The results of the study demonstrated that self-care education has a positive effect on improving FVC and FEV1 of patients with COPD. In this regard, Decramer (
17) reported that the lung function tests of COPD patients obtained better results thanks to undergoing the rehabilitation program, which is in line with the findings of the present study. Collins et al. (
18) found a direct relationship between the rehabilitation program and the improvement of lung function tests. The authors observed that implementing the rehabilitation program had enhanced the function of respiratory muscles in 48% of patients. Similarly, in the present study, after the self-care program, an improvement was seen in the results of lung function tests in the intervention group; besides, lung function tests improved by 75% after administering the lung rehabilitation program on patients with COPD. Perry (
19) confirmed that lung function tests in COPD patients receiving lung rehabilitation showed better results, which is compatible with the present study. Investigating the impact of self-care training on respiratory and mood status of patients with COPD, Nasiri et al. (
20) reported that using this program exerts positive effects on breathing pattern, chest pain, and pulmonary sounds. In the study by Izadi et al. (
21), which examined the effect of breathing exercises on arterial oxygen saturation and respiratory pattern in patients with COPD, the results showed a rise in arterial oxygen saturation after the intervention, suggesting the favorable influence of these exercises on the respiratory status of patients. Izadi-Avangy et al. (
22) noted that while breathing training had a positive effect on arterial oxygen saturation and patients’ daily activities, it did not affect FEV1 and FVC. The reason for this inconsistency could be associated with differences in the duration of self-care follow-up as well as geographical variations between the research by Izadi-Avangy et al. and the present study. Moghaddasi et al. (
23), addressing the effect of exercise on clinical manifestations of pulmonary function in asthmatic patients, reported that exercise could reduce symptoms of asthma (such as wheezing, dyspnea, and coughing) and improve pulmonary function. Meamari et al. (
24) examined the impact of six weeks of structural corrective exercises along with respiratory muscle exercises on cardiopulmonary indices in ten-year-old children with kyphosis. Consistent with the present study, they reported that respiratory exercises had increased FVC and FEV1 values. Previous studies have proposed that pulmonary emphysema is a likely complication in patients with severe COPD. Thus, a large fraction of respiration is contained in the anatomical dead space and tachypnea occurs to compensate for respiration (
25). This reduces the activity of inspiratory muscles and eventually leads to weakness. In such cases, respiratory exercises, including lip-pursed breathing, raise the pressure of airways in the expiratory flow, thereby decreasing the accumulation of air flow and resistance in the airways, enhancing oxygen transfer, and enabling slow and deep breathing (
26). Moreover, respiratory exercise increases the use of ancillary muscles of the chest wall, amplifies the activity of abdominal muscles during inhalation, and simultaneously lowers the function of the diaphragm muscle. All of these changes help COPD patients experience more efficient breathing and require less oxygen (
27-
29). Concerning the possible effect of spirometry and pursed-lip breathing as part of the self-care training program in this study, it seems that the proposed breathing exercises have enhanced pulmonary ventilation in patients with COPD.
Several other studies have similarly confirmed that various types of breathing exercises can prolong exhalation, which in turn decreases respiratory rate, increases FVC, and ultimately boosts the efficiency of pulmonary ventilation (
27-
32). In short, given the chronicity of respiratory problems, which can limit one’s activities and exacerbate the symptoms, and the fact that no special equipment is needed to raise patients’ awareness, [self-care] training can be provided to people with COPD as a way to improve their respiratory status and thus help them adapt to disease conditions.