24-Month assessment of respiratory function in patients hospitalized for severe SARS-CoV-2 pneumonia: a follow-up study

Long COVID affects multiple body systems, with the respiratory system being particularly vulnerable. This study aimed to analyze the lung ventilatory function and diffusion capacity of patients with severe SARS-CoV-2 pneumonia during a 24-month follow-up course. Ventilatory function and lung diffusion capacity were assessed 6, 12, 18, and 24 months after hospital discharge. Ventilatory parameters, Diffusion Lung Carbon Monoxide (DLCO), and KCO (Carbon Monoxide transfer coefficient) normalization were defined as achieving values > 80% predicted. A total of 222 patients admitted to the Intensive Care Unit (ICU) at ASST Spedali Civili di Brescia, Brescia, Italy, were enrolled. Among the 172 patients who completed the study, 140 (63%) achieved normalization of ventilatory parameters, DLCO, and KCO. The median time to recovery was 4.5 months, and the hazard ratio (HR) decreased by 2% for each year of age increase. The median time to normalize ventilatory parameters (VC, FVC, FEV1, FEV1/FVC, TLC, and KCO) was 1.5 months, while the median time to alveolar volume (VA) normalization was 4.5 months. Male gender reduces the odds of normalization for FEV1/FVC and VA. The median time to DLCO normalization was 9 months, with HR reduced by 3.1% as each year of age increased and augmented by 226% in obese subjects. 24 months after severe COVID pneumonia, 14% of patients had persistent ventilatory and/or diffusive defects. Our study documented that male sex, age, and obesity impact the odds of normalization of ventilatory function and diffusive capacity. These findings underline the chronic nature of lung damage following severe COVID-19 pneumonia and the need for long-term follow-ups.