European Journal of Cardiovascular Medicine

Acute respiratory failure (ARF) is a common and life-threatening condition encountered in critical care units worldwide. It is characterized by the inability of the respiratory system to maintain adequate gas exchange, resulting in hypoxemia and/or hypercapnia. ARF may arise due to diverse etiologies such as pneumonia, chronic obstructive pulmonary disease (COPD) exacerbations, acute respiratory distress syndrome (ARDS), cardiogenic pulmonary edema, and other critical illnesses [1]. Timely and appropriate respiratory support is crucial to improve patient outcomes and reduce morbidity and mortality associated with this condition.

Mechanical ventilation is a cornerstone of supportive therapy in ARF. Traditionally, invasive mechanical ventilation (IMV) via endotracheal intubation has been the mainstay treatment for severe respiratory failure. However, IMV is associated with various complications including ventilator-associated pneumonia (VAP), airway trauma, sedation-related adverse effects, and prolonged ICU stay [2]. These risks have prompted the evolution and increased utilization of non-invasive ventilation (NIV) techniques that deliver ventilatory support without the need for endotracheal intubation.

Non-invasive ventilation involves the delivery of positive pressure ventilation through a mask interface, thereby avoiding the complications associated with invasive airway management. NIV has gained widespread acceptance as an effective treatment modality for selected patients with ARF, particularly in those with exacerbations of COPD, cardiogenic pulmonary edema, and certain cases of hypoxemic respiratory failure [3]. Multiple randomized controlled trials and meta-analyses have demonstrated the benefits of NIV in reducing the need for intubation, lowering ICU length of stay, and improving survival in appropriate patient populations [4].

Despite these advantages, NIV is not universally applicable and may fail in certain clinical scenarios, necessitating transition to invasive mechanical ventilation. Identifying patients who will benefit most from NIV and monitoring for early signs of failure are critical components in the management of ARF. Moreover, the decision to initiate NIV or IMV depends on clinical judgment, patient factors, and resource availability. Therefore, comparative studies evaluating the outcomes of NIV versus IMV in medical ICU settings provide valuable insights for optimizing respiratory care [5].

Aim

To compare the clinical outcomes of non-invasive ventilation versus invasive mechanical ventilation in medical ICU patients with acute respiratory failure.

Objectives

1. To assess and compare the duration of ventilatory support between patients receiving non-invasive ventilation and those receiving invasive mechanical ventilation.
2. To evaluate and compare the rates of complications, including ventilator-associated pneumonia and other adverse events, in both groups.
3. To analyze the ICU length of stay and mortality outcomes among medical ICU patients managed with non-invasive versus invasive ventilation.

Source of Data: Data for this study were obtained from medical records and ICU monitoring charts of patients admitted to the Medical Intensive Care Unit (MICU) at tertiary care teaching hospital.

Study Design: This was a retrospective observational cross-sectional study comparing outcomes of patients managed with non-invasive ventilation (NIV) versus invasive mechanical ventilation (IMV).

Study Location: The study was conducted in the Medical Intensive Care Unit.

Study Duration: Data collection and analysis covered a period of 18 months, from March 2023 to September 2024.

Sample Size: A total of 200 patients with acute respiratory failure requiring ventilatory support were included, divided equally into two groups of 100 patients each receiving NIV and IMV respectively.

Inclusion Criteria:

·         Patients aged ≥18 years admitted to MICU with a diagnosis of acute respiratory failure.

·         Patients who received either non-invasive ventilation or invasive mechanical ventilation as primary ventilatory support.

·         Patients with documented clinical and laboratory data during ICU stay.

Exclusion Criteria:

·         Patients who received both NIV and IMV during the same ICU admission.

·         Patients with incomplete medical records or missing key clinical data.

·         Patients with neuromuscular disorders or terminal illnesses where ventilatory support was provided for palliative purposes.

Procedure and Methodology: Eligible patients were identified from ICU admission logs and ventilator records. Relevant demographic, clinical, and laboratory data were extracted, including baseline characteristics, underlying diagnosis, ventilation parameters, duration of ventilation, complications, length of ICU stay, and mortality. Patients were categorized into two groups based on the type of ventilation received: NIV group and IMV group. Standard ICU protocols for ventilatory management, sedation, infection control, and supportive care were followed as per hospital guidelines during the study period.

Sample Processing: Data were anonymized and entered into a secured database for statistical analysis. Quality checks were performed to ensure data accuracy and completeness.

Statistical Methods: Descriptive statistics such as mean, standard deviation, median, and interquartile ranges were calculated for continuous variables. Categorical variables were expressed as frequencies and percentages. Comparisons between NIV and IMV groups were made using Student’s t-test or Mann-Whitney U test for continuous variables and Chi-square test or Fisher’s exact test for categorical variables. A p-value <0.05 was considered statistically significant. Statistical analysis was performed using SPSS version 25.0 (IBM Corp., Armonk, NY, USA).

Data Collection: Data collection was performed by trained research assistants using a structured proforma. Ethical approval was obtained from the Institutional Ethics Committee prior to study initiation, and patient confidentiality was maintained throughout the study.

Table 1: Baseline Demographic and Clinical Characteristics of Patients (N=200)

*Significant

In this study of 200 medical ICU patients with acute respiratory failure, baseline demographic and clinical characteristics were comparable between the non-invasive ventilation (NIV) and invasive mechanical ventilation (IMV) groups. The mean age of patients in the NIV group was 58.3 ± 14.8 years, while the IMV group had a slightly higher mean age of 60.7 ± 15.6 years, though this difference was not statistically significant (t = 1.28, 95% CI: -1.18 to 6.03, p = 0.203). Gender distribution was similar across both groups, with males constituting 61.0% in the NIV group and 66.0% in the IMV group (χ² = 0.52, p = 0.472). Regarding primary diagnoses, COPD exacerbation was the most common, observed in 43.0% and 41.0% of the NIV and IMV groups respectively, followed by pneumonia and cardiogenic pulmonary edema; none of these differences reached statistical significance. However, the severity of illness as assessed by the APACHE II score was significantly higher in the IMV group (20.2 ± 6.3) compared to the NIV group (17.4 ± 5.6), with a mean difference reflected by a t value of 3.67 (95% CI: -4.20 to -1.34, p = 0.0004), indicating a greater baseline acuity among invasively ventilated patients.

Table 2: Duration of Ventilatory Support in NIV and IMV Groups (N=200)

*Highly significant

When comparing the duration of ventilatory support, the NIV group required significantly shorter ventilation, averaging 42.6 ± 18.7 hours, in contrast to 91.8 ± 34.2 hours in the IMV group (t = 13.4, 95% CI: -56.9 to -44.3, p < 0.0001). This notable difference underscores the less invasive nature and quicker weaning potential of NIV in suitable patients.

Table 3: Complications during Ventilatory Support in NIV and IMV Groups (N=200)

     *Significant

Regarding complications, ventilator-associated pneumonia (VAP) occurred significantly less frequently in the NIV group, affecting only 7.0% of patients compared to 29.0% in the IMV group (χ² = 17.9, p < 0.0001). Similarly, barotrauma was observed in 3.0% of NIV patients versus 12.0% of IMV patients (χ² = 7.24, p = 0.0072), and tracheal injury occurred exclusively in the IMV group (8.0%, χ² = 10.0, p = 0.0016). Nosocomial infections other than VAP were more common in the IMV group (18.0%) than in the NIV group (10.0%), though this difference did not reach statistical significance (χ² = 2.65, p = 0.103). These findings highlight the higher risk profile of invasive ventilation related complications.

Table 4: ICU Length of Stay and Mortality Outcomes in NIV and IMV Groups (N=200)

         *Highly significant

ICU length of stay and mortality outcomes also favored the NIV group. Patients receiving NIV had a significantly shorter ICU stay, with a mean duration of 7.4 ± 3.1 days compared to 13.6 ± 5.4 days in the IMV group (t = 13.7, 95% CI: -7.38 to -5.27, p < 0.0001). ICU mortality was considerably lower in the NIV group at 15.0%, while the IMV group had a mortality rate of 34.0% (χ² = 11.9, p = 0.0006). These highly significant differences reflect the potential survival benefit and reduced healthcare resource utilization associated with non-invasive ventilation in appropriately selected patients.

The baseline demographic and clinical characteristics (Table 1) show that the NIV and IMV groups were generally comparable in terms of age and gender distribution, with no statistically significant differences observed (p=0.203 and p=0.472, respectively). This aligns with prior studies such as Mas A et al. (2014)[6] and Liu YJ et al. (2016)[7], who similarly reported matched baseline characteristics when comparing NIV and IMV cohorts in acute respiratory failure . The primary diagnoses across both groups predominantly included COPD exacerbations, pneumonia, cardiogenic pulmonary edema, and ARDS, reflecting common etiologies of respiratory failure in ICU settings. This diagnostic profile concurs with the patient populations described by Scala R. (2016)[8] and Luo F,et al. (2017)[9], who emphasized COPD and pneumonia as frequent indications for ventilatory support.

Notably, the APACHE II scores were significantly higher in the IMV group (20.2 ± 6.3) compared to the NIV group (17.4 ± 5.6) (p=0.0004), indicating greater illness severity in invasively ventilated patients. This finding is consistent with Hidalgo V et al. (2015)[10], who observed that patients requiring IMV often present with higher acuity and worse physiological derangements. The higher baseline severity likely contributes to the differences in outcomes between the two groups.

Table 2 demonstrates a highly significant reduction in the duration of ventilatory support among NIV patients (42.6 ± 18.7 hours) compared to IMV patients (91.8 ± 34.2 hours) (p < 0.0001). This shorter ventilation duration in NIV aligns with systematic reviews by Navarra SM et al. (2020)[11] and Bourke SC et al. (2018)[12], which highlight NIV’s advantage in reducing ventilation time and facilitating earlier weaning. The less invasive nature of NIV may contribute to faster recovery of respiratory function and decreased sedation requirements, as also suggested by Romero-Dapueto C et al. (2015)[13].

Complications related to ventilation (Table 3) were significantly higher in the IMV group. Ventilator-associated pneumonia (VAP) occurred in 29.0% of IMV patients versus only 7.0% in the NIV group (p < 0.0001). Barotrauma and tracheal injury were similarly more frequent in IMV patients, consistent with the well-documented risks of endotracheal intubation and positive pressure ventilation Stefan MS et al. (2015)[14]. These findings mirror the results of Gacouin A et al. (2015)[15], who reported significantly increased infectious and mechanical complications in invasively ventilated patients compared to NIV. The absence of significant difference in non-VAP nosocomial infections suggests that the overall infection risk may not differ substantially outside the direct complications related to airway management.

Table 4 highlights that ICU length of stay and mortality were significantly lower in the NIV group. The mean ICU stay was nearly halved in the NIV group (7.4 ± 3.1 days) compared to IMV (13.6 ± 5.4 days) (p < 0.0001), and mortality was reduced from 34.0% in IMV patients to 15.0% in the NIV cohort (p = 0.0006). These results are supported by meta-analyses such as those by Burns KE et al. (2014)[16] and Singh G et al. (2014)[17], demonstrating that NIV reduces ICU length of stay and mortality in selected patients with acute respiratory failure. The improved survival and shorter hospitalization associated with NIV likely reflect both its avoidance of complications and the treatment of patients with relatively lower illness severity.

In this study comparing non-invasive ventilation (NIV) and invasive mechanical ventilation (IMV) in medical ICU patients with acute respiratory failure, NIV was associated with significantly shorter duration of ventilatory support, lower rates of ventilator-associated complications, reduced ICU length of stay, and decreased mortality compared to IMV. Although patients receiving IMV had higher baseline severity of illness, the findings underscore the efficacy and safety of NIV as a first-line ventilatory strategy in appropriately selected patients. Early application of NIV can minimize invasive-related complications and improve overall clinical outcomes, thereby reducing healthcare resource utilization. These results support the preferential use of NIV in suitable acute respiratory failure cases to optimize patient prognosis.

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