Introduction: SAD is a precursor and key feature of chronic obstructive pulmonary disease (COPD). The lower limit of normal (LLN) and fixed ratio definition of FEV1/FVC may be discordant in up to 54% of cases, where there is potential for COPD misdiagnosis(1). Therefore, there is a clinical need to assess SAD in older people and determine whether this is pathological or part of normal aging. Methods: Healthy controls (n = 29) and mild to moderate COPD patients over 60 years old underwent lung function once within a prospective cohort study SAFFRON (IRAS ID 253739). COPD patients were classified as discordant (FEV1/FVC >LLN; disCOPD; n =14) or concordant (FEV1/FVC <LLN; conCOPD; n = 21). Analysis: one-way ANOVA or Kruskall-Wallis for parametric and non-parametric data respectively, categorical data using chi-squared test. Results: ConCOPD patients were younger (p=0.002) with mean TLco and Kco <80%pred (both p<0.001) and elevated TLC and FRC (both p=0.001) implying that emphysema and hyperinflation are confined to this group. Established SAD markers were more aberrant in COPD v health, with lower FEV1/FVC, lower MMEF25-75, raised X5Hz on impulse oscillometry and raised R5-19 on Forced Oscillation Technique (all p≤0.04). Notably disCOPD exhibited differences in oscillometry from health, and higher LCI (p=0.005). Discussion: There is no evidence of emphysema or hyperinflation on lung function in disCOPD patients, despite the presence of SAD, highlighting the potential for misdiagnosis of early COPD due to silent SAD. Radiology, blood biomarker and functional capacity data, collected as part of the SAFFRON study, will be of benefit. Ref 1: 10.1136/thx.2008.098483

Background The most recent International Society for Heart Lung Transplantation (ISHLT) guidelines defines a maximal cardiopulmonary exercise test (CPET) as a respiratory exchange ratio (RER) of >1.05 with the achievement of anaerobic threshold (Mehra et al., 2016). Based off a maximal CPET, the ISHLT recommend a peak oxygen consumption (VO2peak) of ≤14 ml/min/kg for patient’s intolerant of beta-blockers and ≤12 ml/min/kg in the presence of a beta-blocker for guiding heart transplantation listing. Recently, Thomas and Sylvester (2020) demonstrated that a RER of 1.05 underestimated peak VO2peak and would impact patients’ risk stratification for surgery, or diagnostic outcomes. It is unknown whether this is true for patients with advanced heart failure referred for heart transplantation assessments. Methods A retrospective analysis of patients with advanced heart failure that underwent a CPET as part of their heart transplant assessment between May 2019 and July 2021 was performed via cycle ergometry. Patients were included if they met all of the following: symptom-limited test, peak RER >1.15 and >6-minute test duration. Oxygen consumption (VO2), minute ventilation and heart rate were collected at RER’s of 1.00, 1.05, 1.10, 1.15, 1.20 and peak-exercise. A Friedman test was used to compare data across all RER points, while independent t-tests were used to compare differences in data between specific RER’s. Results A CPET was performed in 151 patients, of which 59 patients met the inclusion criteria. Baseline characteristics can be seen in Table 1. VO2 (ml/min/kg) significantly increased as RER increased from 1.05 to peak (p<0.001) (Figure 1). Based on ISHLT guidelines for using VO2peak to guide heart transplantation listing, inappropriate referrals for heart transplantation would have occurred in 5%, 26%, 29% and 31% of patients when taking VO2 at an RER of 1.05 compared to 1.10, 1.15, 1.20 and peak RER, respectively. Conclusion In our cohort of patients with advanced heart failure, VO2peak progressively increased in parallel to RER from 1.05 to peak. Using an RER of 1.05 to determine a maximal CPET in patients referred for heart transplantation will underestimate true peak VO2peak in a proportion of cases and may lead to inappropriate heart transplantation referrals. Conflict of Interest None

Intro: Numerous centres are publishing pulmonary function testing (PFT) in patients after COVID-19. The initial publications showed a reduction in TLco that was more frequently reduced in severe disease and restrictive pattern to PFTs (Mo et al 2020). Aim: To investigate the impact of COVID-19 disease severity, as per WHO interrim guidance, on PFTs. Methods: PubMed and Embase were searched for studies including PFT data in patients who have recovered from COVID-19. To be included in the analysis the FEV1, FVC, TLco and/or TLC data needed to be stratified by severity (mild, moderate, and severe) and presented as frequency below the lower limit of normal (LLN) or <80% predicted. Frequency distribution for each severity was compared by Chi-Squared test, weighted averages are presented as mean (SD). Results: 2288 records were found; 24 papers measured PFT after recovery from COVID-19, and 9 of those presented data separated by severity and vs LLN or <80% predicted. Figure 1. Weighted averages for % of patients with PFT values <LLN or 80% predicted. Conclusion: Diffusing capacity abnormality is most abundant in patients who had severe COVID-19, commonly associated with a restrictive pattern.

Intro A recent ERS statement on standardisation of cardiopulmonary exercise testing (CPET) in chronic lung diseases (Radtke et al 2019) discussed the criteria for determining maximal effort. A CPET with a respiratory exchange ratio (RER) >1.05 is considered maximal using these criteria; V'O2 <85% predicted, V'E >85% predicted, and HR <90% predicted were considered abnormal responses if the test is maximal. We hypothesise that using an RER >1.05 as maximal will result in misinterpretation. Methods Retrospective analysis of CPETs performed at Birmingham Heartlands Hospital in 2019. Inclusion criteria: patient limited, RER >1.15 at peak, >6 mins. Exclusion criteria: highly variable RER indicating dysfunctional breathing. V'O2, V'E, and HR were measured at RERs of 1.05, 1.15 and peak, and were compared with Friedman tests. Results CPET was performed in 422 patients. 199 had an RER > 1.15 at peak. 23 patients were excluded due to dysfunctional breathing. The indication for testing was pre-operative assessment in 117 patients and CPET was for diagnostic purposes in 59 patients. Mean (SD) age = 61.4 (16.9) years, BMI = 27.7 (5.4), CPET duration 9.4 (1.8) mins; gender (F:M) 50:126. Of the 59 patients that were investigated for cause of breathlessness, 37% were normal at peak exertion based on the ERS criteria for abnormality. At an RER of 1.05 this was 3.4% and at an RER of 1.15 this was 25.4%. Of the 117 preoperative assessments, 88 had a V'O2peak >15 ml/min/kg and could be considered low risk for surgical intervention. At an RER of 1.05, 70% of these patients would have been considered high risk; 30% would have been considered high risk at RER 1.15. Discussion Using an RER of 1.05 an indicator of maximal effort underestimates some patients' true exercise capacity. This will have an impact on diagnosis and risk stratification.

In people recovering from COVID-19, there is concern regarding potential long-term pulmonary sequelae and associated impairment of functional capacity. Data published thus far indicate that spirometric indices appear to be generally well preserved, but that a defect in diffusing capacity (DLco) is a prevalent abnormality identified on follow-up lung function; present in 20-30% of those with mild to moderate disease and 60% in those with severe disease. Reductions in total lung capacity were commonly reported. Functional capacity is also often impaired, with data now starting to emerge detailing walk test and cardiopulmonary exercise test outcome at follow-up. In this review, we evaluate the published evidence in this area, to summarise the impact of COVID-19 infection on pulmonary function and relate this to the clinico-radiological findings and disease severity.

BACKGROUND:Healthcare practice in the UK has moved away from using aldehyde disinfectants for the decontamination of endoscopes, in part due to the risk of respiratory sensitization. Peracetic acid (PAA) in combination with hydrogen peroxide (HP) is a commonly used alternative.AIM:We describe a case of occupational asthma (OA) diagnosed at our specialist occupational lung disease clinic and caused by occupational exposure to PAA-HP mixture, used as a disinfectant in an endoscope washer-disinfector machine.CASE REPORT:A 48-year-old man employed as a mycologist and environmental microbiologist at a Birmingham city hospital, UK, presented following an acute exposure to PAA-HP mixture causing lacrimation, burning optic pain and headache. He had also experienced symptoms suggestive of OA for the preceding 10 months, and the diagnosis was confirmed through OASYS analysis of serial peak expiratory flow measurements. He had been exposed to PAA-HP mixture whilst working in the endoscopy department for 12 months prior to the acute episode, and a subsequent specific inhalation challenge test was positive with a late asthmatic response to PAA-HP mixture.CONCLUSION:This case provides evidence for a sensitization mechanism in OA caused by PAA-HP mixture.