The COVID-19 pandemic, caused by infection with the virus known as SARS-CoV-2, has created a complex scenario for global health, with various types of complications and levels of functional impairment in millions of individuals recovering from the disease. The severe form of the disease causes lung damage and may result in respiratory failure. Subsequently, the affected patients may develop pulmonary fibrosis, a consequence of the process of lung injury repair. Patients presenting with more severe forms of the disease often need respiratory support, which ranges from oxygen therapy to prolonged invasive mechanical ventilation. Prolonged hospitalization of patients requiring intensive care may have severe systemic consequences.(1) Although post-COVID-19 sequelae are more common in patients who developed the severe form of the disease, individuals who had moderate disease may also have some degree of functional impairment, as may those who did not require hospitalization.
 
Post-COVID-19 functional impairment can limit the ability of the individual to perform activities of daily living, reduce functionality, alter professional performance, and hinder social interaction. In addition, the affected individuals can become more sedentary, increasing the risk of comorbidities. Today, although it is still imperative to take action to reduce the risk of mortality, health care facilities need to readjust their strategies to target the physical and functional recovery, as well as the social reintegration, of those individuals through pulmonary rehabilitation.
 
PULMONARY REHABILITATION AFTER COVID-19
 
In addition to the disease itself, prolonged hospitalization (with or without the use of mechanical ventilation) can have deleterious effects, such as pulmonary, cardiovascular, muscle, and cognitive changes, as well as anxiety and depression.(1) It is not uncommon for a prolonged ICU stay to lead to the development of ICU-acquired muscle weakness, which hinders physical and functional recovery.(2) Patients who recover from COVID-19 after a prolonged ICU stay should undergo pulmonary rehabilitation, initially in an individualized, gradual manner during hospitalization, and continuing after hospital discharge in order to mitigate/reverse the consequences of the disease.(3) Ideally, the pulmonary rehabilitation of such patients should be conducted by a multidisciplinary team because of the multisystemic impairment caused by COVID-19.
 
Although early mobilization is essential to the recovery of critically ill patients with COVID-19, many such patients show a rapid drop in oxygen saturation in the beginning of the recovery phase,(4) which limits early rehabilitation to some extent. However, other objectives must be considered during hospitalization, such as improving respiratory symptoms and maintaining airway permeability. Therefore, an early bedside approach, special attention being given to any signs of clinical instability of the patient, is recommended.
 
In patients who have recovered from COVID-19, the physical and functional impairment can persist for weeks after hospital discharge, as can some symptoms (such as dyspnea, desaturation, cough, weakness, and fatigue). In addition to the damage caused by prolonged hospitalization and inactivity, the persistent high inflammatory burden and previous health conditions seem to have a negative influence on the recovery of such patients.(3,5,6) A PaO2/FiO2 ratio < 324 and BMI ≥ 33 kg/m2 at hospital admission are independent predictors of persistent respiratory impairment and the need for follow-up.(5) To improve the evolution and, consequently, the prognosis of such patients, rehabilitation after discharge is also recommended, given that physical exercise is feasible and useful for survivors of critical illnesses.(7) Because there is as yet no large body of evidence on specific physical rehabilitation for COVID-19 survivors, it is recommended that low- to moderate-intensity exercises be prescribed, safety being a priority. The needs and the functional impairment of each individual must also be considered in the rehabilitation program.(3) Prior to hospital discharge, the need to use oxygen (at rest or during physical exertion) must also be evaluated.(3) Chart 1 describes some of the principles of rehabilitation for COVID-19 survivors.

 
HOME-BASED PULMONARY REHABILITATION
 
Given that SARS-CoV-2 continues to have a high rate of infection, physical distancing has still been strongly recommended. Physical distancing makes it practically impossible to carry out traditional outpatient rehabilitation in groups, and rehabilitation programs (including physical exercise programs) should therefore be adapted to be performed at home. The efficacy of home-based rehabilitation has been demonstrated in various studies, including some conducted in Brazil.(8) Patients who are more debilitated can also benefit from home-based rehabilitation because it allows them to avoid going to the outpatient clinic, which could hinder adherence to the program and increase the risk of reinfection. In addition, patients with severe post-COVID-19 sequelae often need help from family members, who can be trained by health professionals in their own home environment. Individualized rehabilitation of such patients and training of family members in the home environment allows the use of the resources available in each home, with the necessary adjustments, in an environment that is familiar to the patient. Finally, current technological tools (such as software and applications for tablets and cell phones) allow prescription, and remote monitoring of rehabilitation activities, providing greater safety for patients and family members.
 
TELEREHABILITATION
 
In an attempt to mitigate difficulties in the process of rehabilitating COVID-19 survivors and to reduce risks, greater attention has been given to telerehabilitation. Telerehabilitation uses telecommunication resources to offer rehabilitation remotely, in real time or not, the benefits of which are similar to those of face-to-face supervised rehabilitation,(9) thus minimizing barriers of distance, time, costs, and risks. The Brazilian Federal Council of Physiotherapy and Occupational Therapy, by means of Resolution no. 516 of March 20, 2020,(10) has authorized the teleconsultation, teleinterconsultation, and telemonitoring services that have already been endorsed by the World Health Organization. Chart 1 describes some principles of telerehabilitation in COVID-19 survivors.
 
FINAL CONSIDERATIONS
 
Pulmonary rehabilitation is recommended mainly to improve the physical and functional recovery of COVID-19 survivors before and after hospital discharge. Therefore, it is necessary to consider the needs of each patient carefully by performing a comprehensive assessment. Given the systemic manifestations of COVID-19, survivors should be monitored by a multidisciplinary team. There is as yet no robust body of evidence on the characteristics and effects of specific interventions for COVID-19 survivors. Therefore, current rehabilitation guidelines for that population are mainly based on preliminary results, expert opinions, and previous evidence on the rehabilitation of patients surviving critical illnesses.
 
FINANCIAL SUPPORT
 
AVS and ADF are recipients of grants from the  Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Office for the Advancement of Higher Education). FP is the recipient of a productivity grant from the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, National Council for Scientific and Technological Development).

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7. Denehy L, Skinner EH, Edbrooke L, Haines K, Warrillow S, Hawthorne G, et al. Exercise rehabilitation for patients with critical illness: a randomized controlled trial with 12 months of follow-up. Crit Care. 2013;17(4):R156. https://doi.org/10.1186/cc12835


8. Pradella CO, Belmonte GM, Maia MN, Delgado CS, Luise AP, Nascimento OA, et al. Home-Based Pulmonary Rehabilitation for Subjects With COPD: A Randomized Study. Respir Care. 2015;60(4):526-532. https://doi.org/10.4187/respcare.02994


9. Lundell S, Holmner Å, Rehn B, Nyberg A, Wadell K. Telehealthcare in COPD: a systematic review and meta-analysis on physical outcomes and dyspnea. Respir Med. 2015;109(1):11-26. https://doi.org/10.1016/j.rmed.2014.10.008


10. Brasil. Conselho Federal de Fisioterapia e Terapia Ocupacional (COFFITO) [homepage on the Internet]. Brasília: COFFITO; c2020 [cited 2020 Dec 28]. RESOLUÇÃO Nº 516, DE 20 DE MARÇO DE 2020 – Teleconsulta, Telemonitoramento e Teleconsultoria. Available from: https://www.coffito.gov.br/nsite/?p=15825


11. Wang TJ, Chau B, Lui M, Lam GT, Lin N, Humbert S. Physical Medicine and Rehabilitation and Pulmonary Rehabilitation for COVID-19. Am J Phys Med Rehabil. 2020;99(9):769-774. https://doi.org/10.1097/PHM.0000000000001505


12. Australia. NSW Government. Health [homepage on the Internet]. Sydney: NSW Government; c2021 [cited 2021 Jan 4]. Delivering pulmonary rehabilitation via telehealth during COVID-19. Available from: https://www.health.nsw.gov.au/Infectious/covid-19/communities-of-practice/Pages/guide-pulmonary-rehabilitation.aspx