Nervous system disease imposes a great burden on society and individuals and causes various complications. The Neurological disease incidence rate in Korea is estimated to be 92.2 to 232 cases per 100,000 people based on data from the Korea Centers for Disease Control and Prevention and the National Health Insurance Corporation, and 46,496 to 105,000 new cases occur each year (Kim et al., 2019). Neurological disease is the fifth leading cause of death in Korea, and the mortality rate is decreasing, but the prevalence rate is increasing, so the burden continues to increase, and the related medical expenses also increased by more than 700 billion won from 2.3804 trillion won in 2015 to 3.1286 trillion won in 2019(Centers for disease control and prevention, 2022). Most of them remain as aftereffects, causing various neurological disorders, which interfere with daily life and require long-term treatment and nursing (Centers for disease control and prevention, 2024a). This causes economic problems due to the cost of devices and equipment for nursing or other facilities and the cost of nursing (Korean stroke society, 2024). Neurological disease can often cause secondary problems such as bedsores, aspiration pneumonia, joint contractures, fractures, central pain, urinary tract infections, and bowel disorders, and it is important to prevent these (Centers for disease control and prevention, 2024b).

Neurological disease causes a decrease in the patient’s ventilation and swallowing functions, which increases the incidence of pneumonia. Neurological disease damages the corticospinal tract, weakening the respiratory muscles on the opposite side of the damage and reducing chest wall movement (Lee, 2022). Paralysis and weakening of the diaphragm cause the diaphragm to rise more toward the head during rest, unlike normal, and the anterior inferior ribs are pulled inward, causing alveolar hypoventilation (Ellen H, 2017). In a pulmonary function test of 29 stroke patients, forced vital capacity, maximum expiratory pressure and inspiratory pressure, and forced expiratory volume in 1 second showed significant decreases compared to normal predicted values (Jung, 2014).

Among them, the peak cough flow rate reduction is an important indicator of pneumonia and complications. Reduced peak cough flow is caused by decreased inspiratory and expiratory muscle strength, laryngeal closure/opening, airways obstruction, restrictive lung disease, and age/activity (Brennan, 2022). In normal people, a strong cough reflex occurs when aspirated, but stroke patients have neurological damage that causes sensory disturbances in the larynx, which reduces the cough reflex and causes difficulty swallowing (Kulnik et al., 2016). The peak cough flow rate was significantly higher in patients with dysphagia than in the group without pulmonary complications (Bianchi et al., 2012). Therefore, the incidence of aspiration pneumonia in stroke patients was 16.8%, of which 60.7% occurred within 1 month, which was the most common (Seo et al., 1994), and 80% of stroke patients who could not cough developed respiratory infections (Belal et al., 2020). For every 100 liters per minute decrease in peak cough flow, the relative risk of 5-year mortality in the elderly was 1.16, which was a strong independent predictor (Cook et al., 1991). Therefore, prevention of complications, including pneumonia and respiratory failure, was a controllable factor affecting the survival rate and functional disability of stroke patients (Centers for disease control and prevention, 2022).

Patients with neurological disorders require respiratory physiotherapy to prevent survival and functional disability due to decreased peak cough flow. Chest expansion resistance exercise and respiratory muscle stretching applied three times a week for eight weeks in stroke patients increased peak expiratory flow (Lee, 2022). Cough ability was significantly improved in the experimental group that performed respiratory muscle training three times a week for eight weeks (Jo, 2015). When home-based expiratory muscle training was performed 6 times a week for 8 weeks for parkinson’s patients, the increase in voluntary peak cough flow was greater than in the control group (Reyes et al., 2018). This type of respiratory physiotherapy also helps with dyspnea. An exercise program consisting of cycling, strength training, and daily living training was performed once a week for 8 weeks for patients with idiopathic pulmonary fibrosis, and dyspnea was significantly reduced (Rammaert et al., 2011). In patients with pneumothorax who had a chest tube inserted, 30 minutes of deep breathing exercise significantly reduced dyspnea on the fourth day (Kim, 2000). However, it is difficult to do cough training due to the strengthening of infection control in the hospital and concerns about droplets as a route of infection transmission.

As a way to solve these problems, breathing exercises in a forest environment can be an alternative. When examining the effects of the forest environment on the respiratory system, 31 college students who participated in a 2-night, 3-day forest healing program in a national forest park showed improvements in cardiopulmonary health indices, and among them, peak expiratory flow increased (Li et al., 2022). Similarly, peak expiratory flow increased in 37 adults after a 1-day forest walk (Borriello et al., 2022). In Korea, when women over 60 years old were divided into 43 forest walkers and 19 city walkers and had a 30-minute walking activity, there was no significant change in the city walkers, but the forest walkers reported improvements in heart and lung function (Lee and Lee, 2014).

In a hospital setting, swallowing and coughing abilities are assessed and breathing exercises are applied to prevent respiratory complications in stroke patients, but it is difficult to implement due to the indoor environment and wearing a mask. As an alternative, breathing exercises in a forest environment may be helpful. Although general breathing exercises have been shown to improve pulmonary function and peak flow rate (Jo. 2015; Reyes et al., 2018; Lee 2022), studies specifically examining the effects of forest environment on breathing exercise in patients with neurological disorders are extremely limited (Nguyen et al., 2023). Therefore, this study was conducted to find out the changes in peak expiratory flow rate and dyspnea index of subjects when applying a forest environment to prevent complications in patients with neurological disorders, thereby helping to establish an appropriate treatment plan during treatment.

This study was conducted to investigate the effects of applying each environment on the changes in peak expiratory flow rate and dyspnea index of stroke patients after 15 minutes of single-time deep breathing exercise and coughing training in a forest environment (healing forest) and an indoor environment (in-hospital physical therapy room) with 15 stroke patients as subjects.

The purpose of this study is to investigate the effects of forest environment application on peak expiratory flow rate and dyspnea index of patients with neurological disorders. To this end, peak expiratory flow rate and dyspnea index were evaluated after 15 minutes of single deep breathing exercise and coughing training in forest environment and indoor environment. Peak flow meter was used to evaluate peak expiratory flow rate, and visual analog scale was implemented to evaluate dyspnea index. In this study, peak expiratory flow rate significantly differed depending on the environment, and Bonferroni post hoc analysis showed that it increased more in the forest environment than in the baseline and indoor environments. Dyspnea index also significantly differed depending on the environment, and Bonferroni post hoc analysis showed that it decreased more in the forest environment than in the indoor environment.

Li et al. (2022) reported that when healthy college students performed three activities of walking therapy, sitting therapy thereafter, and handmade work therapy for 2 nights and 3 days in a national forest park, the peak expiratory flow increased by 0.50 L/min for 2 hours. Borriello et al. (2022) also reported that the peak expiratory flow increased by 0.44L/min after a forest bathing program for normal people. This is consistent with the results of Lee and Lee (2014), who reported that there was no difference in forced expiratory flow in 1 second in the 30-minute urban walking group, but a significant difference in the forest walking group. The application of the forest environment to patients with neurological disorders was consistent with the results of normal people. In contrast, after breathing exercise indoors, there was an increase compared to the pre-value, but there was no significant difference. This was inconsistent with the study by Jo (2015) and Lee (2022). This is thought to be because the breathing exercise was applied three times a week for 8 weeks to patients with neurological disorders, but the present study conducted the experiment through breathing exercise for a single 15-minute period.

Rammaert et al. (2020) reported that dyspnea was reduced by 7mm after applying endurance training using a home bicycle, muscle strength training using resistance, and activity training of daily living for 30 to 45 minutes once a week for 8 weeks to patients with idiopathic pulmonary fibrosis. Kim (2000) reported that dyspnea was reduced by 18.4 mm after performing deep breathing training using vocalization for 30 minutes on patients with pneumothorax who had inserted a chest tube, and that, unlike the control group, it tended to continue to decrease until the 5^th day. These results are consistent with the result of a study that showed a 4.4 mm decrease in a forest environment compared to before performing breathing exercise, but did no match the result of 7.07 mm increase in an indoor environment. Antonelli et al. (2021) argued that forest environment exposure and respiratory function can be considered in terms of organic compound inhalation, autonomic nervous system response, and light physical activity. Lee and Lee (2012) reported that inhaling phytoncide, an organic compound emitted from forests, improved the subjects’ autonomic nervous system and reduced stress in 31 subjects. Song et al. (2019) reported that landscape appreciation was related to activating the parasympathetic nervous system and lowering the sympathetic nervous system and heart rate compared to urban landscape appreciation in 65 women, and that the total mood disorder score and state anxiety score were also lower. Lee et al. (2014) reported that after walking in the forest, sympathetic nervous system activity was suppressed and parasympathetic nervous system activity was significantly increased in heart rate variability compared to walking in the city, and in a questionnaire, negative mood was reduced and they felt more comfortable and natural. In contrast, hospitals, which are indoor environments, are thought to have reduced the benefits of respiratory function and felt more dyspnea due to reasons such as the recommendation to wear masks due to concerns about infection, anxiety about isolation due to infectious diseases (Moon and Lim, 2023), and patients with acute neurological at high risk of falls (Kim et al. 2013).

Therefore, when performing breathing exercises to improve coughing ability in patients with neurological disorders, it is suggested to perform them in an outdoor forest environment rather than an indoor hospital environment, as this may have a more immediate effect and may cause less dyspnea.

The limitations of this study are as follows: First, the number of subjects was small, making it difficult to interpret and generalize the results. The experiment was conducted on some patients with neurological disorders, so variables such as disease severity could not be controlled. Second, changes in weather conditions according to each environment could not be controlled, so there were differences in temperature and humidity in the forest environment. It is difficult to make an accurate comparison because variables according to weather conditions could not be controlled. Third, the experiment was conducted as a one-time breathing exercise, not as a long-term exercise program. Therefore, future research is need to investigate the effects of a long-term breathing exercise program on the respiratory function of patients with neurological disorders by considering weather conditions and targeting a larger number of subjects.

The purpose of this study was to investigate the effects of 15 minutes of one-time deep breathing exercise and coughing training on coughing ability and dyspnea index in forest and indoor environments for patients with neurological disorders. PFM was measured to evaluate peak expiratory flow after 15 minutes of one-time deep breathing exercise and coughing training in forest and indoor environments for 15 patients with neurological disorders, and VAS were performed to evaluate dyspnea index. The results of the study showed that 15 minutes of one-time deep breathing exercise and cough training in a forest environment increased peak expiratory flow and reduced dyspnea in patients with neurological disorders compared to 15 minutes of one-time deep breathing exercise and cough training in an indoor environment. Therefore, this study suggests that even one-time breathing exercise in a forest environment can have a positive effect on peak expiratory flow and dyspnea index in patients with neurological disorders, and can be helpful in establishing an appropriate treatment plan.