EVALUATION OF FUNCTIONAL PARAMETERS OF RESPIRATORY SYSTEM IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE IN 6-MINUTE WALKING TEST

Aim. To study the functional parameters of the respiratory system of patients with COPD of different degree of severity in a 6-minute walking test (6MWT). Materials and Methods. The study was performed on 64 patients with COPD of different severity, with no exacerbations in the preceding 6 weeks. The criteria for non-inclusion of patients into the study were presence of other diseases that could affect the covered distance in 6-minute walk test. During walking, dynamic pulse oximetry was performed and changes of lung ventilation parameters were assessed on Spiropalm 6MWT (Cosmed, Italy). Results. In 6MWT, a high incidence of patients with desaturation (SpO2≥4%) (39%) was found among patients with COPD of different severity (I-IV). It was noted that in the group of ‘desaturators', SpO2 values were initially low. There was also noted an increase in the number of patients – ‘desaturators' with the degree of severity of COPD – from I-II degree (0%; 24%) to III-IV grade (40%; 36%). The difference in saturation (SpO2) between ‘nondesaturators' and ‘desaturators' was statistically significant: the SpO2 level before 6MWT was 94.38±2.45% and 92.48±3.33% (p<0.01), the average SpO2 level in 6MWT was 93.69±2.27% and 86.92±3.84% (p<0.001), the minimum SpO2 level in 6MWT was 92.85±2.33% and 83.72±5.38% (p<0.001), the level of SpO2 immediately after 6MWT was 94.1±2.26% and 86.4±4.72% (p<0.001). In 23.1% of cases, the lowest SpO2 values were noted immediately after 6MWT, but in 76.9% of cases they were recorded in 6MWT. Of importance is a correspondence between a drop in saturation on physical exertion and increase in the severity of obstructive disorders (FEV1) in the ‘desaturation' group. Conclusions. In 39% of patients with COPD of II-IV degree of severity, a ‘latent' desaturation (SpO2 ≥4%) was detected in 6MWT. A statistically significant decrease in FEV1 (p<0.001) was found in patients with ≥4% reduction of SpO2. To identify the lowest SpO2 values, saturation assessment in patients with COPD should be carried out throughout and upon completion of the test.