key: cord-0895017-gw408d6p authors: Madrid-Mejía, Wilmer; Gochicoa-Rangel, Laura; Padilla, José Rogelio Pérez; Salles-Rojas, Antonio; González-Molina, Amaury; Salas-Escamilla, Isabel; Durán-Cuellar, Adela; Silva-Cerón, Mónica; Guzmán-Valderrábano, Carlos; Lozano-Martínez, Luis title: Improvement in Walking Distance Lags Raise in Lung Function in Post-COVID Patients date: 2021-05-14 journal: Arch Bronconeumol DOI: 10.1016/j.arbres.2021.04.027 sha: 332ea6073b3988d521e66620876103aadcedece4 doc_id: 895017 cord_uid: gw408d6p nan Germany). The 6-MWT was performed in a 30-m corridor using a pulse oximeter with a finger sensor (Massimo SET, Rad 57, Massimo, Irving, US). All PFT lab staff wore personal protective equipment; and each patient used disposable virus and bacterial filters. 16 Comparisons of variables between visits were performed with paired Student's t-tests, and categorical variables were compared with McNemar's test. The changes in each variable were evaluated by a one-sample t-tests against a hypothesized mean of zero. Models with multilevel analysis were used to identify predictors of improvement of the main outcome variables (forced lung volumes, DL CO , 6-MWT, SpO 2 nadir during the 6-MWT, MIP-MEP and clinical symptoms). The change in functional variables during follow-up was adjusted for follow-up time in months, which was not identical in all participants. Data capture was performed with RedCap ® , and data analysis with the STATA v.16 program. We invited 79 patients to participate; 70 attended the lab, 57% were men and 40 (57%) had received invasive mechanical ventilation (IMV). The mean age was 47.2 ± 13 years, mean weight 74.6 kg ± 3 and mean height 162 cm ± 8.5; 75% of participants were overweight or obese. The mean time elapsed between the onset of symptoms and the first and second visits was 92 ± 22 days and 174 ± 37 days, respectively. At the first visit, 7 subjects did not perform the 6-MWT due to a risk of falling, alterations in gait or dizziness; at the second visit, 2 individuals could not perform any study due to anxiety or cardiovascular decompensation, and 4 additional individuals could not perform the 6-MWT. Table 1 shows the increases in forced lung volumes, DL CO and MIP-MEP at the second evaluation. The mean changes per month of follow-up were as follows: FEV 1 : +23 ml (95%CI 3.2-43.2 p = 0.02), FVC: +45 ml (95%CI 20-70, p = 0.0006), and DL CO : +0.7 ml/min/mmHg (95%CI 0.35-1.1, p = 0.0002), and improvement among them was correlated. Although DL CO on average, increased significantly in the participants, in two patients decreased >15%. We observed no significant increase in the distance walked during the 6-MWT (6-MWD, +3.9 m, 95% CI −2.97 to 10.5, p = 0.26); moreover, 14 subjects walked 30 meters less than in the first evaluation, which is considered the minimum clinically significant difference. The change in the 6-MWD did not correlate with improvement in the other functional tests. In mixed models, the distance walked was associated with DL CO (1.99 m/unit, 95% CI −0.4 Desaturation (4% decrease from baseline or drop to <85%) during the 6-MWT was present in 65% of patients in the first evaluation and in 46% of patients in the second, with a nonsignificant quantitative change (−0.01%/month, p = 0.8), even if adjusted for meters walked (2%/km/month, p = 0.98). In mixed models, desaturation during the 6-MWT was associated with higher BMI (p = 0.056), lower DL CO (p < 0.03) and cough persistence (p = 0.02) but not with previous IMV (p = 0.17). IMV during acute infection was associated with a significant decrease in DL CO (2.5 ml/min/mmHg) and in the 6-MWT (41 m) (p = 0.02) but did not affect FEV 1 (p = 0.98), FVC (p = 0.21) or clinical symptoms. Surprisingly, almost half of subjects presented a slow heart rate recovery (HRR) one minute after finishing the 6-MWT, (HRR<14 beats per minute), especially in those who had IMV. We observed that at 6 months after presentation of COVID-19, respiratory mechanics had improved slightly (<100 ml per month of follow-up), the DL CO improved to a greater degree (0.7 U/month) and improvements in FEV 1 , FVC and DL CO were intercorrelated. However, no improvement was observed in the distance walked, or in the oxygen desaturation after the 6MWT as a crude value or adjusted by meters walked. There were even individuals in whom the 6-MWT decreased, even though they had participated in a rehabilitation program. This result could be due to physical deconditioning if individuals did not continue to exercise at home. Furthermore, these individuals may have important limitations that prevent increasing their exercise level, such as fatigue, weakness, mental health problems, or restriction in pulmonary circulation with or without pulmonary hypertension, which could partly explain the persistent oxygen desaturation. As shown in Table 1 , 46% of participants did not exhibit proper HRR within one minute of completing the 6-MWT. In previous studies, female sex, the presence of comorbidities, and recovering from acute respiratory distress syndrome were associated with lower 6-MWT scores. However, in our group, even individuals who did not require IMV demonstrated lack of improvement in the 6MWD with persisting oxygen desaturation, a common event at the altitude of Mexico City. 17 After a median of 78 days, odynophagia and anosmia improved, but other symptoms persisted, regardless of whether or not patients were intubated. These findings demonstrated the long convalescence period that can accompany COVID-19, similar to other infections such as SARS-CoV and MERS. [18] [19] [20] In conclusion, after 6 months of post-COVID follow-up, small improvements in FEV 1 and FVC and moderate improvements in DL CO were observed, but the walking distance did not improve substantially. Moreover, almost half of participants manifested oxygen desaturation and delayed HR recovery after walking regardless of whether they were intubated. The impact of physical deconditioning should be eliminated as much as possible, possibly through in situ massive rehabilitation programs, whereas other pulmonary or nonpulmonary factors that may limit physical conditioning should be excluded. W.M-M was involved in literature search, data collection, interpretation of data for the work, and revising the content. L.G.R contribute to the conception or design of the work; acquisition, analysis, interpretation of data, drafting the work, revising it critically for important intellectual content. J.P-P contribute to analysis, interpretation of data, revising it critically for important intellectual content. A.S-R was involved in literature search, data collection, data base elaboration and in the writing of the manuscript. A.G-M was involved in data collection, interpretation of data for the work, and revising the content. Functional characteristics of patients with SARS-CoV-2 pneumonia at 30 days post infection Lung ventilation function characteristics of survivors from severe COVID-19: a prospective study The pulmonary sequalae in discharged patients with COVID-19: a short-term observational study Abnormal pulmonary function in COVID-19 patients at time of hospital discharge Follow-up study of the pulmonary function and related physiological characteristics of COVID-19 survivors three months after recovery Persistence of COVID-19 symptoms after recovery in Mexican population Reduced diffusion capacity in COVID-19 survivors Follow up of patients with severe coronavirus disease 2019 (COVID-19): pulmonary and extrapulmonary disease sequelae Impact of coronavirus disease 2019 on pulmonary function in early convalescence phase 6-month consequences of COVID-19 in patients discharged from hospital: a cohort study Standardization of spirometry 2019 update. An Official American Thoracic Society and European Respiratory Society Technical Statement ERS/ATS standards for single-breath carbon monoxide uptake in the lung technical standard: field walking tests in chronic respiratory disease measurement properties of field walking tests in chronic respiratory disease ATS/ERS Statement on respiratory muscle testing Functional respiratory evaluation in the COVID-19 era: the role of pulmonary function test laboratories Prevalence of oxygen desaturation and use of oxygen at home in adults at sea level and at moderate altitude The 1-year impact of severe acute respiratory syndrome on pulmonary function, exercise capacity, and quality of life in a cohort of survivors The long-term impact of severe acute respiratory syndrome on pulmonary function, exercise capacity and health status Long-term bone and lung consequences associated with hospital-acquired severe acute respiratory syndrome: a 15-year follow-up from a prospective cohort study