Pulmonary Sequelae at 4 Months After COVID-19 Infection: A Single-Centre Experience of a COVID Follow-Up Service

Abstract

Introduction: At the end of the first year of the COVID-19 pandemic, more than 78 million known survivors were recorded. The long-term pulmonary sequelae of COVID-19 remain unknown.

Methods: We performed a retrospective analysis of a post-COVID follow-up service to estimate the burden of persistent pulmonary morbidity in hospitalised COVID survivors.

Results: A total of 221 patients were followed-up: 44 intensive care unit (ICU) and 177 ward patients. Further investigations were planned as per British Thoracic Society Guidelines: For all ICU patients (n = 44) and for 38 of 177 (21%) ward-based patients who had persistent symptoms and/or persistent radiographic changes on CXR at their initial 8-week follow-up visit. In the ward-based cohort, statistically significant associations with persistent symptoms were being an ex- or current smoker, having pre-existing diabetes, and having a longer length of stay. In patients requiring further investigations, pulmonary function tests (PFTs; n = 67) at an average of 15 weeks post-discharge showed abnormalities in at least one PFT parameter in 79% (equating to 24% of the entire cohort). The most common abnormality was an abnormal diffusion capacity of carbon monoxide (TLCO), highest in the ICU cohort (64% ICU vs. 38% non-ICU). TLCO correlated negatively with length of stay and with maximum inspired FiO₂ in the patient group as a whole. In ICU patients, TLCO correlated negatively with maximum inspired positive airway pressure. Computed tomography scans (n = 72) at an average of 18 weeks post-discharge showed evidence of persistent ground glass opacities in 44% and fibrosis in 21% (equating to 7% of the entire cohort).

Conclusion: Our data add to the growing evidence that there will be pulmonary sequelae in a proportion of COVID survivors, providing some insight into what may become a significant chronic global health problem.

Keywords: COVID-19; Coronavirus; Pulmonary function tests; Pulmonary sequelae; Radiological fibrosis.

Fig. 1

The proportion of patients with abnormal pulmonary function tests comparing ICU and non-ICU cohorts. Abnormal pulmonary function tests (PFT) are defined as < 80% predicted value for FEV1, FVC, and TLCO. Comparison is made between intensive care unit (ICU) patients and those non-ICU patients who required follow-up investigations. Not all PFTs were completed for all patients. The number of patients completing each test is shown under the appropriate bars. Statistical significance is measured using Fisher’s exact test and a p value of < 0.05 is denoted as statistically significant. NS not significant, FEV1 forced expiratory volume in 1 s, FVC forced vital capacity, TLCO diffusion capacity for carbon monoxide

Fig. 2

Percentage of predicted TLCO correlates negatively with increasing length of stay, increasing maximum FiO₂ and peak inspiratory positive airway pressure (IPAP). a Percentage of predicted TLCO compared with length of stay for all patients. b Percentage of predicted TLCO compared with length of stay for intensive care unit (ICU) patients. c Percentage of predicted TLCO compared with maximum inspired FiO₂ for all patients. d Peak IPAP correlates with percentage predicted TLCO in ventilated patients on ICU. Correlation is tested using Spearman’s correlation coefficient, and a p value of < 0.05 is denoted as statistically significant. TLCO diffusion capacity for carbon monoxide

Fig. 3

Radiological findings on CT Thorax at an average of 5 months after admission. a Prevalence of ground glass changes (GGO) and fibrotic changes on CT thorax at follow up. Comparison is made between intensive care unit (ICU) patients and those non-ICU patients who required follow-up investigations. These changes were significantly increased in intensive care unit (ICU) patients as compared to non-ICU patients (chi-squared test). b Prevalence of abnormalities in TLCO (< 80% predicted value) in each of the three radiological groups. These were significantly increased in those with ground glass changes and fibrotic change as compared to those with normal appearance on CT. Statistical significance is measured using the chi-squared test and a p value of < 0.05 is denoted as statistically significant