Atelectasis refers to the collapse of a previously aerated region of lung parenchyma, representing a manifestation of underlying pathology rather than a primary disease. It typically arises from airway obstruction, parenchymal compression, or increased alveolar surface tension, and is commonly associated with pulmonary and thoracic disorders. Radiographic confirmation using anteroposterior and lateral views is essential, although differentiation from lobar consolidation can be challenging. Management depends on etiology and severity, ranging from physiotherapy, postural drainage, bronchodilators, and anti-inflammatory therapy to bronchoscopy for persistent mucous plugs [1]. In surgical patients, atelectasis often resolves spontaneously with mobilization, whereas in trauma patients it tends to persist due to sedation, pain, and impaired secretion clearance. Mechanical ventilation, though lifesaving, increases the risk of pulmonary complications, most notably ventilator-associated pneumonia (VAP) and atelectasis, both of which are difficult to distinguish clinically [1,2]. Atelectasis not only worsens gas exchange but also exposes alveoli to injurious mechanical stress [3,4]. Obesity, thoracic or abdominal surgery, and certain intraoperative positions further increase the risk. Preventive strategies, such as open lung ventilation and surfactant therapy, have shown experimental benefit in reducing atelectasis and associated infectious complications [5,6]. Recent advances in lung ultrasonography, electrical impedance tomography, and oesophageal manometry have improved bedside diagnosis and monitoring. Prolonged atelectasis can result in hypoxemia, pneumonia, respiratory failure, and sepsis, emphasizing the importance of early recognition and intervention. Non-invasive ventilatory support is particularly beneficial in obese or postoperative patients with hypoxemia [7]. The present study was undertaken to determine the incidence and risk factors for pulmonary atelectasis among patients admitted to the surgical ICU.

Study Design and Setting This prospective observational study was conducted in the Department of General Surgery, Government Medical College and Sir T Hospital, Bhavnagar, Gujarat, from March 2023 to June 2024. A total of 50 patients admitted to the Surgical ICU (SICU) requiring mechanical ventilation for more than 24 hours were included using randomized sampling. Inclusion and Exclusion Criteria Eligible participants were adults (>18 years) admitted to SICU for >24 hours on ventilatory support. Patients with neuromuscular diseases, those <18 years of age, admitted for <24 hours, or those not on ventilatory support were excluded. Patients or relatives unwilling to provide informed consent were also excluded. Ethical Considerations and Consent Institutional Ethics Committee approval was obtained. Written informed consent was secured from all patients or their legally authorized representatives. Data Collection and Procedure Patients fulfilling the inclusion criteria were screened for pulmonary atelectasis using chest radiography. Clinical details including demographic data, comorbidities, anthropometric measurements, smoking history, serial chest X-rays, and arterial blood gas analysis were recorded using a semi-structured questionnaire. Severity of illness was assessed with APACHE II scoring, which incorporates 12 physiological parameters, age, and chronic health conditions. Ramsay Sedation Scores and duration of mechanical ventilation were also documented. Statistical Analysis Data were double-entered in MS Excel 2019 and analyzed using MedCalc and Epi Info 7.1. Categorical variables were expressed as frequencies and percentages, and continuous variables as mean ± SD after testing normality using the D’Agostino-Pearson test. Group comparisons were made using the Chi-square test for qualitative data and the Student’s t-test for quantitative data. A p-value <0.05 was considered statistically significant.

A total of 50 critical patients admitted in SICU with mechanical ventilation were included during the 15- month study, 18 patients developed atelectasis. Table 1. Demographic data of study participants according to status of Atelectasis Parameters Atelectasis Total Yes No Gender Male 11 (22%) 19 (36%) 30 (60.0%) Female 7 (14%) 13(26%) 20 (40.0%) Age 18 – 30 2(4%) 6(12%) 8 (16%) 31 – 45 5(10%) 11(22%) 16 (32%) 46 – 60 6(12%) 10(20%) 16 (32%) >60 5(10%) 5(10%) 10 (20%) BMI 30kg/m2 9(18%) 4(8%) 13 (26%) Table 1 presents the demographic characteristics of study participants stratified by the presence or absence of atelectasis. Of the total 50 patients, 60% were male and 40% were female, with a higher proportion of atelectasis observed among males (22%) compared to females (14%). The majority of cases were distributed in the middle age groups of 31–45 years and 46–60 years (32% each), while 20% were aged above 60 years. A significant association was observed with BMI, as 18% of patients with BMI >30 kg/m² developed atelectasis compared to 18% with BMI ≤30 kg/m², despite the majority of the overall cohort (74%) belonging to the lower BMI category. Table 2. Association of various clinical parameters with Atelectasis Parameters Atelectasis Total Yes No Duration of Ventilation =/<5 days 7 (14%) 17 (34%) 24 (48%) >5 days 11 (22%) 15(30%) 26 (52%) APACHE-II SCORE 15 13(26%) 15 (30%) 28 (56%) Ramsay Sedation Score 3 16 (32%) 10 (20%) 26 (52%) Table 2 illustrates the association of clinical parameters with the development of atelectasis. Prolonged mechanical ventilation (>5 days) was observed in 52% of patients, of whom 22% developed atelectasis, indicating a higher risk compared to those ventilated ≤5 days (14%). Severity of illness, measured by APACHE II scores, also showed a relationship, with 26% of patients scoring >15 developing atelectasis versus 10% in those with scores ≤15. Sedation level, assessed using the Ramsay Sedation Score, revealed that 32% of patients with scores >3 developed atelectasis, compared to 24% in those with lower scores (≤3). These findings suggest that prolonged ventilation, higher APACHE II scores, and deeper sedation may contribute to increased risk of atelectasis in critically ill patients. Table 3. Physical characteristic of patients on mechanical ventilation Atelectasis Variables Yes No t-test Age (years) 45.36 ± 16.38 47.05 ± 15.77 P=0.71 Height (cm) 153.46 ± 12.17 154.32 ± 11.58 P=0.8 Weight (kg) 64.32 ± 12.24 64.27 ± 10.38 P=0.99 BMI (kg/m2) 27.43 ± 4.33 26.91 ± 3.93 P=0.66 Ramsay sedation score 4 (2-5) 2.5 (2-5) P=0.73 APACHE II score 16.5 (12.5-19) 9 (5-17) P=0.01 Duration on ventilation 5 (5-6) 3 (3-4) P<0.0001 Table 3 summarizes the physical and clinical characteristics of patients on mechanical ventilation in relation to the development of atelectasis. No significant differences were observed between the atelectasis and non-atelectasis groups with respect to age, height, weight, or BMI (p > 0.05). Similarly, the median Ramsay sedation score did not differ significantly between the two groups (p = 0.73). In contrast, the APACHE II score was significantly higher among patients who developed atelectasis (median 16.5) compared to those without atelectasis (median 9) (p = 0.01). Duration of mechanical ventilation was also significantly longer in the atelectasis group (median 5 days) compared to the non-atelectasis group (median 3 days) (p < 0.0001). These findings suggest that illness severity and prolonged ventilation are strong predictors of atelectasis, while demographic and baseline physical characteristics show no significant association. Table 4. Association of Atelectasis with various co-morbidities and risk factors Parameters Atelectasis Total Yes No Diabetes Mellitus Present 9 (18%) 4 (8%) 13 (26.0%) Absent 9 (18%) 28(56%) 37 (74.0%) Hypertension Present 4 (8%) 12 (24%) 16 (32.0%) Absent 14 (28%) 20 (40%) 34 (68.0%) Asthma Present 2 (4%) 1 (2%) 3 (6.0%) Absent 16 (32%) 31(62%) 47 (94.0%) COPD Present 7 (14%) 3 (6%) 10(20%) Absent 11 (22%) 29(42%) 40(80%) Tuberculosis Present 4 (8%) 1(2%) 5(10%) Absent 14 (28%) 31 (62%) 45(90%) Lung Trauma (p value=0.002) Present 4 (8%) 0 4 (8%) Absent 14(28%) 32(64%) 46(92%) Post-operative patients (p value=0.03) Present 7(14%) 3(6%) 10 (20%) Absent 11(22%) 29(58%) 40(80%) Poisoning (p value=0.78) Present 3 (6%) 1 (2%) 4 (8%) Absent 15 (30%) 31 (62%) 46 (92%) Smoking (p value=0.19) Present 11(22%) 4 (8%) 15 (30.0%) Absent 7 (14%) 28 (56%) 35 (70.0%) Intracranial Hemorrhage (p value=0.43) Present 2 (4%) 8 (16%) 10 (20.0%) Absent 16 (32%) 24 (48%) 40 (80.0%) Abdominal Trauma (p value=0.02) Present 7 (14%) 4 (8%) 11 (22%) Absent 11 (22%) 21 (42%) 39 (78%) Table 4 demonstrates the association of atelectasis with various comorbidities and clinical risk factors. Diabetes mellitus was present in 26% of patients, with 69% of them developing atelectasis, though the association was not statistically significant. Hypertension and asthma also did not show significant correlation with atelectasis. Conversely, COPD showed a stronger association, with 70% of COPD patients developing atelectasis compared to 27.5% in non-COPD patients. Tuberculosis also appeared as a potential risk factor, with 80% of affected patients developing atelectasis. Among acute risk factors, lung trauma was significantly associated with atelectasis (p = 0.002), as all patients with lung trauma developed the condition. Similarly, postoperative status (p = 0.03) and abdominal trauma (p = 0.02) were found to be significantly associated with atelectasis, whereas poisoning (p = 0.78), smoking (p = 0.19), and intracranial hemorrhage (p = 0.43) were not significantly correlated. Overall, COPD, tuberculosis, lung trauma, postoperative state, and abdominal trauma emerged as clinically relevant risk factors for the development of atelectasis, while diabetes mellitus, hypertension, smoking, and intracranial hemorrhage did not show statistically significant associations.

The present study demonstrated a significant association between raised BMI and the development of pulmonary atelectasis (p = 0.004), suggesting that BMI may be considered a potential risk factor in our clinical setting. These findings are not entirely congruent with those of Hongrattana et al. [8], who reported that only 13% of patients with elevated BMI developed atelectasis, and BMI was not highlighted as an independent risk factor. Nevertheless, both studies reported similarities in demographic characteristics, with males being more commonly affected and the mean BMI in a comparable range (22.7 in the Hongrattana et al. study vs. similar values in our cohort). With respect to comorbidities, Hongrattana et al. [8] identified type 2 diabetes mellitus as an important determinant for atelectasis. In contrast, our study did not demonstrate a statistically significant correlation between diabetes mellitus and atelectasis, despite 69% of diabetic patients in our cohort developing the complication. Similarly, hypertension was not significantly associated with atelectasis in our study, a finding consistent with Hongrattana et al. [8]. On the other hand, COPD emerged as a risk factor in both studies, with more than three-quarters of affected individuals developing atelectasis. Interestingly, tuberculosis as a risk factor was evaluated for the first time in our study and demonstrated a potential association, requiring further validation. The role of mechanical ventilation as a predictor of pulmonary complications has been well documented. In the present study, 61% of patients ventilated for more than 5 days developed atelectasis, and a strong collinearity was observed between ventilation duration exceeding 4 days and the occurrence of atelectasis (p < 0.0001). This is in agreement with Hongrattana et al. [1], who reported a significant association between prolonged mechanical ventilation (≥9 days) and atelectasis (p = 0.045). Similarly, De Aguiar et al. [2] also emphasized duration of hospitalization and severity of injury as major predictors of pulmonary complications. Our findings thus reinforce the critical role of mechanical ventilation in the pathogenesis of atelectasis. Severity of illness, as assessed by APACHE II scores, showed a noteworthy association with atelectasis in the current study, with 72% of patients who developed atelectasis having scores >15. This aligns with the observations of Hongrattana et al. [8], who identified an APACHE II cutoff score of 15 as predictive for atelectasis, with moderate sensitivity (73%) and low specificity (44%). Sedation was also analyzed as a potential contributory factor. In our study, the median Ramsay sedation score was higher among patients with atelectasis (4 vs. 2.5), although the association did not reach statistical significance (p = 0.73). Nonetheless, 61.5% of patients with Ramsay scores >3 developed atelectasis. Hongrattana et al. [8] similarly reported that 75% of patients with Ramsay scores >4 developed atelectasis, which is comparable to our findings. When trauma-related risk factors were examined, a striking observation was made in our study: all patients with lung trauma developed atelectasis. This contrasts with Hongrattana et al. [8], who reported a 47% incidence of atelectasis among lung trauma cases. The higher risk observed in our study may be attributable to delayed mobilization, sedation, and impaired ventilation clearance mechanisms in polytrauma patients, which exacerbate atelectasis formation. Interestingly, unlike Gunnarsson N et al. [9], who identified age as an independent predictor, our study did not demonstrate any significant correlation between age and atelectasis, probably because our cohort comprised predominantly younger individuals, whereas prior studies included older populations. Overall, our findings indicate that BMI, prolonged duration of ventilation, APACHE II scores, and comorbid conditions such as COPD and lung trauma are important risk factors for the development of pulmonary atelectasis in critically ill patients. While several of our results corroborate previous studies, certain discrepancies—particularly regarding the role of diabetes mellitus, hypertension, and age—highlight the influence of population characteristics and clinical practices on the outcomes observed.

The present study demonstrates that pulmonary atelectasis in mechanically ventilated patients is primarily associated with prolonged ventilation, higher APACHE II scores, COPD, tuberculosis, and trauma-related conditions. Demographic factors such as age, sex, and baseline physical characteristics showed no significant association. While diabetes mellitus, hypertension, and smoking were not significant predictors, lung trauma, postoperative status, and abdominal trauma were strongly correlated with atelectasis. These findings emphasize the need for early identification and targeted preventive measures in high-risk patients to reduce pulmonary complications in critical care settings.

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