Objective: To investigate the patterns of pulmonary function in severe acute respiratory syndrome (SARS) patients during three-year convalescent period, and to investigate the changes and the medium and long term effects on pulmonary function of SARS patients.
Methods: Pulmonary function tests were conducted for four times in 37 SARS patients during three-year convalescent period. They were discharged from hospital within one month, three months, one year and three years respectively. At the same time, pulmonary function of 15 healthy persons was examined as controls to be used for comparison.
Results: Compared with the healthy controls, there were significant decrease in forced vital capacity (FVC), vital capacity (VC), one second forced expiratory volume (FEV1), 25%-75% forced expiratory flow (25%-75%FEF) of SARS patients within three years after their discharge from hospital (all P<0.05). There were no significant differences in FEV1/FVC, total lung capacity (TLC), diffusing capacity of the lung for carbon monoxide (DLCO) between the two groups (all P>0.05). Abnormality rate of DLCO in the SARS patients within three years after discharge was significantly decreased (32.4% vs. 5.4%,P<0.05), but no significant differences in FVC, VC, 25%-75%FEF among SARS patients discharged one month and three years from the hospital (all P>0.05). Ten SARS patients showed lower FVC (mild degree in 9 cases, severe degree in 1 case) three years later, 2 patients showed mildly lowered DLCO.
Conclusion: The lung diffusion function of the SARS patients had recovered after they were discharged from hospital within three years, but in 20%-30% patients there is still mild or moderate restrictive ventilation function abnormality and small airway function impairment. The lung functions of most patients have recovered gradually, but in a minority of patients they may be impaired.