Pulmonary diffusing capacity for carbon monoxide and nitric oxide after COVID-19: A prospective cohort study (the SECURe study).

Many patients exhibit persistently reduced pulmonary diffusing capacity after coronavirus disease 2019 (COVID-19). In this study, dual test gas diffusing capacity for carbon monoxide and nitric oxide (DL,CO,NO) metrics and their relationship to disease severity and physical performance were examined in patients who previously had COVID-19. An initial cohort of 148 patients diagnosed with COVID-19 of all severities between March 2020 and March 2021 had a DL,CO,NO measurement performed using the single-breath method at 5.7 months follow-up. All patients with at least one abnormal DL,CO,NO metric (n = 87) were revaluated at 12.5 months follow-up. The DL,CO,NO was used to provide the pulmonary diffusing capacity for nitric oxide (DL,NO), the pulmonary diffusing capacity for carbon monoxide (DL,CO,5s), the alveolar-capillary membrane diffusing capacity and the pulmonary capillary blood volume. At both 5.7 and 12.5 months, physical performance was assessed using a 30 s sit-to-stand test and the 6 min walk test. Approximately 60% of patients exhibited a severity-dependent decline in at least one DL,CO,NO metric at 5.7 months follow-up. At 12.5 months, both DL,NO and DL,CO,5s had returned towards normal but still remained abnormal in two-thirds of the patients. Concurrently, improvements in physical performance were observed, but with no apparent relationship to any DL,CO,NO metric. The severity-dependent decline in DL,NO and DL,CO observed at 5.7 months after COVID-19 appears to be reduced consistently at 12.5 months follow-up in the majority of patients, despite marked improvements in physical performance.

Impact of a 12-week high-intensity interval training intervention on cardiac structure and function after COVID-19 at 12-month follow-up.

In patients previously hospitalised for COVID-19, a 12-week high-intensity interval training (HIIT) intervention has previously been shown to increase left ventricular mass (LVM) immediately after the intervention. In the present study, we examined the effects of the same HIIT scheme on LVM, pulmonary diffusing capacity, symptom severity and functional capacity at 12-month follow-up. In this investigator-blinded, randomised controlled trial, 12 weeks of a supervised HIIT scheme (4 × 4 min, three times a week) was compared to standard care (control) in patients recently discharged from hospital due to COVID-19. At inclusion and at 12-month follow-up, LVM was assessed by cardiac magnetic resonance imaging (cMRI, primary outcome), while pulmonary diffusing capacity for carbon monoxide (DLCOc, secondary outcome) was examined by the single-breath method. Symptom severity and functional status were examined by the Post-COVID-19 Functional Scale (PCFS) and King's Brief Interstitial Lung Disease (KBILD) questionnaire score. Of the 28 patients assessed at baseline, 22 completed cMRI at 12-month follow-up (12.4 ± 0.6 months after inclusion). LVM was maintained in the HIIT but not the standard care group, with a mean between-group difference of 9.68 [95% CI: 1.72, 17.64] g (P = 0.0182). There was no differences in change from baseline to 12-month follow-up between groups in DLCOc % predicted (-2.45 [-11.25, 6.34]%; P = 0.578). PCFS and KBILD improved similarly in the two groups. In individuals previously hospitalised for COVID-19, a 12-week supervised HIIT scheme resulted in a preserved LVM at 12-month follow-up but did not affect pulmonary diffusing capacity or symptom severity.