European Journal of Cardiovascular Medicine

Respiratory failure is frequent and severe organ dysfunction occurring in the intensive care unit (ICU).[i] Under this circumstance, invasive or non-invasive mechanical ventilations (MV) are life-sustaining interventions.[ii] However, despite significant advances in ventilatory support[iii], it remains associated with elevated mortality[iv] and a significant impairment in the patients’ quality of life in the post-ICU setting.[v] Therefore, information about the epidemiological aspects of patients under mechanical ventilation is important from both clinical and health policy perspectives. Intensive care itself is a resource intensive setting and has to be used judicially and ventilator care further adds on the cost of care. On an average in intensive care units around 33% patients received mechanical ventilation for a mean (SD) duration of 5.9 ± 7.2 days.[vi]

Acute respiratory failure is the most frequent reason for the initiation of mechanical ventilation which occurs in acute respiratory distress syndrome (ARDS), pneumonia, acute pulmonary edema, congestive heart failure, sepsis, trauma, aspiration, postoperative, toxin inhalation, acute exacerbation of COPD and other acute episodes.[vii]

A growing population of patients (5% to 10%) survive acute critical illness only to become chronically critically ill (CCI) with profound weakness and ongoing respiratory failure.⁶ The most perceptible feature of this group is their prolonged dependence on mechanical ventilation (7% to 15% of intensive care unit patients).⁷ Repeated episodes of sepsis are the hallmark of the CCI, and possibly contribute to lengthened ICU stay. There is some controversy about who should be considered a CCI patient.

Commonly observed complications in patients on ventilator support are acute respiratory distress syndrome (ARDS), ventilator associated pneumonia (VAP), sepsis, shock, multiple organ failure syndrome (MODS), acute renal failure (ARF), hepatic failure, coagulopathy and GI hemorrhage. Nosocomial infection is major cause of morbidity and mortality among patients admitted in ICUs and VAP occurred in 10% to 25% in patients on ventilatory support with 33% to 50% mortality rate.[viii]

Survival among mechanically ventilated patients depends not only on the factors present at the start of mechanical ventilation, but also on the development of complications and patient management in the intensive care unit.[ix] Overall mortality rate among patients at intensive care unit was found around 30.7% and survival of patients who required ventilatory supports more than 12 hours was found to be around 69%.⁹ This information about the mortality is useful for better counseling of patients and their families. It can help to evaluate the outcome in patients receiving mechanical ventilation for specific indications.⁹

Comprehensive information about the clinical characteristics, outcomes and risk factors for mortality of patients requiring ventilator support is essential to assist clinicians in the decision-making process and to allow better resource allocation.[x]

Our objective was to describe the indications, clinical course, complications, and the outcomes of this subgroup of ICU patients who required ventilatory supports.

The study was a hospital-based, observational study conducted over a 12-month period from April 2014 to March 2015 at the Medical Intensive Care Unit (MICU) of Northern Railway Central Hospital, New Delhi. The cohort consisted of 99 patients requiring invasive mechanical ventilation for over 12 hours. Key parameters such as length of stay, duration of ventilatory support, clinical course, complications, and outcomes were assessed.

Informed consent was obtained from the patient’s relatives after appropriate counseling regarding the patient’s condition and prognosis. Ethical approval for the study was obtained from the Institutional Ethics Committee, and the study protocol was approved by the Scientific Committee of Northern Railway Central Hospital.

Patients eligible for the study were those requiring invasive ventilation for over 12 hours, based on the criteria for mechanical ventilation: Type I respiratory failure (PaO2 < 60 mm Hg with normal or low PaCO2) and Type II respiratory failure (PaCO2 > 50 mm Hg with PaO2 < 60 mm Hg, with or without pH < 7.3). Infants and patients who expired within 12 hours of ventilation were excluded.

Patient data were collected through a structured proforma, capturing detailed history and clinical examination. Diagnosis upon admission was based on clinical findings and supported by relevant investigations, including arterial blood gas (ABG) analysis, chest X-rays, and electrocardiograms (ECG). Comorbidities, such as hypertension, diabetes, and chronic conditions (e.g., renal or liver disease, COPD), were recorded, along with lifestyle factors like smoking and alcohol consumption, which could affect the patient's clinical course.

Disease severity was assessed using the APACHE II score, which incorporates physiological parameters, age, and chronic health conditions. The worst physiological values in the first 24 hours were used to calculate the score. The Glasgow Coma Score (GCS) was also employed to evaluate neurological status. Chronic health conditions, including liver cirrhosis, class IV angina, chronic hypoxemia, and renal failure, were recorded for outcome prediction.

The length of hospital stay was recorded from admission to discharge or death, and the duration of ventilatory support was defined as the period from the initiation of ventilation to the onset of weaning. Complications related to ventilatory support and ICU stay were assessed. The final outcome of each patient, either survival or death, was documented.

Data were managed and analyzed using SPSS version 17.0. Continuous variables were presented as mean ± SD, while categorical variables were presented as absolute numbers and percentages. Student’s t-test was used to compare normally distributed continuous variables between groups, and the Chi-squared test or Fisher’s exact test was employed for comparing nominal categorical data. A p-value of <0.05 was considered statistically significant.

Out of 99 patients, there were 37 (37.4%) female and 62 (62.6%) male patients. The mean age of patients was 64.35 years with standard deviation (SD) of 11.23 years. Minimum age was 34 years and maximum age was 89 years. (Figure 1) Out of 99 patients, there were 25 (25.3%) pneumonia, 15 (15.2%) neurological, 10 (10.1%) non-pulmonary sepsis, 15 (15.2%) acute on chronic respiratory failure (COPD / Asthma), 10 (10.1%) cardiogenic / hypovolemic shock, 11 (11.1%) cardiogenic pulmonary edema, 3 (3.0%) aspiration and 10 (10.1%) others cases.(Figure 2) Out of 99 patients, 69 (69.7%)  had HTN, 63 (63.6%) had T2DM, 10 (10.1%) had hypothyroidism, 25 (25.3%) had CKD (chronic kidney disease), 5 (5.1%) had CLD (chronic liver disease), 52 (52.5%) had respiratory comorbid conditions,  49 (49.5%) had cardiac comorbid conditions, 10 (10.1%) had CNS comorbid conditions, 5 (5.1%) had malignant conditions, 8 (8.1%) was chronic alcoholic, 38 (38.4%) was smoker / tobacco chewer and 7 (7.1%) had other comorbid conditions.(Table 1) Apache II score was calculated with in first 24 hours of admission to access severity and predict outcome of patients at intensive care unit. Mean apache II score was 28.30 with SD of 11.93.

Figure 1:Age distribution of patients

Figure 2:Distribution of diagnosis on admission

Table 1:Distribution of comorbid conditions in patients

The mean duration of on ventilator days was 9.64 days with SD of 5.95. The range of on ventilator days was 2 days to 27 days. The mean duration of hospital stay (days) was 20.38 days with SD of 10.07. (Table 2) Out of 99 patients, 27 (27.3%) developed ARDS, 32 (32.3%) developed ventilator associated pneumonia (VAP), 50 (50.5%) developed sepsis, 30 (30.3%) developed shock, 33 (33.3%) developed acute renal failure (ARF), 5 (5.1%) developed multiorgan dysfunction (MODS), 20 (20.2%) developed UTI and 14 (14.1%) developed gastrointestinal (GI) bleeding. (Figure 3)

Table 2:Distribution of hospital stay (days) in patients

Figure 3:Distribution of complication in patients

Out of 99 patients, 6 (6.1%) required BIPAP, 6 (6.1%) required SIMV, 9 (9.1%) required CMV, 31 (31.3%) required CMV followed by SIMV, 37 (37.4%) required SIMV followed by BIPAP and 10 (10.1%) required CMV followed by SIMV followed by BIPAP mode of ventilator. (Table 3)

Table 3:Distribution of mode of ventilator in patients

Out of 99 patients, 45 (45.5%) survived after invasive ventilatory support for more than 12 hours and 54 (54.5%) died during invasive ventilatory support. The mean age of survived patients was 59.64 years with SD of 11 and mean age of dead patients was 68.28 years with SD of 11.35 years. Maximum mortality was 90.9% in 81 to 90 years age group. This result was found statistically significant (p<0.05).

The mean age of survived patients was 59.64 years with SD of 11 and mean age of dead patients was 68.28 years with SD of 11.35 years. Maximum mortality was 90.9% in 81 to 90 years age group. This result was found statistically significant (p<0.05).(Table 4)  Comparison of mortality among male (53.2%) and female (56.8%) study group did not show much difference. This result was found statistically non-significant (p>0.05). (Table 5)  Patients having more than one comorbid conditions together and comparison between cluster of comorbid conditions and mortality showed that increase in number of mortality associated with high mortality. This result was found statistically significant (p<0.05). (Table 6) Out of 99 patients, 45 survived with apache II score in between 11 to 30, and 54 died with apache II score in between 11 to 60. The median score of survived was 19 with IQR (Interquartile range) of 15.0-22.25 and median score of died was 35 with IQR of 28-42.25. Comparison of mortality among different apache II score groups showed that more than 30 apache II score had high mortality around of 100%. This result was found statistically significant (p<0.05). Out of 99 patients, 45 survived with median 6.5 days (IQR = 4.0-9.25) and 54 died with median 11.5 days (IQR = 6.0-16.0) (table 19). Maximum mortality 100% was found in patients with more than 15 days of duration on ventilator stay. This result was found statistically significant (p<0.05). Out of 99 patients, 45 survived with median duration of hospital was 19 days and IQR of 11.50-26.50 and 54 died with median duration of hospital was 20 days and IQR of 11.75-30. Maximum mortality 92.3% was found in patients with more than 30 days duration of hospital stay. This result was found statistically significant (p<0.05). (Table 7)  Out of 99 patients, 27 had ARDS with 92.6% (n=25) mortality, 32 had ventilator associated pneumonia (VAP) with 53.15% (n=17) with mortality, 50 had sepsis with 66.0% (n=33) mortality, 30 had shock with 73.3% (n=22) mortality, 33 had ARF with 63.6% (n=21) mortality, 5 had MODS with 100% (n=5) mortality, 20  had UTI with 40.0% (n=8) mortality, 14 had UGI bleeding with 71.4% (n=10) mortality. From this result ARDS, sepsis, shock and MODS were found statistically significant (p<0.05). (Table 8) Out of 99 patients, 6 required BIPAP with 0% (n=0) mortality, 6 required SIMV with 100% (n=6) mortality, 9 required CMV with 100% (n=9) mortality, 31 required CMV followed by SIMV with 100% (n=31) mortality, 37 required SIMV followed by BIPAP with 0.0% (n=0) mortality and 10 required on CMV followed by SIMV followed by BIPAP with 80% (n=8) mortality. This result was found statistically significant (p<0.05). (Table 9)

Table 4:Comparison of mean age with mortality

Table 5:Comparison of mortality with gender

Table 6:Comparison between cluster of comorbid conditions with mortality

Table 7:Median, IQR and P Value with Apache 2 score, duration of hospital stay (days) and on ventilator days in between survived and dead patients

Table 8:Comparison of complications with mortality

Table 9:Comparison of mode of ventilator with mortality

The present study provides valuable insights into the clinical characteristics, outcomes, and complications among patients requiring invasive mechanical ventilation (MV) in an intensive care setting. Consistent with previous research, respiratory failure was the most frequent indication for MV, with Type I and Type II respiratory failures being prominent.[i] In our cohort, pneumonia (25.3%) and neurological conditions (15.2%) were the leading causes of respiratory failure, corroborating findings from the literature, where conditions such as ARDS, sepsis, and neurological disorders were reported as major indications for ventilation distribution in this study, with a predominance of male patients (62.6%), is in line with earlier studies that showed a higher frequency of MV in males . Additionally, age (64.35 years) was slightly higher compared to other studies where the mean age ranged from 53.9 to 59.2 years.¹⁰ The higher mortality observed in particularly those aged 81–90 years (90.9%), underscores the increased vulnerability of elderly patients, which has been consistently reported in the literature.[ii] .

The study's mortality rate of 54.5% is comparable to other studies, which have reported figures between 30% and 60% depending on the underlying pathology and severity of illness.[iii] Notably, conditions such as ARDS (92.6% mortality) and sepsis (66% mortality) were adverse outcomes in our study, reflecting global trends where these complications are recognized as significant contributors to mortality in ventilated patients. The present study also confirmed the association between non-pulmonary organ failure, such as acute renal failure, a finding well-documented in existing literature.[iv]

The APACHE II score was a strong predictor of mortality in our study, with a median score of 35 among non-survivors, which is consistent with higher APACHE II scores as predictive of poor outcomes. Patients with a score higher than 30 had a near-100% mortality rate, emphasizing the prognostic value of this scoring system in critically ill patients.

Complications related to mechanical ventilation, including ventilator-associated pneumonia (32.3%), acute renal failure (33.3%), and sepsis (50.5%), were observed frequently. The rates of these complications are consistent with previous studies, which have reported VAP rates ranging from 9.8% to 25%, with corresponding mortality rates of 33% to 50% . The present study found a significant association between complications such as ARDS, MODS, and sepsis with increased mortality, similar to findings from studies by Esteban et al.uration of ventilatory support and hospital stay were also significant predictors of mortality. Patients requiring ventilation for more than 15 days had a 100% mortality rate, and those with hthan 30 days had a mortality rate of 92.3%. These findings align with the literature, where prolonged mechanical ventilation and extended ICU stays have been associated with worse outcomes. Moreover, modes of ventilation played a critical role in patient outcomes, with patients receiving non-invasive modes such as BIPAP having a 0% mortality rate, while invasive modes like CMV were associated with higher with prior studies emphasizing the risks of invasive mechanical ventilation.[v]

In conclusion, the findings of this study reinforce the critical role of early intervention, the management of complications, and the use of predictive scoring systems like APACHE II in improving outcomes for patients on mechanical ventality associated with complications such as ARDS and sepsis, as well as the impact of prolonged ventilation and higher APACHE II scores, highlight the need for targeted therapeutic strategies to mitigate these risks and improve survival rates

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