The COVID-19 pandemic has emerged as the most significant public health crisis of the 21st century. As of the end of January 2023, global confirmed cases have exceeded 670 million, with a domestic cumulative total of 10.24 million cases, including occurrences of reinfection. Beyond acute symptoms following infection, patients and society face the challenge of long-term complications associated with COVID-19. Termed 'Post COVID-19 condition' or 'Long COVID' by the World Health Organization (WHO), this encompasses symptoms appearing within three months of the initial infection. Symptoms of Long COVID reveal chronic damage inflicted by the virus on multiple organ systems, including fatigue, cognitive impairment, chest tightness, palpitations, difficulty breathing, and depression.

Despite continuous efforts by healthcare professionals to find suitable treatments, no medication has been confirmed to effectively prevent or reduce post-COVID-19 sequelae. These health issues impose significant burdens and disturbances on patients' quality of life, economies, and societies.

According to the Ministry of Health and Welfare's report on the top 10 causes of death in the 111th year, aside from the marked increase in COVID-19 cases, there have been significant increases in hypertensive diseases, Cardiac diseases, and diabetes .Therefore, addressing the post-COVID-19 sequelae among chronic disease patients is an essential global health issue in the post-pandemic era.

Current research indicates that respiratory training is safe and effective in improving the exercise capacity, lung function, and alleviating respiratory difficulties in COVID-19 recovered patients. The impact of respiratory training on patients' respiratory and physical function remains uncertain, especially considering that many present-day infections are among non-hospitalized individuals with mild symptoms. Thus, exploring simple and effective respiratory training methods to reduce COVID-19's long-term impact on patients warrants continuous investigation.

Therefore, this study will employ Incentive spirometer-based respiratory training to assist COVID-19 patients who has diabetes, hypertensive disease, or cardiac disease in respiratory training. Data collection before and after the intervention will involve oxygen demand, blood parameters, the post-COVID-19 Functional Status scale (PCFS scale), and lung function indices, to investigate and evaluate the effectiveness of intervention respiratory training in improving Long COVID symptoms.

Inclusion Criteria:

1. Individuals who have contracted and recovered from COVID-19 within the past year must present proof of diagnosis, such as medical certificates or screening results. The ICD-10 diagnosis codes are: U07.1 for confirmed COVID-19 viral infection, and U09.0 for post-COVID-19 condition, unspecified. Recovery is defined as testing negative in a COVID-19 rapid test.
2. Never diagnosed with hypertensive diseases (ICD-10 codes: I10.x or I11.x), diabetes (ICD-10 codes: E10.x or E11.x), or heart diseases (ICD-10 codes: I25.x, I50.x, I65.x, or I67.x and classified as Class I or II by the New York Heart Association functional classification).
3. Exhibiting long-term respiratory symptoms related to COVID-19, such as post-exertional breathlessness, chest discomfort, cough, difficulty breathing, rapid breathing, etc., and meeting at least one of these criteria for inclusion.
4. Aged between 20 - 90 years.
5. Able to communicate in and understand Mandarin or Taiwanese, either verbally or non-verbally.
6. Willing to participate in the study and agree to be assigned.

Exclusion Criteria:

1. Patients with a functional status classified as level 5 or higher on the Modified Rankin Scale (MRS), indicating severe disability and bedridden status.

2. Patients suffering from dementia, such as Alzheimer's, Parkinson's disease, etc.

3. Patients with acute psychiatric symptoms who are unable to communicate.

4. Individuals with a high risk of litigation.

5. Patients suffering from Chronic Obstructive Pulmonary Disease (COPD) or any other respiratory system diseases.

6. Patients with moderate or severe heart disease, classified as Class III or IV by the New York Heart Association functional classification.

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