Scientists have extensively been discussing the necessity of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease (COPD), the main objectives of which are to reduce symptoms and improve the quality of life.1 It was found that the rehabilitation measures have a positive impact on important aspects of the patient's life. The results of several studies show that pulmonary rehabilitation could increase physical activity, oxygen consumption and patients' endurance, reduce the frequency and duration of hospitalization, and greatly improve the efficiency of therapy.2^-4 It follows that the improvement of treatment strategies in patients with COPD should provide rational conversion of standard schemes of therapy and rehabilitation in accordance with their clinical, pathogenic, functional and economic feasibility. Pulmonary rehabilitation is currently viewed as a key strategy in the management of respiratory system diseases.5 The selection process for the rehabilitation of patients take into account their functional status, severity of dyspnea, motivation level, and smoking status, although the creation of individualized programs for the integrated treatment of patients with COPD remains an unsolved problem of scientific and practical medicine. According to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) recommendations,6 the minimum length of an effective rehabilitation is 6-12 weeks (at least 12 sessions, 2 times per week, for at least 30 minutes). A complete rehabilitation program should include physical exercise, smoking cessation, nutritional therapy, patient education and psycho-emotional support.7 However, until now we have no effective program to maintain a therapeutic effect for a long time especially for the patient with comorbid pathology COPD and chronic heart failure (CHF). A perspective area of pulmonary rehabilitation is a full yogic breathing exercise.8 Therefore, the aim of the present study was to assess the effectiveness of pulmonary rehabilitation in addition to the standard medical care of patients with COPD and CHF.

The pre-specified duration of the enrollment period was two years and during that time we interviewed 168 patients. Forty-two did not meet inclusion criteria, 24 declined to participate. A total of 102 patients were enrolled, 54 to CG and 48 to IG.

At baseline, there were no significant (p > 0.05) differences between the groups in the patients' clinical characteristics (Table 1). At admission patients received in both groups standard therapy in comparable doses.

By the end of the observation period, a significant reduction in office heart rate (HR), respiratory rate (RR) at rest, severity of dyspnea by the Borg scale, the number of points by CES, and increased 6MWT distance were observed in both groups. Moreover, all these changes were more considerable in the IG as compared with the CG (Table 2).

Oxygen saturation increased in both groups (in CG: from 93 (84; 95)% to 94 (83; 97)%, p = 0.01; in IG: from 93 (84; 95)% to 98 (95; 98)%, p < 0.001), more pronounced in IG (p = 0.03).

A reduction of CHF FC (NYHA) was observed in 82% of the IG patients and only in 61% of the CG patients (χ² = 4.55, p = 0.03).

Average duration of hospitalization was shorter in the IG (16.7 ± 3.1 days versus 19.9 ± 3.8 days in CG, p < 0.05).

Thus, our findings showed that the application of pulmonary rehabilitation in addition to standard therapy in patients with CHF and COPD is associated with a significant increase of exercise tolerance and decrease in length of hospital stay.

One important extrapulmonary manifestation of COPD is skeletal and respiratory muscle dysfunction.10 With the increasing severity of the disease, COPD patients lose exercise endurance and often complain of fatigue and dyspnea. These symptoms curtail patients' ability to exercise and compromise cardiac fitness, which further limits their exercise tolerance, creating a vicious downward spiral that can eventually lead to generalized debility and immobility.11 Encouragingly, early interventions with exercise programs may restore some of the lost health status related to muscle dysfunction and increase patients' exercise tolerance and stamina.12^-14 On this basis, a perspective direction of physical rehabilitation among patients with COPD and CHF is training of respiratory muscles. By increasing the strength and endurance of the respiratory muscles, as well as improving the efficiency of gas exchange, application of the full yogic breathing leads to an improvement of spirometry indices and arterial oxygen saturation. In our research we obtained data of increased arterial oxygen saturation after practicing the full yogic breathing.

The positive impact of the yogic breathing exercises in the rehabilitation among patients with CHF and COPD has been described by many researchers. Thus, Soni et al.15 have noted a positive effect of yoga training on diffusion capacity in COPD patients. The results of another study16 have shown that 1 month of yoga practice, including breathing exercises, led to a significant reduction of dyspnea according to the visual analogue scales. A prospective, randomized, controlled study17 involving 24 patients with COPD, who performed pranayama in addition to standard therapy, has also shown the improvement of lung function parameters and quality of life. Similar results have been described by Bernardi et al.,18 who have noted an increase in exercise tolerance and a decrease in dyspnea severity after one month of performing the full yogic breathing by patients with CHF. In addition, Gomes-Neto et al.19 have shown that yoga practice, including breathing exercises, led to an increase in exercise tolerance in patients with CHF.

Mechanisms of influence of the full yogic breathing on the status of patients with CHF and COPD are not entirely clear. It is known that CHF is characterized by impaired autonomic regulation - decreased parasympathetic tone and, consequently, increased sympathetic activity.20 There is evidence of autonomic balance optimization and increasing sensitivity of arterial baroreflex on the background of yoga.21 By acting on lung tissue baroreceptors, as well as stretch receptors located in the smooth muscle layer of the large airways, slow deep yogic breathing activates the parasympathetic nervous system. The influence of yogic breathing on the respiratory and vasomotor centers of the medulla oblongata cannot be ruled out. This phenomenon may be based on some general respiratory and cardiac neuronal network.

In addition to active participation in the development of the respiratory muscles and autonomic balance optimization, deep yogic breathing reduces body weight, the effects on lipid peroxidation, normalizes blood pressure and HR, which is very important in the context of frequent comorbidity of respiratory and cardiovascular disease.

The study by Guleria et al. "Yoga is as effective as standard pulmonary rehabilitation in improving dyspnea, inflammatory markers, and quality of life in patients with COPD" has evoked a wide response, comparing the efficacy of yoga with standard pulmonary rehabilitation in patients with COPD.22 Scientists have found an equivalent reduction in C-reactive protein and interleukin-6 levels after performing pranayama as well as at the end of a standard pulmonary rehabilitation. These results allowed concluding that yoga is a cost-effective form of rehabilitation that is just as effective as standard rehabilitation.

Application of full yogic breathing in addition to standard therapy of patients with CHF and COPD is associated with a significant decrease in CHF FC and dyspnea severity, and an increase in exercise tolerance and arterial oxygen saturation.