Preserved Ratio Impaired Spirometry (PRISm) is characterized by a normal forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) ratio but an FEV1 below 80% of the predicted value. It has a population prevalence of approximately 10% and is associated with marked symptoms, a high risk of acute exacerbations, and increased mortality. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) defines PRISm as a pre-chronic obstructive pulmonary disease (COPD) state, and 20%-30% of patients with PRISm will progress to COPD. Currently, no evidence-based therapy exists for PRISm; management is mainly symptomatic relief, and there is an urgent need for evidence-based support. This single-arm clinical trial preliminarily evaluates the efficacy and safety of budesonide/glycopyrronium/formoterol inhalation aerosol in symptomatic patients with PRISm. Symptomatic smokers who meet the diagnostic criteria for PRISm and have an FEV1/FVC ratio ≥0.7 and <0.8 are enrolled and treated with budesonide/glycopyrronium/formoterol inhalation therapy for 12 weeks. The primary endpoint is the change from baseline in FEV1; secondary endpoints include symptom score (COPD Assessment Test, CAT) and quality of life (St George's Respiratory Questionnaire, SGRQ); safety is assessed by recording adverse events (e.g., cardiovascular events); and exploratory analyses examine the association between biomarkers (e.g., peripheral blood eosinophil count, serum IgE level) and treatment efficacy. The study aims to preliminarily explore the efficacy and safety of budesonide/glycopyrronium/formoterol inhaler therapy for PRISm. Early intervention may delay the progression from PRISm to COPD, reduce the burden of chronic respiratory disease, and have important clinical translational value and public health significance.

Inclusion Criteria:

1. Age 40-75 years;
2. Smoking history ≥10 pack-years;
3. Pulmonary function test showing 0.7 ≤ FEV1/FVC < 0.8 and FEV1 < 80% predicted;
4. Presence of at least one chronic respiratory symptom (e.g., cough, sputum, dyspnea) lasting ≥3 months;
5. Voluntarily sign a written informed consent form, be able to understand the study objectives, and comply with follow-up requirements;
6. The investigator assesses that the subject is able to complete the 12-week treatment and follow-up and has good medication adherence.

Exclusion Criteria:

1. Concomitant Respiratory Diseases: (1) Diagnosed asthma, bronchiectasis, interstitial lung disease, active tuberculosis, or lung cancer. (2) Meeting the diagnostic criteria for chronic obstructive pulmonary disease (COPD) (post-bronchodilator FEV1/FVC < 0.7). (3) Acute respiratory infection or exacerbation within 4 weeks prior to enrollment.
2. Cardiovascular Disease Risks: (1) Uncontrolled hypertension (systolic blood pressure ≥180 mmHg or diastolic blood pressure ≥110 mmHg). (2) Myocardial infarction, unstable angina, malignant arrhythmia, or cardiac insufficiency (NYHA class ≥III) within the past 6 months. (3) Long-term use of beta-blockers or antiarrhythmic drugs.
3. Drug-Related Contraindications: (1) Allergy to budesonide, glycopyrronium bromide, formoterol, or excipients of the inhalation aerosol. (2) Use of long-acting bronchodilators (LABA, LAMA), inhaled corticosteroids, or immunosuppressants within 4 weeks prior to enrollment.
4. Other Systemic Diseases: (1) Severe hepatic or renal insufficiency (ALT/AST > 3 times the upper limit of normal, or eGFR < 30 mL/min/1.73m²). (2) Uncontrolled diabetes (HbA1c > 9%) or hyperthyroidism.
5. Special Populations and Compliance Issues: (1) Pregnant or lactating women, or women planning pregnancy without using effective contraception. (2) History of substance abuse, psychiatric disorders, or cognitive impairment that may affect study compliance. (3) The investigator deems the subject unsuitable for participation for other reasons (e.g., life expectancy < 1 year, inability to complete follow-up).