The validity of shortened multiple-breath washout testing using sulfur hexafluoride in the assessment of patients with COPD.

INTRODUCTION: COPD affects the small airways and is associated with ventilation heterogeneity. There are little data on the multiple-breath washout (MBW) in patients with COPD, particularly the variability over 8 weeks, using a shortened sulfur hexafluoride (SF6) washout. This work evaluated the repeatability of the lung clearance index (LCI)1/40 and LCI1/20 among subjects with COPD and compared to spirometry and clinical markers. METHODS: The MBW was performed on patients with COPD to determine ventilation heterogeneity globally (LCI), at conductive (Scond) and acinar (Sacin) levels. The LCI was repeated in triplicate and measured at a traditional 1/40th washout and retrofitted to a shortened 1/20th end tidal SF6 concentration washout. Tests were repeated after 20 min and 8  weeks to determine within and between visit repeatability and compared with spirometry. RESULTS: Eighty-four subjects were recruited to perform LCI and spirometry with 20 subjects performing the repeatability protocol. There were weak correlations between forced expiratory volume in 1 s ( FEV1) per cent predicted and LCI1/40th r=-0.311 (p=0.02), and LCI1/20th r=-0.40 (p<0.01). The LCI demonstrated excellent within and good between visit repeatability for both a 1/40th and 1/20th washout (intraclass correlation coefficient (ICC)≥0.80). There was a statistically significant strong correlation between LCI1/40th and a shortened LCI1/20 of 0.86 (p<0.01). CONCLUSIONS: The LCI is repeatable within and between visits. There are weak correlations with measures of spirometry. A shortened LCI1/20th starting concentration correlates highly with a 1/40th washout, which may encourage clinical use.

COPD assessment test for the evaluation of COVID-19 symptoms.

There is evidence to demonstrate the ongoing symptoms of COVID-19; however, there are currently no agreed outcomes to assess these symptoms. This study examined the use of the chronic obstructive pulmonary disease (COPD) assessment test (CAT) for patients recovering from COVID-19. 131 patients who were admitted with COVID-19 were followed up over the phone to assess symptoms. The median (IQR) CAT score was 10 (5-16). Cough, phlegm and chest tightness domains were within range for healthy people, but there was evidence of significant breathlessness, loss of energy, and activity and sleep disturbance. The CAT is a useful tool to assess symptoms of COVID-19 recovery.