Spontaneous Evolution of COVID-19 Lung Sequelae: Results from a Double-Step Follow-Up

Abstract

Background: Few studies have reported a double-step follow-up of patients after hospitalization for COVID-19.

Objectives: We designed an observational double-step follow-up study with a clinical, functional, and radiological evaluation at 2 and 6 months after COVID-19. The primary outcome was to describe symptoms, spirometry, and 6-minute walking test (6MWT) at 2 and 6 months. Secondary outcomes were to identify if the lowest PaO2/FiO2 during hospitalization is related with functional and radiological evolution and to assess the correlation between radiological and functional abnormalities at 6 months.

Methods: Symptoms, spirometry, and 6MWT were assessed at 2 and 6 months; arterial blood gas, chest x-ray, and lung ultrasound were performed at 2 months; body plethysmography, diffusing capacity for carbon monoxide (DLCO), and CT scan were performed at 6 months.

Results: Sixty-four per cent and 42% of patients reported at least one symptom at 2 and 6 months, respectively. The most common 6-month functional alteration was DLCO impairment (57% of patients). An improvement of FEV1, FVC, and 6MWT was observed between 2 and 6 months (p < 0.001). Patients with PaO2/FiO2 <200 during hospitalization performed worse at 6MWT at 2 and 6 months (p < 0.05) and reported more extended radiological abnormalities at 6 months (p < 0.001) compared with patients with PaO2/FiO2>200. At 6 months, more extended radiological abnormalities were related with worse 6MWT, DLCO, and total lung capacity (p < 0.05).

Discussion: DLCO and 6MWT impairment seem to be the functional hallmark of COVID-19 and are related with the severity of acute pneumonia. At 6 months, radiological abnormalities were related to functional impairment.

Keywords: COVID-19; Follow-up; Pneumonia; Respiratory infection; Sequelae..

Fig. 1

Flow chart of the study.

Fig. 2

a6-months severity mMRC scale of dyspnoea.b6-months–severity DLCO (normal, mild, and moderate impairment).c6-months 6MWD over/under 80 per cent predicted.dComparison between 2-months 6MWD and 6-months 6MWD.eCharacteristics of HRCT during hospitalization and at 6 months.fComparison between extension score HRCT during hospitalization and 6-months HRCT.gCorrelation between extension score HRCT during hospitalization and 6-months 6MWT SpO₂ Nadir. mMRC, Modified British Medical Research Council Questionnaire.