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Akter, et al.
consequently facilitating pneumonia and ARDS that can 6-minute walking test (6MWT) 4 months after hospital
cause irreversible lung damage in severe patients [10-14] . discharge. Lung ultrasound study findings indicate
Worsened long-term irreversible effects on recovered gradual absorption of peripherally distributed ground-
COVID-19 patients correlate with lung involvement in glass opacities, especially in the posterior and lower
the acute phase of infection and degree of underlying lung zones, after acute COVID-19 pneumonia [26] .
systemic inflammation [15,16] . Different follow-up studies have demonstrated
Unfortunately, around 80% of SARS-CoV-2 patients significant results indicating various long-term
have a different extent of lung damage and shortness complications in a recovered study population, whereas
of breath, indicating that recovering from the disease some have reported lung recovery in patients over time.
is not beneficial in achieving fully recovered lungs, A follow-up study lasting for 8 months, including 40
which, however, could lead to different respiratory tract- COVID-19 patients discharged from the hospitals, out
related problems after months to years. The long-term of which 25 individuals had severe clinical outcomes
existence of abnormal lung lesions has been proven while staying in hospital, illustrates the long-term impact
by chest computed tomography (CT) of the recovered of severe COVID-19. Severe patients still have physical
COVID-19 patients that showed residual lesions and/or psychological symptoms, a higher rate of abnormal
although the patients had been discharged from the diffusing capacity of the lung for carbon dioxide (DLCO),
hospital 6 months ago [17,18] . Patients with associated risk small airway dysfunction, and resistance in the peripheral
factors are mostly in danger of experiencing irreversible airways. The analysis demonstrates that severe patients
lung damage . Moreover, severe COVID-19 patients requiring longer oxygen treatment and with increased CT
[19]
stay in ICU for a longer period, and patients with pre- scores are at higher risk of abnormal DLCO, indicating
existing comorbidities are at the highest risk of getting long-term irreversible lung injury . Similarly, in another
[27]
post-COVID-19 sequelae of lung diseases, which could follow-up study, after 1 year of hospital discharge,
lead to advanced fibrosis, irrecoverable fibrosis, and lung patients experienced severe COVID-19 outcomes and
injury. Lung transplantation would benefit the survival had irreversible fibrotic interstitial lung abnormalities .
[28]
of severe patients; a few patients have undergone lung On the other hand, Chen et al. observed
transplantation due to COVID-19-mediated irreversible gradual improvement of around 47% of discharged
lung damage [20,21] . However, conventional lung COVID-19 patients with the help of CT score in a
transplantation still has multiple limitations that can be 1-year follow-up study, whereas elderly patients have
overcome by the three-dimensional (3D) bioprinted lung. shown the risk of long-term complications because of
unsatisfactory recovery since hospital discharge. Elderly
2. Post-COVID-19 sequelae of lung diseases patients who have been given steroids are also at risk
Based on the previous SARS-CoV and Middle East of long-term irreversible complications, whereas most
respiratory syndrome outbreaks, it has documented studies have observed recovery of patients from lung
that pulmonary involvement with functional and injury [29-31] . Post-infectious pulmonary fibrosis is another
radiological impairments would persist in recovered common finding in critically ill COVID-19 patients
patients after hospital discharge for months; these diagnosed with chest X-ray, presence of hypoxia,
patients were of older age, had been in the ICU or 6MWT [32] . Recalde-Zamacona et al. analyzed
for a longer period, and had higher peak lactate 10 critical COVID-19 patients with at least one
dehydrogenase (LDH) levels [22-24] . Knowing the comorbidity, and the histopathological findings match
interaction between previous viral cases of pneumonia with other studies where numerous features have been
and pulmonary involvement recovery from COVID- observed, including diffuse alveolar damage, type II
19-mediated organ damage is a matter of concern as pneumocyte hyperplasia, hypertrophy, and reactive
most of the recovered patients will make a complete atypia. Moreover, they detected small pulmonary artery
recovery, whereas others will experience a sequela long thrombosis, diffuse peripheral ground-glass opacities,
after COVID-19 recovery as they were being affected and air bronchogram [33-35] . According to another 6-month
with acute infection. The National Institute of Health follow-up study, more than half of the recovered patients
has renamed the constellation of symptoms from had at least one common sequela, and nearly 60% had
“long COVID” to post-acute sequelae of COVID-19 more than 1 symptom.
in December 2020 [25] . Numerous studies have found Another unusual complication observed recently
surprising details, for instance, COVID-19 survivors in recovered COVID-19 patients is lung cavitation.
developed pulmonary embolism de novo and 7.1% of A case report by Angirish and Parmar demonstrates
recovered individuals were diagnosed with pulmonary lung cavitation in a 51-year-old recovered patient by
hypertension. In addition, 48.8% of survivors still CT re-examination while the patient was negative for
have breathing difficulty and cannot perform a SARS-CoV-2, bronchoscopy, tuberculosis, and fungal

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