1. Review. Kakavas S, etal. NPJ Prim Care Respir Med. 2021 May 7;31(1):23.

Small airway disease is a silent signature of early COPD that is likely to be directly or indirectly captured by combinations of physiological tests, ... Oscillometry is more sensitive than spirometry in identifying peripheral airway pathology43,45. Importantly, IOS can differentiate small airway obstruction from large airway obstruction and is more sensitive than spirometry for peripheral airway disease90. Notably, it can detect early lung dysfunction in smokers, long before any clinical symptoms of COPD arise95. FOT findings in COPD consist of an increased Rrs and a decreased Xrs value, culminating in an increased expiratory Zrs89. These findings are suggestive of small airway obstruction and, importantly, Zrs values correlate to the severity of airway narrowing96. Furthermore, FOT is more sensitive than FEV1 in detecting expiratory flow limitation, an indicator of dynamic hyperinflation characteristically present in COPD patients during exertion97. It has been recently suggested that IOS may be used alternatively to other PFTs in patients with FEV1 lower than 50%98. Yamagami et al., proved that FOTparameters differ between COPD patients with frequent exacerbations and those having a less eventful disease course. Consequently, patients identified as frequent exacerbators can be monitored more closely and treated accordingly99. In the Eclipse study, one of the largest COPD studies, with a 2,054 cohort of COPD patients, it has been shown that changes in oscillometric parameters tend to correlate well with GOLD severity.

• 43. Lee, J. et al. Graphic analysis of flow-volume curves: a pilot study. BMC Pulm. Med. 16, 18 (2016). 44. Mochizuki, F. et al. The concavity of the maximal expiratory flow–volume curve reflects the extent of emphysema in obstructive lung diseases. Sci. Rep. 9, 13159 (2019).

• 45. Thorat, Y. T., Salvi, S. S. & Kodgule, R. R. Peak flow meter with a questionnaire and mini-spirometer to help detect asthma and COPD in real-life clinical practice: a cross-sectional study. NPJ Prim. Care Respir. Med. 27, 32 (2017).

• 89. Oostveen, E. et al. The forced oscillation technique in clinical practice: methodology, recommendations and future developments. Eur. Respir. J. 22, 1026–1041 (2003).

• 90. . H.J. Smith, P. Reinhold and M.D. Goldman. Forced oscillation technique and impulse oscillometry. In:  Lung Function Testing. Gosselink, R. & Stam, Heditors. Europ. Respir. Monograms, 2005 Apr; 10: Chp 5: 

• 95. Shinke, H. et al. Visualized changes in respiratory resistance and reactance along a time axis in smokers: a cross-sectional study. Respir. Investig. 51, 166–174 (2013).

• 96. Tse, H. N., Tseng, C. Z. S., Wong, K. Y., Yee, K. S. & Ng, L. Y. Accuracy of forced oscillation technique to assess lung function in geriatric COPD population. Int. J. Chron. Obstruct. Pulmon. Dis. 11, 1105–1118 (2016).

• 97. Dellacà, R. L. et al. Detection of expiratory flow limitation in COPD using the forced oscillation technique. Eur. Respir. J. 23, 232–240 (2004).

• 98. Wei, X. et al. Impulse oscillometry system as an alternative diagnostic method for chronic obstructive pulmonary disease. Medicine 96, e8543 (2017).

• 99. Yamagami, H. et al. Association between respiratory impedance measured by forced oscillation technique and exacerbations in patients with COPD. Int. J. Chron. Obstruct. Pulmon. Dis. 13, 79–89 (2018).

 

​