Effectiveness of individualized nutritional support in improving clinical symptoms of patients with acute exacerbations of chronic obstructive pulmonary disease: a pre-post intervention study

Introduction

Chronic obstructive pulmonary disease (COPD) is a progressive and irreversible lung disease characterized by persistent airflow obstruction, primarily resulting from abnormalities in the airways (chronic bronchitis, bronchiolitis) and/or alveoli (emphysema) (1). It is one of the leading causes of mortality globally, responsible for over 3 million deaths annually, with nearly 90% of these occurring in individuals under the age of 70 in low- and middle-income countries (2). Additionally, COPD is also a major contributor to disability, as reflected in the global disability-adjusted life years (DALY) estimate of approximately 1,068 per 100,000 population, with the burden expected to increase due to aging populations and prolonged exposure to risk factors such as tobacco smoke and air pollution (3). COPD is a major public health challenge that is both preventable and treatable.

Malnutrition is a highly prevalent and clinically significant complication in patients with COPD, particularly during acute exacerbations. Previous studies suggested that 30–60% of COPD patients were malnourished, with even higher rates reported among hospitalized individuals (4,5). The high prevalence is attributed to a combination of physiological, metabolic, and behavioral mechanisms that impact both energy balance and nutrient intake (6).

The pathophysiology of these processes is multifactorial, consisting of systemic inflammation, elevated resting energy expenditure (REE), increased protein catabolism, and reduced muscle protein synthesis, which simultaneously lead to loss of fat-free mass (FFM) and muscle wasting (7). Moreover, hypermetabolism—particularly during acute exacerbations—results in an increased respiratory workload and higher energy demands (7,8). In parallel, factors such as dyspnea, anorexia, early satiety, altered taste sensation, and medication side effects reduce oral intake, exacerbating the energy-protein imbalance (6,8). Pulmonary cachexia, characterized by unintentional weight loss and muscle depletion, may occur independently of lung function severity and is a strong predictor of poor clinical outcomes (6,8). Notably, loss of skeletal muscle mass has been shown to predict mortality more robustly than the degree of airflow obstruction itself (7,8).

Interventions like oral nutritional supplements (ONS), dietary counseling, and multimodal approaches have been used to address malnutrition. A meta-analysis conducted by Peter et al. involving 13 randomized controlled trials (RCTs) in patients with COPD demonstrated that nutritional support measures—including dietary counseling, ONS, and enteral tube feeding—significantly improved daily energy and protein intake (9). A RCT by Arora et al. (10) demonstrated that supplementation with 600 kcal and 22 g of protein per day, in the form of ONS or between-meal snacks, over 12 months, improved body weight and quality of life in malnourished COPD patients.

In Vietnam, a randomized controlled intervention study by Nguyen et al. (11) utilized monthly dietary counseling over three months, based on a nutrition guide specifically tailored for COPD, for outpatient COPD patients. The results demonstrated significant improvements in energy intake, protein intake, and body weight after three months of intervention. Results showed that after three months of intervention, energy intake, protein intake, and body weight increased significantly. SGA score, inspiratory muscle strength, and quality of life scores improved considerably in the intervention group. However, in Vietnam, evidence on the role of individualized nutritional support among hospitalized COPD patients-particularly during acute exacerbations-remains scarce. Hospitalization represents a period of heightened metabolic stress and systemic inflammation, often accompanied by reduced oral intake and rapid muscle catabolism (7,8). These patients face an elevated risk of acute malnutrition and poor clinical outcomes (7,8), yet few studies have investigated how individualized nutritional care may influence short-term recovery during this critical phase. Furthermore, practical and ethical considerations in hospital settings-where nutritional care is a standard component of treatment-limit the feasibility of randomized controlled designs, creating a need for real-world observational and pre-post studies to assess clinical effectiveness and feasibility in routine practice.

Therefore, this study aimed to evaluate the short-term association between individualized nutritional intervention and improvements in nutritional status and clinical symptoms among hospitalized patients with acute exacerbations of COPD. The findings are expected to provide preliminary, context-specific evidence to inform future large-scale, controlled studies and the integration of tailored nutritional support into comprehensive inpatient COPD management. We present this article in accordance with the TREND reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1261/rc).

Methods

Study design and setting

This was a pre–post intervention study without a control group conducted at the Department of Chronic Pulmonary Diseases, National Lung Hospital (Hanoi, Vietnam), from January to December 2023.

A pre–post design was selected because withholding nutritional intervention from malnourished COPD patients was considered ethically inappropriate, and all eligible participants required nutritional care as part of standard treatment. This design also enabled the evaluation of short-term changes in nutritional and clinical parameters following individualized nutritional intervention under real-world hospital conditions.

Participants were assessed at three time points: T0 (within 24–48 hours after admission), T7 (after 7 days of intervention), and T40 (after 40 days). The 40-day follow-up was selected to capture both in-hospital and early post-discharge effects, reflecting short-term nutritional and clinical outcomes. This period allowed observation of changes in body weight, serum albumin, and key symptoms while ensuring feasibility and adherence to the individualized nutrition intervention.

Participants

The participants in this study were required to meet the following inclusion criteria: (I) aged 18 years or older; (II) diagnosed with an acute exacerbation of COPD according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria; (III) having a complete medical record at the National Lung Hospital; (IV) expected to be hospitalized for at least 7 days; (V) must be managed or willing to be managed by the Chronic Pulmonary Disease Management Unit (CMU); (VI) permission from the treating physician to participate in the nutritional intervention model; (VII) voluntarily agree to participate in the study and sign a written informed consent. Exclusion criteria included: (I) pregnant women; (II) patients in critical condition requiring emergency care or intensive treatment; (III) patients requiring intravenous nutrition or contraindicated for enteral nutrition; (IV) individuals with severe body deformities or generalized edema; (V) individuals experiencing acute exacerbations of other conditions such as renal or liver failure; (VI) patients with cognitive disorders or those unable to understand and comply with the study requirements, as well as those who refuse to participate, will be excluded.

Sample size and sampling

In this study, participants were selected through a two-stage sampling process. In the first stage, a convenience sampling technique was used to recruit participants with COPD. In the second stage, patients who met the eligibility criteria were selected to participate in the nutritional intervention. The study was designed as a pilot pre–post feasibility investigation conducted in a real-world inpatient setting; thus, all eligible patients admitted during the recruitment period were included.

During this period, the vast majority of hospitalized COPD patients were male, consistent with national and regional epidemiological data showing that over 80–90% of COPD hospital admissions in Vietnam are male, primarily due to the markedly higher smoking prevalence among men. Notably, Ngo et al. [2019] reported that 93.0% of inpatients with COPD at the Respiratory Center of Bach Mai Hospital were male (12), while Nguyen et al. [2019] at the National Lung Hospital found that 89.9% of outpatients with COPD were male (13). We fully acknowledge that this sex imbalance restricts the extrapolation of our findings to female patients. Future larger-scale studies should recruit a gender-balanced cohort to verify whether sex-related physiological differences may influence nutritional responses.

We used sample size calculations for estimating a mean difference in a pre-post intervention design within the same group of subjects. The criterion for evaluating the effectiveness of the intervention was the improvement in serum albumin levels following the intervention. Data from a previous study were used, indicating that the mean serum albumin level increased by 1 g/L after the intervention, with a standard deviation of 2 g/L (14).

n=2C(1−r)(ES)2[1]

For the sample size calculation, we applied the formula using the coefficient C=(Zα/2+Zβ)2, where α=0.05 and β=0.2. According to the standard C-value table, this yielded C =7.85. The effect size (ES) was estimated using the formula ES=d¯s, where d¯ represents the expected mean difference (1 g/L) and s is the standard deviation (2 g/L), resulting in an ES of 0.5. The correlation coefficient (r) between pre-and post-intervention measurements was assumed to be 0.6. Based on these parameters, the minimum required sample size was 25 patients, which was increased to 30 to account for a 20% potential dropout.

The small sample size (n=30) and male-only composition indeed limit the generalizability of our findings. However, given the pilot nature and real-world hospital context of this study, the parameters used (α=0.05; β=0.2; expected mean change =1 g/L; SD =2 g/L; r=0.6) were appropriate for the study objectives. The nutritional intervention diagram is presented in Figure 1. No stratification by exacerbation severity was performed due to the limited sample size.

Figure 1 The nutritional intervention diagram. Flowchart illustrating the enrollment process, intervention procedures, and follow-up assessments. A total of 140 participants were screened, and 30 individuals who met the intervention criteria were included. Nutritional status assessments were performed at T0, T7, and T40. The assessments consisted of anthropometric indices, SGA, dietary intake evaluation, and laboratory tests (conducted at T0 and T40). Nutrition counseling, dietary provision, monitoring, and sample menu support were provided throughout the intervention period. T0: baseline (day 0); T7: day 7; T40: day 40.

Participants in the intervention group received an individualized nutritional care plan, initiated within the first 48 hours of hospital admission and maintained for approximately 40 days, including both inpatient and post-discharge phases. The intervention protocol was designed based on current clinical guidelines and tailored to the specific needs and clinical status of each patient.

Baseline nutritional assessment (T0)

Within 24–48 hours of admission, patients underwent a comprehensive nutritional assessment comprising anthropometric measurements (weight, height, body mass index (BMI), mid-upper arm circumference (MUAC), and calf circumference), 24-hour dietary recall, and the Subjective Global Assessment (SGA). Laboratory parameters, including serum albumin, were obtained to support the diagnosis. Based on the collected data, nutritional status was classified, and malnutrition was diagnosed when applicable.

Individualized nutritional prescription

Energy and nutrient requirements were calculated using standard predictive equations adjusted for disease-related metabolic stress and inflammation. Nutritional goals were set as follows (15):

• Energy: 30–35 kcal/kg body weight/day.
• Protein: 1.2–1.7 g/kg body weight/day.
• Lipids: 30–45% of total energy.
• Carbohydrates: 40–55% of total energy.

Nutrition was primarily delivered via the enteral route (oral or feeding tube). High-energy meal options included energy-dense soups and porridges, ONS, and specific nutrient-enriched additives such as protein powders or lipid emulsions.

Individualized counseling was provided by trained nutritionists, incorporating eating schedules, food choices, strategies to manage symptoms, and guidance on supplemental feeding. Educational materials were distributed to enhance adherence.

Implementation and monitoring

All dietary prescriptions were recorded in the hospital information system (ISOFH). Daily meals were prepared by the hospital kitchen according to standard operating procedures. Nutritional technicians supervised food hygiene, portion accuracy, and sample retention. Nutritional products and intravenous solutions were dispensed and administered under medical orders.

Daily monitoring included:

• Actual dietary intake via direct observation and 24-hour recall;
• Gastrointestinal symptoms and tolerance;
• Fluid balance monitoring if indicated;
• Adjustment of meal plans if intake consistently fell below 75% of estimated needs.

Data collection was performed by trained research staff using standardized instruments.

Follow-up evaluations (T7 and T40)

On day 7 (T7), nutritional reassessment was performed, including anthropometry, SGA, and dietary intake analysis. The nutrition plan was modified if needed based on clinical progress.

At day 40 (T40), patients returned for follow-up. Comprehensive re-evaluation included all baseline parameters, and dietary intake was reassessed using 24-hour recall and dietary records maintained post-discharge. Adherence was evaluated via the review of food diaries.

Discharge counseling and post-hospital follow-up

Before discharge, each patient received personalized dietary counseling, including:

• Estimated energy and protein needs;
• Instructions for preparing high-energy meals using common foods;
• A sample high-energy meal plan (Table S1);
• A 24-hour food diary template (Table S2).

Post-discharge, patients were contacted weekly via telephone for four weeks to reinforce compliance and provide dietary support as needed. Food diaries were collected at follow-up visits for analysis of intake patterns.

Data collection

Data were collected at three time points: within 24–48 hours of hospital admission (baseline), at day 7, and at day 40 post-intervention. Trained nutritionists conducted standardized interviews and clinical assessments, and all measurements followed validated protocols to ensure data quality and consistency.

General characteristics

Sociodemographic and clinical information included age, sex, ethnicity, education level, occupation, smoking status, and COPD-related symptoms. These were obtained via structured face-to-face interviews during the initial hospital stay.

Assessment of nutrition

We evaluated the anthropometry of participants, including height and weight, MUAC, and handgrip strength (HGS).

Anthropometry: we measured standing height using a standard height ruler with an accuracy of 0.1 cm. For weight measurement, we used an electronic scale with an accuracy of 0.1 kg, and calibration was done before measurement. Both height and weight measurements were done twice, and the average value was recorded. BMI is calculated by taking a person’s weight, in kilograms, divided by their height, in meters squared. Based on BMI, cutoff points for the classification of nutritional status in adults were: underweight with BMI <18.5 kg/m², normal weight with BMI between 18.5–24.9 kg/m², overweight with BMI between 25–29.9 kg/m², and obesity greater than or equal to 30 kg/m² (16). In addition, Chronic Energy Deficiency (CED) was defined as BMI <18.5 kg/m² and categorized into three levels of severity: mild (17.0–18.4 kg/m²), moderate (16.0–16.9 kg/m²), and severe (<16.0 kg/m²), to further stratify undernutrition status (17).

MUAC: we used a MUAC tape, a soft and non-stretch tape with an accuracy of 0.1 cm, to measure MUAC. The mid-point between the tip of the shoulder and the tip of the elbow in the left upper arm was determined and marked. Stretching the patient’s arm, looping the tape around the marked point with moderate tension, and reading the result to the nearest 0.1 cm.

HGS: HGS was measured using a Smedley dynamometer. Participants were instructed to hold the dynamometer with the arm at their side, elbow flexed at 90 degrees, and to squeeze as hard as possible for 3 seconds while exhaling. Each hand was tested twice alternately, and the highest value was recorded, accurate to 0.1 kg.

Serum albumin: blood samples were collected for serum albumin analysis. Serum albumin levels below 35 g/L were considered indicative of hypoalbuminemia (18).

Dietary intake: the 24-hour dietary intake was recorded through interviews with the patient and/or their caregiver, supplemented with medical record data (parenteral nutrition and therapeutic diet codes). Patients were guided to recall all food and drink consumed in the previous 24 hours, starting from the morning of the previous day to the morning of the current day. Visual aids, including the “Common Vietnamese Food Album” and food photographs from the National Institute of Nutrition, were used to help estimate portion sizes accurately.

SGA: nutritional status was assessed using the SGA, a validated clinical tool that integrates medical history (weight change, dietary intake, gastrointestinal symptoms, functional capacity) and physical examination (muscle wasting, subcutaneous fat loss, edema). Based on overall clinical judgment, patients were classified into three categories: SGA-A = well-nourished; SGA-B = moderately malnourished; SGA-C = severely malnourished (19).

Clinical symptoms

Patients were interviewed to assess nutrition-related clinical symptoms, including fatigue, dyspnea, anorexia, dysphagia, and abdominal bloating. Participants were asked to provide detailed descriptions regarding the onset, duration, and severity of each symptom. These data were used to support the assessment of nutritional risk and classification according to the SGA tool.

Statistical analysis

Data were entered using EpiData 3.1 and analyzed with Stata 14.0. Continuous variables are presented as means, and categorical variables as percentages. Normality of continuous data was assessed using the Kolmogorov-Smirnov test.

For comparisons between two independent groups, independent t-tests or Mann-Whitney U tests were applied, depending on data distribution. For pre-post comparisons within the same group, paired t-tests or Wilcoxon signed-rank tests were used. Changes in proportions were assessed using the McNemar test.

A P value of <0.05 was considered statistically significant.

Ethical statement

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of the National Lung Hospital (Decision: 776/QĐ-BVPTƯ). Informed consent was taken from all the patients. They had the right to withdraw at any time without explanation. All collected data were used solely for research purposes and kept strictly confidential.

Results

Table S3 shows the characteristics of 170 patients with COPD at the first stage of the sampling process. In which, 41.4% of patients were under 65, with a mean age of 67.2±8.5 years (range, 44–85 years). Most patients (92.1%) were retired, and 72.1% had completed lower secondary education. The proportion of former smokers was 87.1%. Among the 30 patients selected for nutritional intervention, 66.7% were over 65, with a mean age of 68.4±8.6 years. Of these, 96.7% were former smokers, with an average smoking duration of 33.6±12.6 years (range, 10–50 years), and 86.7% were retired.

Table 1 presents anthropometric characteristics of patients receiving interventions by age group. The overall mean weight was 49.8±8.8 kg; in patients over 65, it was 48.7±8.6 kg, with no significant difference compared to those under 65 (P=0.07). The overall CED prevalence was 46.4%, including 17.9% mild, 11.4% moderate, and 17.1% severe cases. CED prevalence was 43.1% in the under-65 group and 48.8% in the over-65 group, with no significant difference (P=0.65). HGS in the over-65 group was 21.2±9.0 kg, significantly lower than the under-65 group (P=0.001). MUAC was 23.6±2.9 cm, with no significant difference between groups (P=0.06). According to the SGA classification, 75.7% of patients had mild to moderate malnutrition (SGA-B), 12.9% had no risk (SGA-A), and 11.4% had severe malnutrition (SGA-C). Serum protein levels <60 g/L were found in 7.1% of patients, and serum albumin <35 g/L in 20%.

Figure 2 shows the clinical symptoms of COPD patients before and after intervention. Initially, fatigue (93.3%), dyspnea (90%), anorexia (60%), dysphagia (10%), and abdominal bloating (16.7%) were reported. After 40 days, these decreased to 53.3%, 33.3%, 26.7%, 3.3%, and 3.3%, respectively (P=0.73).

Figure 2 Symptoms of COPD patients before and after intervention. The radar chart shows the prevalence (%) of common symptoms in COPD patients, including fatigue, dyspnea (shortness of breath), anorexia (loss of appetite), dysphagia (difficulty swallowing), and abdominal bloating, measured before intervention (blue dotted line) and after 40 days of intervention (orange dotted line). COPD, chronic obstructive pulmonary disease.

Figure 3 illustrates the nutritional status of COPD patients by SGA at three time points: before, 7 days, and 40 days after intervention. Initially, 60% were SGA-B and 23.3% SGA-C. After 40 days, SGA-B decreased to 20%, SGA-C to 0%, while SGA-A increased from 16.7% to 80%.

Figure 3 Nutritional status of COPD patients before and after intervention according to SGA. The stacked bar chart presents the distribution of nutritional status based on the SGA in COPD patients at three time points: before intervention, after 7 days, and after 40 days of intervention. SGA categories include: SGA-A (well-nourished), SGA-B (moderately malnourished), and SGA-C (severely malnourished). Percentages within each bar indicate the proportion of patients in each SGA category. COPD, chronic obstructive pulmonary disease; SGA, Subjective Global Assessment.

Table 2 presents changes in anthropometric indicators and serum albumin levels at three time points: before intervention (T0), after 7 days (T7), and after 40 days (T40). At T0, 30 patients began the intervention, with a mean age of 68.4±8.6 years; 66.7% were over 65, and 96.7% had a smoking history averaging 33.6±12.6 years. Most (86.7%) were retired. Average weight increased from 46.9±6.4 (T0) to 47.8±6.2 kg (T40). BMI rose from 17.7±2.2 (T0) to 18.1±2.3 kg/m² (T40). The CED rate dropped from 70% to 53.3% (P=0.06). Serum albumin improved significantly from 36.4±0.7 to 38.3±0.7 g/L (P=0.005).

Discussion

To our knowledge, this is one of the first clinical nutrition intervention studies conducted in Vietnam to evaluate the impact of individualized nutrition support on hospitalized patients with acute exacerbations of COPD. Over a 40-day intervention period, participants showed significant improvements in body weight, serum albumin levels, and nutritional classification by SGA. Additionally, clinical symptoms such as fatigue, dyspnea, and anorexia were markedly reduced. These findings support the role of tailored nutrition therapy as a cornerstone in the comprehensive management of COPD-related malnutrition.

The present study revealed a high prevalence of malnutrition among COPD patients at baseline, with 70% classified as having CED by BMI criteria and 83.3% as moderately to severely malnourished based on SGA. Following 40 days of nutritional intervention, these rates declined markedly to 53.3% (CED) and 20% (SGA-B), respectively. This substantial reduction confirms the beneficial role of nutritional support and aligns with prior research demonstrating the effectiveness of personalized nutritional interventions in improving the nutritional status of COPD patients (11,20,21). Notably, the sharp decrease in patients classified as SGA-C and the marked increase in well-nourished patients (SGA-A) reflect not only metabolic recovery but also enhanced clinical perception of nutritional improvements. These findings are consistent with previous evidence that SGA may detect early malnutrition more sensitively than BMI, as it integrates weight change, dietary intake, functional capacity, and muscle wasting (22-24).

The nutritional intervention was associated with marked reductions in common COPD symptoms, including fatigue, dyspnea, anorexia, dysphagia, and bloating. Fatigue and dyspnea, the most debilitating symptoms affecting quality of life, were significantly alleviated. These improvements are in agreement with findings from previous studies showing that targeted nutritional support can lead to meaningful symptomatic relief in COPD patients (25,26). Potential mechanisms for these improvements include enhanced energy metabolism, reduction in systemic inflammation, and improved respiratory muscle strength driven by adequate protein and micronutrient intake (6-8). Moreover, restoring nutritional status may interrupt the vicious cycle of malnutrition, exacerbating symptoms, a well-recognized pathophysiological loop in COPD. This could explain the relatively rapid symptom resolution observed, especially in terms of fatigue and dyspnea, which may reflect early gains in functional capacity and overall energy balance (6,8).

Anthropometric parameters, including body weight, BMI, MUAC, and HGS, all improved significantly after the intervention. While the absolute changes were modest, their statistical significance is consistent with other clinical nutrition studies (10,11,27). For example, Nguyen et al. reported comparable increases in weight and MUAC after three months of dietary intervention in COPD patients (11). Improvement in HGS—a reliable marker of muscle function and physical performance—suggests that nutritional therapy contributed positively to patients’ functional recovery (8,26). These findings reinforce the role of nutrition in preserving muscle mass and enhancing physical capacity, both of which are crucial in the clinical management of COPD.

Additionally, serum albumin levels, which are often reduced in COPD due to chronic inflammation and inadequate protein intake, showed a significant increase from 36.4 to 38.3 g/L. This improvement supports the hypothesis that nutritional interventions can mitigate inflammation and restore protein reserves. It is in line with findings from both domestic and international studies reporting positive albumin responses following nutritional support (19-21,28). Although albumin can be influenced by non-nutritional factors, the consistent elevation post-intervention likely reflects both reduced inflammatory burden and improved dietary protein adequacy. As a key biomarker of nutritional status, serum albumin remains a useful parameter for monitoring nutritional recovery in COPD patients.

This study possesses several strengths, including a clearly defined nutritional protocol, individualized patient care, and consistent follow-up within a real-world hospital setting. Nevertheless, several limitations should be acknowledged.

First, the pre–post design without a control group limits the ability to attribute observed improvements solely to the nutritional intervention, as effects from standard medical treatment or natural recovery cannot be excluded. Second, the small sample size (n=30) comprising only male participants reduces statistical power and limits generalizability to broader patient populations, particularly females. Third, the 40-day intervention period was relatively short, preventing assessment of long-term outcomes such as sustained weight gain, reduced hospital readmissions, or mortality. Fourth, malnutrition severity was not stratified according to COPD exacerbation grade, which could have provided valuable insights into differential treatment responses. Fifth, serum prealbumin—a more sensitive biomarker of short-term nutritional change—was not measured due to laboratory constraints. Finally, the absence of multivariate analyses precluded adjustment for potential confounders such as disease severity, inflammation, or pharmacologic therapy.

Despite these limitations, this exploratory clinical study demonstrated that individualized nutritional support was associated with significant improvements in nutritional status, biochemical parameters, and clinical symptoms among inpatients with acute exacerbations of COPD. The findings emphasize the importance of early nutritional screening and targeted intervention during acute exacerbations. Future studies should include larger, gender-balanced samples, longer follow-up periods, and randomized controlled designs to establish causality and evaluate long-term outcomes. Integrating structured, individualized nutritional care into standard COPD management protocols could further optimize clinical outcomes and enhance patients’ quality of life.

Conclusions

Individualized nutritional intervention was associated with notable improvements in nutritional status, biochemical markers, and clinical symptoms among patients hospitalized with COPD. These findings underscore the potential importance of incorporating tailored nutritional care into comprehensive COPD management strategies to enhance recovery and quality of life. Nevertheless, due to the limited sample size, single-center design, and short follow-up duration, these results should be interpreted with caution. Future RCTs with larger, gender-balanced cohorts and extended follow-up periods are needed to confirm the long-term benefits and elucidate the causal relationship between nutritional intervention and clinical outcomes in COPD.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the TREND reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1261/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1261/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1261/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1261/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of the National Lung Hospital (Decision: 776/QĐ-BVPTƯ). Informed consent was taken from all the patients. They had the right to withdraw at any time without explanation. All collected data were used solely for research purposes and kept strictly confidential.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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