Key spirometric parameters for post-tuberculosis sequelae in patients after new coronavirus infection

The study evaluated key spirometric parameters in patients with post-tuberculosis (post-TB) lung sequelae after recovery from a new coronavirus infection. The main group incliuded 14 patients with clinically cured respiratory tuberculosis who had recovered from the new coronavirus infection and, after recovery, were sent to the Glukhovskaya tuberculosis sanatorium for treatment in 2020-2021. The control group included 52 patients with residual post-TB sequelae, who did not have a new coronavirus infection and who were treated at the sanatorium during the same period. The groups were comparable in terms of epidemiological and clinical criteria, except for post-TB sequelae: the main group included 13 cases (92.9%) of minor post-TB sequelae, 1 case (7.1%) of major post-TB sequelae, and the control group included 36 (69.2%) and 16 (30.8%) cases, respectively. Pulmonary function tests included vital capacity, forced vital capacity, forced expiratory volume in 1 second, and forced expiratory volume in 1 second/forced vital capacity. Tests were performed at admission to the sanatorium and after 1 month. At stage 1 in the main group, vital capacity, forced vital capacity and forced expiratory volume in 1 second were on average below the predicted level (>80%) compared with the control group, and after sanatorium treatment the same parameters improved slightly. In the control group, the initial indicators were significantly higher, the rates of recovery of vital capacity of the lungs and forced vital capacity of the lungs were comparable with the main group, during the 2nd examination, the average levels of recovery of vital capacity of the lungs and forced vital capacity of the lungs approached, and in terms of forced expiratory volume in the 1st second, they reached the norm. At baseline, low ventilatory lung capacity correlated with clinical symptoms, as 42.8% of patients in the main group and 55.7% of controls reported shortness of breath. However, after sanatorium treatment, the control group more often showed parameters below 60%: 7.7% of cases for vital capacity, 17.3% for forced vital capacity, 11.5% for forced expiratory volume in 1 second, while the main group showed mostly slight or moderate decrease of these parameters. Therefore, the new coronavirus infection has a negative impact on the functional capacity of the respiratory system, but major post-TB sequelae also contribute to the development of ventilatory disorders.