Dyspnoea in patients presenting to post-COVID respiratory clinic not fully explained by lung function impairment and chest radiography abnormalities.

Sir, Respiratory symptoms such as persistent dyspnoea are important reasons for post-COVID symptomatology.[1] We did a retrospective study on patients recovering from acute COVID-19 illness, seeking health care for persistent respiratory symptoms, in a specifically set up post-COVID respiratory (PCR) clinic. We analysed patients who attended the PCR clinic between September 2020 and March 2021. The symptomatology and other laboratory details when the patient presented to the PCR clinic were carefully recorded and this was retrieved. The clinical and relevant laboratory information during the acute COVID-19 illness were retrieved from the hospital electronic medical records and the disease severity was classified as per the WHO document of May 2020.[2] Chest X-rays were scored based on two scoring systems. The first was described by Yasin R et al.[3] for COVID-19 patients, derived from a study by Warren et al.[4] in patients with ARDS. The second was the Radiographic Assessment of Lung Oedema score, which was initially described by Warren et al.[5] and used in COVID-19 patients.[6,7] Pulmonary function test (PFT) was done at least 1 month after the point of COVID-19 diagnosis, adopting recommended safety protocol for testing during COVID times.[8] Six-minute walking test (6-MWT) was performed on room air by respiratory therapists according to American Thoracic Society guidelines.[9] For analysis, percentage of predicted values were taken for PFT and absolute walk distance was taken for 6-MWT. This study was approved by the Institutional Review Board (IRB Min No 13963 dated: 28/04/2021). Data were analysed using IBM compatible computer with SPSS version 21 (License number [Customer ID]: 200699; Vendor: SPSS South Asia Pvt Ltd. Bangalore). The PCR clinic visit occurred after a median of 6 weeks (range: 3–24 weeks), after the diagnosis. Males constituted 63% of the patients. The WHO severity grade of the acute COVID-19 was mild in 37%, moderate in 18%, severe in 38% and critical in 7%. The common symptoms during acute COVID-19 illness were dyspnoea (62%), cough (47%) and fever (46%). During the PCR clinic consultation, the common symptoms were dyspnoea (55%) and cough (26%). Univariate analysis was performed to compare clinical, radiologic and lung function parameters between patients with and without dyspnoea [Table 1]. There was no difference in lung function parameters FVC, FEV1, DLCO, 6-min walk distance and chest X-ray scores between those who had dyspnoea on follow-up those who did not have dyspnoea. More patients who presented with dyspnoea to PCR clinic also had dyspnoea during the COVID-19 illness (78.2% vs. 42.2%; P value = <0.001) and had moderate disease (25.5% vs. 8.9%; P value = 0.032) compared to those who did not present with dyspnoea. On the other hand, more patients without dyspnoea had mild disease compared with those without dyspnoea (23.6% vs. 55.5%; P value = 0.002). In our cohort, those with dyspnoea did not have worse lung function than those without, suggesting perhaps that factors other than lung function impairment may be responsible for the dyspnoea.Table 1: Univariate analysis of characteristics of patients with or without dyspnoea at follow-upIn a study by Rinaldo RF, 52% patients reported dyspnoea during their daily activity 3 months after any severity of COVID-19.[10] In this study, the lung abnormalities based on computerized tomography scan (CT) of thorax and pulmonary function parameter (FVC, TLC, DLCO) did not have any relation to the exercise capacity. Reduction in exercise capacity may be perceived as dyspnoea by some patients although this may not always be related. With cardiopulmonary exercise testing (CPET), they found that there is reduced anaerobic threshold in those with reduced exercise capacity suggesting that deconditioning plays a major role. Ong et al.[11] found that pulmonary function defects were detected in half of the recovered severe acute respiratory syndrome patients 3 months after hospital discharge, but the impairment was mild in almost all cases. Many patients had reduced exercise capacity as measured by CPET that cannot be accounted for by impairment of pulmonary function. In a cross-sectional study by Beaudry et al.,[12] persistent dyspnoea after COVID-19 was not associated with overt cardiopulmonary impairment or exercise intolerance. SARS-CoV-2 virus could have a direct effect on the skeletal muscles, which causes an impaired oxygen extraction.[13] Also, prolonged immobilization either due to hospitalization or home isolation aggravates the deconditioning. Corticosteroid myopathy and critical illness neuropathy can contribute in those with severe illness.[11] This knowledge brings to the fore the importance of early mobilization and rehabilitation during and after COVID-19 illness. Post-acute phase, a comprehensive 3-week pulmonary rehabilitation programme of those with mild/moderate and severe/critical COVID-19 illness, resulted in significant improvement in 6-min walk distance and FVC.[14] In patients with respiratory failure in intensive care unit, the earlier the rehabilitation is started, the better the improvement in 6-min walk distance.[15] Risk factors associated with persistent dyspnoea at 7 months in the study by Fernández-de-las-Peñas et al. included female gender, number of pre-existing comorbidities and number of symptoms at hospitalization and number days hospitalized.[16] In our study, we did not find any association of dyspnoea with age, gender or pre-existing chronic lung disease. The limitations of this study include its retrospective nature. There may be sicker patients or patients who would have recovered well who did not come to our clinic. We also did not quantify the dyspnoea and those with higher dyspnoea might have had lung function impairment. A prospective study with larger numbers with objective quantification of the symptoms and evaluation of systemic causes for breathlessness like anaemia and cardiac evaluation would be helpful. This study confirms that patients who have recovered from COVID-19 continue to have significant respiratory symptoms. Dyspnoea in such patients may not be correlated with lung function or radiographic abnormalities. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.