Lung Function Impairments in COVID-19 Survivors Who Received Mechanical Ventilation

A high prevalence of lung function and functional impairments, along with a considerable symptom burden, has been reported among survivors of COVID-19 who required the use of mechanical ventilation (MV). Researchers of an observational study examined the clinical data that had been obtained prospectively for routine care. Results of the analysis were published in the Annals of the American Thoracic Society.

The investigators sought to establish whether short-term sequelae among patients who had received MV during hospitalization for COVID-19 would include physiologic, radiographic, and exercise impairment, in addition to a high symptom burden. All eligible patients had been laboratory-confirmed swab-positive for COVID-19; had received MV for 72 hours or longer at the Royal Brompton Hospital Adult Intensive Care Unit in London, United Kingdom; and had been discharged to a rehabilitation facility or to home. Hospital admission dates were between March 13, 2020, and May 21, 2020. Patients were discharged from the hospital between March 30, 2020, and July 20, 2020.

Among the 52 individuals who met the study inclusion criteria, 50 attended a multidisciplinary clinic at 6 weeks’ postdischarge. At this center, spirometry, diffusing capacity, and chest radiography were performed. The 6-minute step test (6MST) was used to evaluate physical functioning and exercise-induced oxygen desaturation. Patients’ self-reported symptoms and information from validated questionnaires were obtained to evaluate overall change from discharge, respiratory disability, breathlessness, health-related quality of life, anxiety, depression, posttraumatic stress, and cognition.

Overall, 80% of the patients were men, and the median age was 54.5 years. The median duration of MV was 15.5 days (range, 12-20 days). The median length of stay (LOS) in the hospital was 38 days (range, 28-51 days). Among the patients, 24% received extracorporeal membrane oxygenation (ECMO) and prone positioning was carried out in 60%. Intravenous corticosteroids were administered to 34% of the patients, with 42% of the patients having radiologically confirmed thromboembolic disease during hospitalization.

The lung function results of 47 patients were documented. Abnormal results were defined as below the lower limit of normal (standardized residual [SR] threshold of

< -1.645). Study results showed that all of the patients had abnormally low diffusing capacity of carbon monoxide (DL_co), 55% had low transfer coefficient for carbon monoxide, 44% had low forced vital capacity (FVC), and 28% had low forced expiratory volume in 1 second (FEV₁).

LOS and MV were significantly associated with FVC SR (P <.001 for both). Moreover, LOS and MV were also significantly associated with DL_co SR (P =.007 and P =.027, respectively). Although follow-up radiography revealed improvements in 90% of the patients, residual radiographic abnormalities were still present in 64%. Those patients who had an abnormal chest radiograph had significantly lower mean FCV (P =.025), lower mean 6MST (P =.005), and higher median Medical Research Council dyspnea score (P =.020), compared with those with a normal chest radiograph.

No significant differences were reported in lung function parameters or abnormal chest radiographs between patients who did vs those who did not receive ECMO, nor between those who did or did not develop secondary bacterial pneumonia. Additionally, radiologically confirmed pulmonary embolism (PE) was associated with a significantly decreased mean FVC SR (P =.022) and DL_co SR (P =.029), compared with those patients without PE.

Overall, 45 patients completed the 6MST. Based on the results, exercise-induced oxygen desaturation was observed in 9% (4 of 45) of these individuals. In fact, 98% of the patient cohort had a 6MST result that was below the 95% confidence interval.

The investigators concluded that detailed longitudinal studies are warranted to document the recovery course in this group of individuals following COVID-19 infection.

Reference

Finney LJ, Doughty R, Lovage S, et al. Lung function deficits and symptom burden in survivors of COVID-19 requiring mechanical ventilation.  Ann Am Thorac Soc.  Published online March 26, 2021. doi:10.1513/AnnalsATS.202102-099RL