In a recent study, Huang et al (1) described 6-month long-term health consequences of coronavirus disease 2019 (COVID-19) in Wuhan. Among patients requiring noninvasive ventilation, mechanical ventilation, and extracorporeal membrane oxygenation (ECMO), more problems in mobility, pain, and anxiety/depression were reported than in mild COVID-19 patients; however, no specific data on the most severe patients, that is, those on ECMO, have been described.
We collected data from two Belgian ICUs on COVID-19 patients treated with venovenous ECMO between March 10, and April 30, 2020. The study protocol was approved by the Institutional Hospital review boards (P2020/252 and OM020, Respiratory Functional Exploration-ECMO).
A total of 92 COVID-19 patients were admitted over the study period; of those, 32 (35%) required venovenous ECMO, and 11 of 32 (34%) survived at hospital discharge (median age 56 yr; 8/11 men; median body mass index 30.5 kg/m2). None of them had preexisting pulmonary or cardiac disease. All patients were treated with oral hydroxychloroquine (400 mg/d for 5 d), and only two patients received IV methylprednisolone (1 mg/kg for 7 d) after the second week since admission. The decision to initiate venovenous ECMO was based on the criteria from a recent randomized study (i.e., Pao2/Fio2 ratio < 80 for more than 6 hr or < 50 for 3 hr or pH < 7.25 and Paco2 > 60 mm Hg for more than 6 hr); the median pre-ECMO Pao2/Fio2 ratio was 60 (44–90,) and all patients had previously received muscle relaxants and several sessions of prone positioning. Duration of mechanical ventilation and ECMO therapy was 26 days (ranges, 17–50 d) and 15 days (8–36 d), respectively.
Among the 11 hospital survivors, all were still alive without oxygen requirement on January 31, 2021. Pulmonary function tests were obtained in nine patients after a median of 178 days (72–232 d) and 147 days (55–211 d) from ICU admission and ECMO weaning, respectively (Table 1, Supplemental Digital Content, http://links.lww.com/CCX/A720). The results of these tests showed a preserved median forced vital capacity (FVC, 83% of predicted value [51–99% of predicted value]) and forced expiratory volume in 1 second (82% of predicted value [60–99% of predicted value]). Pulmonary volumes were also within normal ranges, as the median residual volume and the median total lung capacity were 100% of predicted value (50–140% of predicted value) and 90% of predicted value (50–100% of predicted value), respectively. Only the diffusion capacity of the lung for carbon monoxide (DLCO) was decreased (median 58% of predicted value [37–95% of predicted value]). The 6-minute walking test (6MWT) was performed in six patients and resulted in a median of 468 meters (365–625 meters), corresponding to 68% of predicted value (57–90% of predicted value); the median pulsed oxygen saturation in ambient air before exercise was 97% (96–98%), which slightly decreased at the end of 6MWT to 92% (91–96%).
Together with recent studies showing persistence of radiological involvement (2) and abnormality of pulmonary function tests (3) in COVID-19 patients at hospital discharge, our data suggested that, in the most severe pulmonary involvement of COVID-19 requiring ECMO support, long-term diffusion disorders (i.e. 7/9 patients have DLCO < 80% of predicted) may persist without other remarkable abnormalities of their pulmonary function tests. These values are similar to those reported by Grasselli et al (4) in 18 patients treated with venovenous ECMO for other causes than COVID-19. The modest but still relevant limitation on the 6MWT may also suggest, with all the limitations of a test available only in six patients and the lack of pre-COVID assessment, that the diffusion pulmonary impairment could potentially compromise high-level physical efforts. The main limitations of this study are the lack of standardization for “long-term” assessment (i.e., which varied between 2.5 and 7.5 mo after the onset of COVID-19), of radiological (i.e., chest CT scan) evaluation, and of further appraisal (i.e., at 1 yr).
In this small retrospective study, patients with a successful recovery from COVID-19 after ECMO support presented modest alterations of long-term respiratory diffusion and physical capacities.
1. Huang C, Huang L, Wang Y, et al. 6-month consequences of COVID-19 in patients discharged from hospital: A cohort study. Lancet. 2021; 397:220–232
2. Wang Y, Dong C, Hu Y, et al. Temporal changes of CT findings in 90 patients with COVID-19 pneumonia: A longitudinal study. Radiology. 2020; 296:E55–E64
3. Mo X, Jian W, Su Z, et al. Abnormal pulmonary function in COVID-19 patients at time of hospital discharge. Eur Respir J. 2020; 55:2001217
4. Grasselli G, Scaravilli V, Tubiolo D, et al. Quality of life and lung function in survivors of extracorporeal membrane oxygenation for acute respiratory distress syndrome. Anesthesiology. 2019; 130:572–580