Chronic Obstructive Pulmonary Disease (COPD) is an irreversible respiratory illness that gets increasingly worse over time, which is defined by incessant limitation of airflow reduction, commonly linked to increased sensitivity to corrosive particles or gases within the lungs. The World Health Organization records COPD as the third cause of death in the world, yet this is a major challenge to its health [1]. The incidence and outcomes of acute exacerbations of COPD (AECOPD) that include a rapid deterioration of respiratory conditions, including dyspnea, increase of the sputum amount, and its purulence, are one of the highest causes of hospitalization, costs of healthcare interventions, and a faster rate of fall in lung capacities [2]. In the course of AECOPD, acute respiratory failure, especially type 2 (hypercapnic) respiratory failure, may develop in a few patients under the influence of the combination of the increased work of breathing and the poor alveolar ventilation. These episodes increase the risk of morbidity and mortality if they are not managed efficiently. Traditionally invasive mechanical ventilation (IMV) is the primary mode of treatment in such cases. Nevertheless, IMV comes with various complications which include ventilator-associated pneumonia, barotrauma, adverse effects of sedation, and ICU stay [3]. The use of Non-Invasive Ventilation (NIV), administered mostly through Bi-level Positive Airway Pressure (BiPAP), has transformed the course of ventilator management of AECOPD with respiratory failure. NIV offers ventilatory support, but does not require endotracheal intubation, and assists in the reduction of work of breathing, increased gas exchange, the treatment of respiratory acidosis, and the relief of dyspnea [4]. A number of randomized controlled trials and meta-analyses showed that early implementation of NIV in properly identified COPD patients can reduce the risk of intubation, decrease time spent in ICU and hospitalization, and minimize the level of mortality [5,6]. NIV has especially proven to be effective among those with moderate to severe acidosis (pH<7.35) and hypercapnia (PaCO2 >45mm Hg). NIV success also relies on a careful patient selection process coupled with careful monitoring and timely escalation to invasive ventilation in cases of failure. The factors which predict poor outcomes in NIV are those with severe hypoxemia, altered sensorium, hemodynamic instability, and failure to show clinical improvement within the first few hours of therapy [7]. Although NIV is strongly recommended in AECOPD, its outcomes may differ, depending on the patient profile, time of ventilation, comorbidities, and local practice. It is therefore very important to constantly evaluate and report the usefulness of NIV in various clinical conditions in order to inform decision making regarding such therapies and to enhance outcomes. This research study was done to determine the clinical and physiological NIV outcomes in patients who were admitted with acute exacerbation of COPD. The research is dedicated to the evaluation of the changes in the respiratory indicators, indices of blood gases, intubation, hospitalization, length of stay in ICU, and mortality.

This prospective observational study was done in the Department of Respiratory Medicine and Intensive Care Unit (ICU), Rajiv Gandhi Institute of Medical Sciences (RIMS), Adilabad. Institutional Ethical approval was obtained for the study. Written consent was obtained from all the participants of the study after explaining the nature of the study in vernacular language.

Inclusion Criteria

1. Patients aged ≥ 40 years.
2. Confirmed diagnosis of COPD based on GOLD criteria.
3. Acute exacerbation with type 2 respiratory failure (pH < 7.35 and PaCO₂ > 45 mmHg).
4. Conscious, cooperative, and hemodynamically stable patients eligible for NIV.

Exclusion Criteria

1. Hemodynamic instability requiring vasopressors.
2. Severe encephalopathy (GCS < 8).
3. Inability to protect airway or excessive secretions.
4. Facial trauma, recent upper GI surgery, or contraindications to mask ventilation.
5. Immediate need for endotracheal intubation.

Sample Size: A total of 50 patients diagnosed with AECOPD and requiring NIV were included based on the inclusion and exclusion criteria.  All patients were initiated on Bi-level Positive Airway Pressure (BiPAP) using an oronasal mask connected to a dedicated NIV machine. Initial settings were IPAP (Inspiratory Positive Airway Pressure) of 10–14 cm H₂O and EPAP (Expiratory Positive Airway Pressure) of 4–6 cm H₂O. Settings were titrated based on clinical response and arterial blood gas (ABG) results. Patients were monitored for respiratory rate, heart rate, blood pressure, and oxygen saturation. ABG parameters (pH, PaCO₂, PaO₂, HCO₃⁻) at baseline, 2 hours, 6 hours, and 24 hours after NIV initiation. Level of consciousness using the Glasgow Coma Scale (GCS). Clinical signs of improvement (reduction in dyspnea, respiratory rate, use of accessory muscles).  The primary outcome parameters evaluated were improvement in ABG parameters and avoidance of endotracheal intubation (NIV success). Secondary outcomes estimated duration of NIV therapy, Length of ICU and hospital stay, and mortality.

Statistical Analysis: All the available data were segregated, refined, and uploaded to an MS Excel spreadsheet and analysed by SPSS version 25 in Windows format. The continuous variables were expressed as mean, standard deviation, and frequency. Categorical variables were calculated by Chi-square test, and values of p-value < 0.05 were considered statistically significant.

Based on the inclusion and exclusion criteria, a total of 50 cases were studied in the duration of our study. Table 1 depicts the baseline demographic characteristics of the cases included in the study. The mean age of the cohort was 68.4 years, with a male predominance (64%). Maximum cases were in advanced stages of COPD, and 56% were in stage III and 44% in stage II, based on Gold Staging. The baseline arterial blood gas (ABG) analysis showed respiratory acidosis and hypoxemia, and the mean pH was 7.28, PaCO₂ of 68.4 mmHg, and PaO₂ of 48.6 mmHg. The level of bicarbonates was elevated at (31.2 mmol/L), which occurs due to chronic compensation. The average respiratory rate was high, showing acute respiratory distress in the cases.

The patients included in the study were put on Non-Invasive Ventilation (NIV). The ABG parameters were recorded after NIV initiation, given in Table 2. A critical analysis of the table shows that there is a progressive improvement in ABG parameters following NIV. There was a significant increase in pH from 7.28 to 7.38 over 24 hours, showing correction of respiratory acidosis (p<0.001). Similarly, PaCO₂ significantly decreased from 68.4 to 52.3 mmHg, and PaO₂ improved from 48.6 to 78.4 mmHg (p<0.001). Although HCO₃⁻ showed a modest decline over time (p=0.07), indicating minimal renal compensation. This shows that NIV was able to rapidly improve gas exchange and acid-base correction in acute COPD exacerbations.

                          *Significant

The primary outcome of NIV therapy in the cohort is depicted in Table 3. A critical analysis of the table shows that NIV was successful in 42 out of 50 patients (84%), helping them avoid intubation. However, in 8(16%) cases NIV failed and required invasive mechanical ventilation. Among the cases which failed after NIV therapy, worsening ABG parameters were the most common cause (62.5%), followed by altered mental status (25%) and difficulty managing secretions (12.5%). These findings show that NIV therapy was effective in the majority of cases; however, close monitoring is required for identifying early signs of failure and further management.

Table 4 represents clinical and secondary results of NIV therapy. The mean duration of NIV was 48.6 hours; ICU stay was 4.2 days, and mean overall hospitalization was 8.6 days. The mortality was low, with a result of 6%. A major clinical benefit was recorded: respiratory rate decreased significantly (p<0.001) at 6 hours, 82% of subjects experienced improvements in dyspnea, and there was a GCS increase in 14.2 to 14.8 (p=0.003). These gains prove that NIV not only has benefits of improving physiological values but also leads to a quick symptomaticُ improvement in addition to an improved neurological condition.

In this table, significant variables among patients who responded to NIV and non-responders were compared. Failure NIV was correlated with worse acidosis (PH 7.22 and 7.30), elevated PaCO₂ (78.6 and 65.8 mmHg), and a larger percentage of GOLD Stage IV patients (87.5 and 35.7%), which were all significant. Failure was also predicted by elevated baseline rates of respiration, and delay in the normalization of pH at 2 hours. The failure group had significant hospital stay and mortality when compared to the success group (12.4 days with 37.5% mortality vs. 7.9 days and 0%, respectively), proving the usefulness of early ABG and clinical parameters in prognosis.

Over the last decade, non-invasive ventilation (NIV) has become an essential component of treatment for acute exacerbation of chronic obstructive pulmonary disease (AECOPD), especially in patients with acute respiratory acidosis and hypercapnia. In this study, with 50% of patients having moderate or severe exacerbations of COPD, NIV led to notable clinical and biochemical improvement in most patients with an 84% success rate. Such results correlate with past research, which indicates success rates of between 70% and 90% in well-chosen patients in AECOPD under NIV treatment [1, 2]. In our cohort, the mean age was 68.4 years, and male predominance, which coincides with the well-known demography of COPD [3]. The majority of patients were in the GOLD stage III or IV, which indicates more progressive disease. Participants had typical characteristics of acute-on-chronic respiratory failure at baseline, which showed low pH, high PaCO2, and low PaO2. With NIV initiation, a significant improvement was found in pH, PaCO2, and PaO2 at different intervals (2, 6, and 24 hours), which means respiratory acidosis was successfully reversed and the alveolar ventilation improved. These findings confirm the physiological efficacy of NIV in improving gas exchange and decreasing the work of breathing [4, 5]. In this study, in 84% of the cases, there was successful application of NIV, circumvented endotracheal intubation, and thus had the potential to omit development of ventilator-related infections and a decreased duration in ICU. The most common reasons that led to failure in the NIV undertaking among the 16 percent of all participants were failure in worsening the ABG value, lack of consciousness, and the inability to remove secretion. These results support earlier studies that indicated the presence of similar predictors of NIV failure [6,7]. Interestingly, there was an imbalance of Linear Scaled Statistics of pH, PaCO2, and prevalence of GOLD Stage IV among the failure group. Such factors need to be found early so that when the need arises, invasive mechanical ventilation can be escalated.

In our study, we successfully managed cases of acute exacerbation of chronic obstructive pulmonary disease (AECOPD), in 84% of cases, thereby avoiding endotracheal intubation and potentially reducing ventilator-associated complications and ICU stay. Among the 16% of cases who did not respond to NIV, the primary causes were worsening ABG values, decreased consciousness, and inability to clear secretions. The findings of our study were in agreement with other similar studies done in the past, where they reported similar predictors of NIV failure [6, 7]. We also found that the patients in the NIV failure group had significantly lower baseline pH, higher PaCO2, and most of them were in GOLD stage IV classification. Therefore, early identification of these predictors must be done in order to escalate to invasive mechanical ventilation when required. The analysis of secondary outcomes in this study shows the utility of NIV. We found rapid clinical improvement, including reduction in respiratory rate and dyspnea scores and modest improvement in GCS scores. These improvements show the tolerability and comfort of NIV in alert and co-operative patients, supporting the previous results from a meta-analysis [8]. In addition, the low hospital mortality (6%) and relatively short duration of ICU (4.2 days) and hospital stay (8.6 days) respectively suggest that NIV can lead to favourable clinical outcomes when used in appropriate cases. The comparison of NIV success and failure groups shows that the parameters such as low baseline pH, high PaCO₂, GOLD stage IV disease, and slower improvement in pH after 2 hours of NIV application are significant predictors of NIV failure. Therefore, these markers must be assessed routinely during NIV application as a guide for ongoing management, and based on these, the cases may be required to escalate with endotracheal intubation if parameters do not improve [9]. Although our study provides important aspects of NIV outcomes in our cohort, the limitations of the study were due to its small sample size and single-center design. Therefore, large-scale multicentric studies with larger cohorts will help to refine patient selection criteria.

Within the limitations of the current study, we found that Non-invasive ventilation (NIV) is a highly effective and safe intervention for managing acute exacerbations of chronic obstructive pulmonary disease (AECOPD) in patients with respiratory acidosis and hypercapnic respiratory failure. The results of this study showed that NIV achieved a success rate in 84% of cases, leading to rapid improvement in clinical and arterial blood gas parameters. We also found that in cases of NIV success, the duration of ICU stay was short and lower mortality. Failure in NIV was associated with higher GOLD stage, lower baseline pH, and higher PaCO2. Accurate and early identification of these parameters can help in refining the selection of patients and guide timely escalation to invasive ventilation if required.

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