Obstructive airway diseases, particularly bronchial asthma and chronic obstructive pulmonary disease (COPD), are major contributors to respiratory morbidity worldwide. Both conditions are characterized by airflow limitation that can significantly impair quality of life and functional capacity. Although asthma is typically associated with variable and reversible airway obstruction, COPD is characterized by persistent airflow limitation with varying degrees of reversibility. Accurate assessment of airway function is therefore essential for diagnosis, therapeutic monitoring, and evaluation of disease progression [1,2].

Spirometry remains the cornerstone for the assessment of pulmonary function in patients with obstructive airway diseases. Parameters such as forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and the FEV₁/FVC ratio provide objective measures of airway obstruction and are widely used in both clinical practice and research. Current recommendations continue to emphasize spirometry as the standard method for evaluating airflow limitation and monitoring treatment response in patients with asthma and COPD [2,3].

Bronchodilator therapy forms a fundamental component of the management of obstructive airway diseases. By relaxing airway smooth muscle and reducing airflow resistance, bronchodilators improve lung function, alleviate symptoms, and enhance exercise tolerance. Assessment of bronchodilator responsiveness through spirometry offers valuable information regarding airway reversibility and treatment effectiveness [3,4].

Recent studies have demonstrated that bronchodilator responsiveness is a heterogeneous phenomenon and may vary according to disease phenotype, severity, and underlying pathophysiological mechanisms. Significant bronchodilator responses are more frequently observed in patients with asthma; however, a substantial proportion of patients with COPD may also exhibit measurable improvements in spirometric indices following bronchodilator administration [4,5].

The evaluation of pulmonary function before and after bronchodilator therapy not only assists in assessing therapeutic efficacy but also contributes to better characterization of obstructive airway diseases. Furthermore, the magnitude of bronchodilator responsiveness may provide insights into disease behavior and long-term clinical outcomes [5,6].

In view of the clinical importance of spirometric assessment and bronchodilator responsiveness, the present study was undertaken to assess pulmonary function in patients receiving bronchodilator therapy and to evaluate changes in spirometric parameters following bronchodilator administration.

Study Design and Setting: A prospective observational study was conducted at a tertiary care teaching hospital. The study was undertaken after obtaining necessary approvals. Written informed consent was obtained from all participants prior to enrollment. Study Population: Patients diagnosed with obstructive airway disease and receiving bronchodilator therapy were recruited from the outpatient and inpatient services of the hospital. Sample Size: Based on previous studies evaluating changes in pulmonary function parameters following bronchodilator administration, a minimum sample size of 120 participants was estimated to provide adequate statistical power for detecting clinically meaningful differences in spirometric indices. To compensate for possible incomplete data and participant attrition, a total of 135 patients were included in the study. Inclusion Criteria: 1. Patients aged 18–65 years. 2. Patients with a confirmed diagnosis of bronchial asthma or chronic obstructive pulmonary disease (COPD). 3. Patients receiving inhaled bronchodilator therapy for at least four weeks before enrollment. 4. Patients willing to provide written informed consent. Exclusion Criteria: 1. Patients experiencing acute exacerbation of respiratory illness at the time of evaluation. 2. Individuals with restrictive lung diseases, pulmonary fibrosis, active pulmonary tuberculosis, or lung malignancy. 3. Patients with significant cardiovascular disorders that could interfere with spirometric testing. 4. Pregnant women. 5. Patients unable to perform acceptable spirometric maneuvers according to standard guidelines. Study Procedure: Demographic details including age, sex, body mass index (BMI), smoking status, duration of illness, and duration of bronchodilator therapy were recorded using a structured data collection form. Pulmonary function testing was performed using a computerized spirometer calibrated daily according to manufacturer recommendations. Participants were instructed regarding the testing procedure and were allowed adequate practice before formal recording. Spirometry was conducted with the subject in a sitting position while wearing a nose clip. The following pulmonary function parameters were measured: • Forced Vital Capacity (FVC) • Forced Expiratory Volume in the First Second (FEV₁) • FEV₁/FVC Ratio • Peak Expiratory Flow Rate (PEFR) • Forced Expiratory Flow between 25% and 75% of FVC (FEF₂₅–₇₅%) Three technically acceptable maneuvers were obtained for each participant, and the highest value meeting acceptability criteria was used for analysis. For assessment of bronchodilator response, baseline spirometry was performed before administration of a short-acting bronchodilator. Subsequently, 400 µg of inhaled salbutamol was administered through a metered-dose inhaler with a spacer. Repeat spirometry was conducted 15–20 minutes after bronchodilator administration. The difference between pre-bronchodilator and post-bronchodilator values was recorded and analyzed. Outcome Measures: The primary outcome measure was the change in FEV₁ following bronchodilator administration. Secondary outcome measures included changes in FVC, FEV₁/FVC ratio, PEFR, and FEF₂₅–₇₅%. Statistical Analysis: Data were entered into Microsoft Excel and analyzed using Statistical Package for the Social Sciences (SPSS) version 26.0. Continuous variables were expressed as mean ± standard deviation, while categorical variables were presented as frequencies and percentages. The normality of data distribution was assessed using the Shapiro–Wilk test. Pre- and post-bronchodilator pulmonary function parameters were compared using the paired t-test for normally distributed variables and the Wilcoxon signed-rank test for non-normally distributed variables. A p-value <0.05 was considered statistically significant.

The mean age of the study participants was 46.8 ± 12.4 years. The largest proportion of patients belonged to the 46–60 years age group (36.3%), followed by the 31–45 years age group (28.1%). Males constituted 60.7% of the study population, while females accounted for 39.3%. The mean body mass index was 24.7 ± 3.8 kg/m². Among the participants, 37.8% were smokers and 62.2% were non-smokers. The mean duration of respiratory illness was 6.2 ± 3.5 years. Bronchial asthma was present in 57.8% of patients, whereas 42.2% had chronic obstructive pulmonary disease (Table 1).

A significant improvement was observed in all evaluated spirometric parameters following bronchodilator administration. The mean FEV₁ increased from 1.78 ± 0.54 L to 2.08 ± 0.57 L, demonstrating a mean improvement of 0.30 ± 0.15 L (p < 0.001). Similarly, mean FVC increased from 2.72 ± 0.68 L to 2.95 ± 0.70 L, with a mean difference of 0.23 ± 0.14 L (p < 0.001).

The mean FEV₁/FVC ratio increased from 65.4 ± 8.6% to 70.5 ± 8.1%, while PEFR improved from 258.6 ± 72.4 L/min to 301.8 ± 74.1 L/min. The mean FEF₂₅–₇₅% also showed a significant increase from 1.42 ± 0.58 L/s to 1.76 ± 0.62 L/s. All observed changes were statistically significant (p < 0.001), indicating a favorable response to bronchodilator therapy (Table 2).

Based on standard bronchodilator responsiveness criteria, 89 patients (65.9%) demonstrated a significant bronchodilator response, whereas 46 patients (34.1%) did not meet the criteria for significant reversibility. Thus, approximately two-thirds of the study population exhibited clinically meaningful improvement in pulmonary function following bronchodilator administration (Table 3).

Bronchodilator responsiveness differed significantly between patients with bronchial asthma and those with COPD. Among patients with bronchial asthma, 61 (78.2%) demonstrated a significant bronchodilator response, whereas only 17 (21.8%) showed a non-significant response. In contrast, among patients with COPD, 28 (49.1%) exhibited significant responsiveness while 29 (50.9%) did not. The difference between the two diagnostic groups was statistically significant (χ² test, p < 0.001), indicating greater reversibility of airway obstruction among patients with asthma (Table 4).

Correlation analysis revealed a statistically significant negative association between disease duration and improvement in FEV₁ following bronchodilator administration (r = −0.312, p < 0.001). Patients with a longer duration of respiratory illness tended to demonstrate smaller improvements in FEV₁ compared to those with a shorter disease duration (Table 5).

Figure 1 illustrates the relationship between duration of disease and improvement in FEV₁. The scatter plot demonstrates a downward trend, indicating that bronchodilator responsiveness gradually decreased with increasing duration of respiratory illness. Although individual variability was observed, the overall distribution of data points supports the presence of a modest but significant inverse correlation between disease duration and post-bronchodilator improvement in lung function.

Table 1. Demographic and Clinical Characteristics of the Study Participants (n = 135)

Table 2. Comparison of Pulmonary Function Parameters Before and After Bronchodilator Therapy (n = 135)

Table 3. Distribution of Patients According to Bronchodilator Responsiveness (n = 135)

Table 4. Comparison of Bronchodilator Response Between Asthma and COPD Patients

Table 5. Correlation Between Duration of Disease and Improvement in FEV₁ Following Bronchodilator Therapy

Figure 1: Correlation Between Duration of Disease and Improvement in FEV₁ Following Bronchodilator Therapy

The present study evaluated pulmonary function changes following bronchodilator therapy in patients with obstructive airway diseases and demonstrated significant improvements in all measured spirometric parameters. A substantial proportion of patients exhibited significant bronchodilator responsiveness, with a greater response observed among patients with bronchial asthma than among those with COPD. Additionally, a significant inverse relationship was identified between disease duration and improvement in FEV₁ following bronchodilator administration.

In the present study, significant increases were observed in FEV₁, FVC, FEV₁/FVC ratio, PEFR, and FEF₂₅–₇₅% after bronchodilator administration. These findings support the established role of bronchodilator therapy in improving airflow limitation and reducing airway resistance in obstructive airway diseases. Similar observations were reported by Alexis et al., who demonstrated that bronchodilator administration resulted in measurable improvements in spirometric indices and highlighted the importance of pulmonary function testing in assessing treatment response [7]. Likewise, Gong et al. reported that post-bronchodilator changes in FEV₁ remain clinically valuable for evaluating airway reversibility in chronic respiratory disorders [8].

The present study found that 65.9% of patients demonstrated significant bronchodilator responsiveness. This observation is consistent with contemporary evidence suggesting that bronchodilator responsiveness is common across obstructive airway diseases, although its magnitude varies considerably among individuals. Beasley et al., in a large multinational cohort, reported that positive bronchodilator responses were observed across asthma and COPD populations and emphasized that responsiveness should be viewed as a continuum rather than an absolute diagnostic characteristic [9].

A notable finding of the present study was the significantly higher prevalence of bronchodilator responsiveness among patients with bronchial asthma compared with those with COPD. This observation is biologically plausible because airway obstruction in asthma is generally more reversible owing to variable bronchoconstriction and airway hyperresponsiveness. Lázár et al. demonstrated that treatment-naïve patients with asthma exhibited greater bronchodilator responsiveness than patients with COPD irrespective of the assessment criteria used, supporting the findings of the present study [10].

Although bronchodilator responsiveness was more frequent among asthma patients, nearly half of the COPD patients in the present study also demonstrated significant reversibility. Similar findings have been reported in recent literature. Han et al. observed that bronchodilator responsiveness may occur in tobacco-exposed individuals with or without COPD and may reflect distinct physiological characteristics rather than a separate disease entity [11]. Furthermore, Alobaidi et al. demonstrated that significant bronchodilator responses can also be detected in small-airway function among patients with COPD, highlighting the heterogeneity of airflow limitation in this population [12].

The present study also demonstrated a significant negative correlation between disease duration and improvement in FEV₁. Patients with longer disease duration exhibited comparatively smaller gains in pulmonary function following bronchodilator administration. Progressive airway remodeling, chronic inflammation, and structural changes occurring over time may contribute to reduced reversibility of airflow obstruction. These findings are supported by studies suggesting that chronic disease progression is associated with diminished bronchodilator responsiveness and increasing fixed airflow limitation [11,12].

Recent investigations comparing different definitions of bronchodilator responsiveness have further emphasized the importance of spirometric assessment in clinical practice. Solanus de la Serna et al. reported that the prevalence of bronchodilator responsiveness varies according to the criteria applied, although spirometric evaluation remains indispensable for identifying patients who derive measurable functional benefit from bronchodilator therapy [13].

The present study demonstrated that bronchodilator therapy produced significant improvements in pulmonary function parameters, including FEV₁, FVC, FEV₁/FVC ratio, PEFR, and FEF₂₅–₇₅% among patients with obstructive airway diseases. A substantial proportion of patients exhibited significant bronchodilator responsiveness, with reversibility being more pronounced in individuals with bronchial asthma than in those with COPD. Furthermore, a significant negative correlation was observed between disease duration and improvement in FEV₁, suggesting that prolonged disease may be associated with reduced responsiveness to bronchodilator therapy. These findings highlight the value of spirometric assessment in monitoring treatment response and emphasize the potential benefits of early diagnosis and timely therapeutic intervention in patients with obstructive airway disorders.

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