Prognostic role of results of dynamic capnography in integral assessment of parameters of respiratory system in 6-minute walk test in patients with chronic heart failure

Aim. To study the prognostic value of the results of dynamic capnography in the complex assessment of parameters of the respiratory system in 6-minute walk test in patients with chronic heart failure (CHF).

Materials and Methods. 73 Patients were examined: the group of study included 48 patients with IIA or IIB stage CHF (mean age 57.9±4.6 years, 23 men), the control group included 25 practically healthy volunteers (mean age 47.6±3.5 years, 9 men). The patients were conducted complex determination of parameters of the respiratory system: clinical scaling before and after 6-minute walk test (6MWT), instrumental examinations including spirometry, capnography and pulse oximetry before, during and after physical activity. The analysis of survival was conducted on the basis of the dynamic follow-up of patients within 5 years (60 months).

Results. In the analysis of parameters of dyspnea at rest, all the parameters were higher in the group of patients with CHF (р<0.05). The distance walked by the patients with CHF in 6 minutes was 488.23±90.84 m, which was significantly less than in the control group (815.60±53.89 m, р=0.009). Dyspnea as the cause of stoppage/slowing down of walking in 6MWT, was also more often recorded in patients with CHF (93.8±3.0% and 48.0±5.1%, р=0.049). Besides, in 6MWT the patients noted: weakness in legs (50.1±5.0% in the group of CHF and 40.0±5.0% in the control group, р=0.014), palpitation (29.0±4.6% and 20.0±4.1%, respectively, р=0.004). Worsening of dyspnea parameters in 6MWT was more evident in patients with CHF than in the control group (р<0.01). In the CHF group, hypocapnic type of ventilation was revealed in 6MWT, analysis of РЕТСО₂ trend graphs revealed a wave-like increase in the parameters, the so called periodic breathing (PB). CO₂ trend was recorded in CHF group in 58.3±1.0% of cases (the difference with the control group with р=0.046), the trend of heart rate – in 18.8±0.3% of cases (р=0.027). Cox proportional hazards regression analysis of mortality in patients with CHF showed a prognostic significance of a complex model comprising the following parameters of a patient: body mass index (р=0.005), left ventricular end-diastolic dimension (р=0.034), left ventricular end-systolic dimension (р=0.002), left ventricular ejection fraction (р=0.041), 6MWT distance (р=0.004), desaturation (р=0.009), and the presence of signs of PB during 6MWT (р=0.005). Model coefficients were statistically significant at р<0.0001.

Conclusions. Dynamic capnography and pulse oximetry allow to identify signs of PB in patients with CHF during 6MWT which may deepen a complex assessment of parameters of the cardio-respiratory system in patients with CHF in order to determine tolerance to physical exercise as well as the effectiveness of the conducted treatment. Complex assessment of survival of patients with CHF showed prognostic significance of the following parameters of a patient: body mass index, left ventricular end-diastolic dimension, left ventricular end-systolic dimension, left ventricular ejection fraction, 6MWT distance, desaturation, PB during 6MWT.