Discussion:
This is an observational study evaluating the respiratory sequelae
following COVID-19 infection in Thai healthy children aged 7-18 years.
The main findings of our study revealed that a quarter of the patients
had at least one post COVID symptom which significantly associated with
the history of COVID-19 pneumonia. Pulmonary function impairment was
found in almost one-fifth of the patients and the obstructive impairment
was the most common. However, no clinical characteristics were
identified as a significant factor associated with the presence of
pulmonary function impairment and changes in pulmonary function
measures.
The prevalence of post COVID-19 symptoms in our study is consistent with
previous literatures which ranged between
23-27%12,13,14. In addition, fatigue, dyspnea and
cough are common symptoms in our study and consistent with findings in
other studies14,15. These outcomes are likely to
indicate that post COVID-19 symptoms are comparable across countries
despite variations in management; and after recovering from COVID-19
infection ongoing follow-up for the patients is necessary despite their
lack of remarkable medical backgrounds.
Pneumonia which represents the moderate severity of acute COVID-19
infection, was the only factor associated with respiratory sequalae.
Approximately, half of our patients with COVID-19 pneumonia had at least
one post COVID-19 symptom. This finding consolidates previous evidence
that patients suffering more severe infections or requiring intensive
care, are more susceptible to post COVID-19 symptoms, ranging from
30-70%13,15,16,17. This could be straightforwardly
explained by infection-related and cytokine-induced airway and lung
damage15,16. Therefore, children who have been
diagnosed with COVID-19 pneumonia are at a higher risk and in needs of
careful follow-up evaluation. The additional evaluation should include
both clinical review and pulmonary function tests.
Among the participants, almost one-fifth exhibited impaired pulmonary
function, with obstructive impairment being the most prevalent, followed
by possible restrictive impairment. Our findings aligned with existing
studies which reported impaired pulmonary function in the patients from
0-24%7,14,16,18,19,20. The wide range of the
prevalence of impaired pulmonary function after COVID-19 infection could
be explained by multiple reasons, for example children’s medical
backgrounds and the timepoint of pulmonary function assessment. In the
previous study Palacios et al study, it was found that children who had
pre-existing conditions such as asthma and obesity exhibited a higher
incidence of pulmonary abnormalities7. They also
reported that the rate of abnormal pulmonary function declined from 24%
to 10% over a nine-month follow-up period, which could be a result of
either natural healing process or the use of inhaled corticosteroids to
treat bronchial hyperresponsiveness7.
Our research revealed no significant correlation between post COVID
symptoms or COVID-19 pneumonia and impaired pulmonary function,
corresponding with earlier research16. Nevertheless,
around 15% of the participants who were diagnosed with COVID-19 URI and
did not exhibit persistent symptoms after the infection showed abnormal
spirometry results, mainly compatible with obstructive impairments.
Probably, this is a consequence of chronic subclinical inflammation of
peripheral airways caused by COVID-19, regardless of infection
severity21,22. These findings highlight the importance
of undertaking pulmonary function tests in patients with COVID-19
infection to evaluate their post-infection progression.
Although this study provides additional data and highlights the
importance of monitoring pediatric patients after COVID-19 infection,
there are some limitations. First and foremost, the sample size was
small as this study was undertaken in a single center. For assessing the
respiratory sequalae, we relied on clinical review and spirometry and
did not include computed tomography chest imaging, so we were unable to
address lung parenchymal changes such as pulmonary fibrosis. Moreover,
lung volume and diffusion capacity of the lungs were not routinely
measured, so we could not provide additional data on other functional
consequences of COVID-19 infection. Finally, this is a cross-sectional
study without ongoing evaluations for both post COVID-19 symptoms and
pulmonary function. We cannot ascertain whether the respiratory sequalae
persist over time or resolve spontaneously. Henceforth, further studies
are warranted to fill the gaps and improve the understanding of post
COVID conditions in children.