Severe traumatic brain injury is a serious and ever growing issue of public health and the social economy of the World. It comprises 10% of all brain injuries and contributes to the high proportion of disabilities and deaths (McGarry et al., 2002; Mosenthal et al., 2002). STBI has a high mortality rate with prolonged hospital stay on average 17.5 days (Tagliaferri et al., 2006). The 14-day mortality on average remained 30.2%and most patients died in 48 hours (Braun CT, 2015). In the United States, approximately 235,000 patients were treated in the hospital per year due to traumatic brain injury (TBI). The estimated annual death rate in the US is about 50,000 cases per annum, with 21 to 400 billion US dollar annual costs due to TBI(Corrigan, Selassie and Orman, 2010; Marin, Weaver and Mannix, 2017). The annual cost of hospitalization due to traumatic brain injury (TBI) in China was 800 billion US dollars, with a mortality rate 9.8% (Liet al., 2015).

The complete recovery of a patient of STBI to pre-injury level is uncommon. Approximately 60% of the patient has ongoing impairment in the area of cognitive competency, gross motor activity, and recreational activity (Dikmen et al., 2003). Patients with STBI can have airway obstruction, aspiration, and hypoxia (Jovanovic et al., 2015). Mechanical ventilation is indicated in many patients with severe TBI(Jovanovic et al., 2015; Li et al., 2015). It maintains the oxygenation, protects airways, and maintains respiration. Most of the patients about 80% wean of early within 7 days from the mechanical ventilation without a respiratory problem, once the acute physiological disorder is corrected. However, 20% of patients still require prolonged mechanical ventilation after 7 days (Hess and MacIntyre, 2011). During the first four days, ventilator-associated pneumonia occurs in about 60% of the patients with severe traumatic brain injury (Ensault et al., 2017). The early systemic inflammatory response to head trauma patients predispose to early-onset VAP (Hedrick TL et al., 2008), while late-onset VAP that occurs after five days of mechanical ventilation (MV) is caused mainly by drug-resistant bacteria (Garnacho-Montero et al., 2014). Patients on mechanical ventilation have high morbidity, mortality, and infection rate due to acute respiratory distress syndrome and pulmonary embolism from venous thromboembolism (Nair and Niederman, 2015).

They also have decreased consciousness levels, disrupted natural defense barriers, decreased mobility, and lack of ability to protect the airways which can lead to pulmonary complications. Data is limited about effect of VAP in patients with STBI outcome. However multi organ failure has been identified as an independent contributor of poor outcomes in patients with severe TBI(Zygun et al., 2005).

A simple tool for the diagnosis of VAP was needed, thus a scoring system was developed in 1991, which included 7 clinical parameters for VAP diagnosis and it was named as Clinical Pulmonary Infection Score (CPIS) (Pugin J. Et al 1991) . The diagnosis of VAP was made using body temperature, leukocyte count and morphology, the character of tracheal secretion, PaO2 / FiO2 ratio, presence of pulmonary infiltration and its progression and microbiological culture results. A score of 6 or more suggests VAP (Basyigit. 2017).

Bronchoalveolar Lavage (BAL) is a minimally invasive procedure done with instillation of normal saline into subsegments of the lung followed by suction and collection of the instilled fluid for analysis. Loftus et al concluded in their study in 2017 that over half of all intubated patients with head or chest injury had evidence of pneumonia on Early Bronchoalveolar Lavage (E-BAL) performed within 48 hours of admission. E-BAL was associated with early discontinuation of antibiotics (7.3 vs 9.2 days), fewer days on mechanical ventilation (10.5 vs 16), fewer tracheostomies (49% vs 75%) and shorter ICU length of stay compared to L-BAL triggered by clinical suspicion of pneumonia (12 vs 17days). So, they found E-BAL useful for intubated patients with TBI or chest trauma. But the effect of this early lavage on severity of VAP assessed on CPIS is lacking. This study will help in determining the effect of early bronchoalveolar lavage on VAP in ventilated moderate and severe traumatic brain injury patients and will reflect the effect of early bronchoalveolar lavage on VAP through CPIS which can serve as prognostic indicator.