Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 59 11 2021 11 17 669 674 Akbar Soleymani Babadi Department of Pulmonary Diseases, School of Medicine, Shahrekord University of Medical Sciences, Shahrekord, Iran Alireza Kashefizadeh Shahid Dr Labbafinejad Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran Nooshin Dalili Department of Nephrology, Shahid Labbafinejad Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. AND Chronic Kidney Disease Research Center (CKDRC), Shahid Beheshti University of Medical Sciences, Tehran, Iran Laya Ohadi Shahid Beheshti University of Medical Sciences, Tehran, Iran Abbas Gheisoori Department of Internal Medicine, School of Medicine, Shahid Mostafa Khomaeini Hospital, Ilam University of Medical Sciences, Ilam, Iran. Hossein Kazemizadeh Advanced Thoracic Research Center, Tehran University of Medical Sciences, Tehran, Iran. 2021 07 03 2021 08 09 The most lethal adverse effect of COVID-19 is acute respiratory distress syndrome, which can lead to rapid death. This symptom even causes concern for patients who have recovered and have been discharged. Therefore, it is obligatory to test and monitor variations in their lungs’ function after recovery. In this study, we evaluated the pulmonary function of 64 patients with severe COVID-19, six weeks to 3 months after discharge. Pulmonary function parameters were measured by spirometry and body box according to the criteria of the American Thoracic Society and under the supervision of an adult pulmonologist. According to the forced expiratory volume (FEV1)/forced vital capacity (FVC) ratio and total lung capacity (TLC) values, it was found that 3.1% of people had an obstructive pattern, 40.63% of patients had the restrictive pattern, and 6.25% of improved individuals showed a mixed pattern. Furthermore, the study of diffusion capacity of carbon monoxide (DLCO) index revealed that 13.3%, 25%, and 53% of cases had mild, moderate, and severe disorders of gas exchange, respectively. In addition, determining the maximum amount of inspiratory muscles (PI max) and expiratory muscles (PE max) disclosed that the rate of these two indicators in 62.5% and 71.88% of the subjects were less than 50%, respectively. In general, the results of the present study suggest that pulmonary function test and follow-up of patients' condition are not only recommended but seems to be essential after recovery due to the large percentage of patients with the restricted pattern a few weeks after recovery.   https://acta.tums.ac.ir/index.php/acta/article/view/9512