hospital - acquired pneumonia ( hap ) is one of the most common nosocomial infections and the leading cause of death due to hospital - acquired infections ( attributable to mortality 33 - 50% ) . among hap patients , vap is the most common icu ( intensive care unit)-acquired infection in patients requiring mechanical ventilation for over 48 hours and its estimated incidence is 10 - 20% . the crude icu mortality rates for vap range from 24 to 76% , and these patients are twice as likely to die as those patients on ventilator without pneumonia . other than being an independent determinant of mortality ; vap is associated with longer icu and hospital stays , prolonged mechanical ventilation , and higher costs . in the recent past , various advancements have taken place in the management of vap . several studies have provided important insights into the relationship of the histology and bacteriology of vap , various epidemiological researches have allowed the establishment of concepts for empiric antimicrobial treatment , and various updates on state - of - the - art care have been outlined . however , despite these measures , a majority of issues related to the management of vap remain unresolved and are subject to controversy . the lack of consensus regarding the best way to diagnose vap largely explains why the incidence rates vary so widely from one study to another  from 5 to 50% of mechanically ventilated intensive care unit ( icu ) patients . the keywords ,  ventilator - associated pneumonia, in pubmed revealed a total of 2474 titles and 521 review articles within the search limit of 10 years , between 1990 and 2010 . only articles in english , vap was diagnosed on the presence of new and / or progressive pulmonary infiltrates on a chest radiograph , plus two or more of the following criteria : fever (  38.5c ) or hypothermia ( < 36c ) , leucocytosis (  12  109 / l ) , purulent tracheobronchial secretions or a reduction of partial pressure of arterial oxygen ( pao2 ) / fraction of inspired oxygen ( fio2 ) of 15% or greater , in the past 48 hours . as per the same guidelines , tracheobronchitis was defined as the presence of purulent tracheobronchial secretions plus two or more of the following criteria : fever (  38.5c ) or hypothermia ( < 36c ) , leucocytosis (  12  109 / l ) or significant bacteriological counts in the respiratory secretions of patients without pulmonary infiltrates suggesting pneumonia on chest radiograph . cases with either vap or tracheobronchitis had to be microbiologically confirmed . however , according to a more recent criteria , vap is defined as pneumonia occurring in a patient within 48 hours or more after intubation , with an endotracheal tube or tracheostomy tube , which was not present before . early onset of vap occurs within 48 hours and late onset of vap after 48 hours of tracheal intubation and mechanical ventilation . there are several factors that potentially contribute to the high rates of vap in icu patients . first , icus contain clusters of highly vulnerable patients , many of whom have predisposing lung conditions that compromise with the defense mechanisms in their airways . although the respiratory tract is designed to prevent the entry of pathogenic organisms into the lungs and to eradicate such pathogens if they bypass the upper airway host defenses , these defense mechanisms can be overwhelmed at times , for example , a large aspirated inoculum or an inherently virulent organism . aspiration is promoted by supine position and by upper airway and nasogastric tube placement . in mechanically ventilated patients , aspiration occurs around the outside of the endotracheal tube rather than through the lumen . given that as many as 45% of the healthy individuals aspirate during sleep , it is understandable that aspiration is even more common among patients with abnormal swallowing , impaired gag reflexes , compromised consciousness due to medication or anesthesia , delayed gastric emptying , or decreased gastric motility . these bacteria presumably reach the lower airway via aspiration of gastric contents or of upper airway secretions . oropharyngeal colonization with gram - negative bacilli is unusual in otherwise healthy , non - hospitalized individuals . in moderately ill patients , however , the carriage rate is around 16% , rising to almost 75% in severely ill patients . thus , the propensity for colonization of the upper airway directly correlates with the severity of illness . in addition to the severity of illness , several other factors have been identified as being associated with gram - negative colonization , as shown in table 1 . risk factors for vap following gram - negative sepsis in critically ill patients other means by which pneumonia can be acquired include aspiration from the stomach or nose and paranasal sinuses . aspiration of the gastric contents can be minimized by maintaining the patient in a semi - recumbent position , but this is not an effective measure for minimizing oropharyngeal aspiration . the most crucial task in vap is to arrive at an early diagnosis . this is often difficult because many conditions common to icu patients like sepsis , acute respiratory distress syndrome ( ards ) or pulmonary atelectasis may present with a similar clinical picture . it has been seen in some studies that more than 50% of the diagnosed patients do not have vap and up to one - third of the patients may remain undiagnosed . the diagnosis of vap is usually based on three components : systemic signs of infection , new or worsening infiltrates seen on the chest x - ray , and bacteriological evidence of pulmonary parenchymal infection . the systemic signs of infection , such as , fever , tachycardia , and leukocytosis , are nonspecific findings and can be caused by any condition that releases cytokines . although the plain ( usually portable ) chest x - ray remains an important component in the evaluation of hospitalized patients with suspected pneumonia , it is most helpful when it is normal and rules out pneumonia . in a review of 24 patients with autopsy - proven pneumonia , who were receiving mechanical ventilation ( mv ) , the presence of air bronchograms was the only sign that corresponded well with pneumonia , accurately predicting a majority of the diagnosed cases of pneumonia . found that the clinical predictions of the presence or absence of definite and probable vap were accurate in 62 and 84% of vap patients , respectively . in another study assessing the clinical criteria for vap in surgical patients , numerous clinical parameters distinguished patients with suspected vap from others however , the subsequent validation of this diagnosis by serial examination of clinical , microbiological , and radiographic data could not identify the predictors of patients truly having vap . the controversy about the clinical diagnosis of vap chiefly included the role of the clinical criteria in the assessment of suspected vap . although some authors have advocated an approach relying strictly on the results of invasive bronchoscopic diagnostic testing , others have insisted on an approach that keeps the clinical and microbiological criteria in balance , not withholding antimicrobial treatment in the presence of cultures below the thresholds , but clinically suspected vap . although the limited diagnostic accuracy does not undermine the importance of clinical assessment , according to a large body of evidence derived from several validation studies , using strictly independent references , invasive and noninvasive microbiological testing ie also associated with 30 - 40% false - negative and false - positive results . a recommended approach to the clinical diagnosis of vap is the clinical pulmonary infection score ( cpis ) , which was developed by pugin et al . this score includes the following six weighted clinical and microbiological variables : temperature , white blood cell count , character and volume of the tracheobronchial aspirate , gram stain and culture of the tracheobronchial aspirate , gas exchange ratio , and chest radiograph infiltrates [ table 2 ] . this score proved to achieve 72% sensitivity and 85% specificity at a threshold of six in a postmortem study . clinical pulmonary infection score ( cpis ) calculation for vap a meta - analysis , including 23 studies of quantitative bronchoalveolar lavage ( bal ) , and a review of 18 studies evaluating quantitative protective specimen brush ( psb ) confirmed the excellent diagnostic utility of these methods . to minimize the false negative rate ( 10 - 40% ) , sampling should be performed prior to any antibiotic change in the preceding 24 to 72 hours . patients with negative quantitative bal cultures collected prior to the antibiotic changes can have empiric antibiotics safely discontinued after 72 hours . several guidelines integrate the clinical and microbiological criteria in a diagnostic algorithm to institute prompt empiric therapy in patients with a high suspicion for hospital - acquired pneumonia ( hap ) and tailor therapy based on the reassessment of the clinical response and quantitative culture results . there has been lot of speculation about the possible usefulness of the biological markers in vap . c - reactive protein ( crp ) and cytokine measurements in the serum or bal of vap patients have been tried , without any success . the role of serum procalcitonin as a prognostic marker was evaluated in an observational study with 63 vap patients . those who failed treatment had higher procalcitonin levels from days one to seven . a prospective study involving 96 icu patients revealed the serum procalcitonin to be 100% specific for vap , but not very sensitive ( 41% ) . a prospective cohort study of 75 patients with clinical suspicion of vap showed similar results . non - survivors had significantly higher serum procalcitonin levels on days zero and four , and the decrease in levels by day four was predictive of survival ( or 4.43 , p0.04 ) . triggering receptor expressed on myeloid cells-1 ( trem-1 ) is a promising biomarker of pneumonia as well as vap - related sepsis . trem-1 belongs to the immunoglobin superfamily and is expressed on the surface of neutrophils , monocytes , and macrophages , during acute inflammatory responses . it increases during infectious processes , but not in inflammatory conditions ( e.g. , psoriasis , ulcerative colitis , vasculitis ) . trem-1 exists in both a membranous and a soluble form ( soluble triggering receptor expressed on myeloid cells-1 ; strem-1 ) . elevated levels of strem-1 have been detected in the plasma of septic patients ; in the bal of patients with pneumonia , and in the exhaled breath condensate in vap patients . in a recent study of vap - related sepsis , the serum strem-1 levels remained elevated from days one to seven in non - survivors compared to serum cytokines . another finding was that decreased ratios of strem-1 / tnfa seemed to identify the progression from sepsis to septic shock . studies strongly support the potential role of alveolar strem-1 as a diagnostic biomarker for vap and an indicator of the clinical outcomes . a commercially available assay is unavailable and a high alveolar strem-1 does not preclude airway sampling and microbiological cultures to isolate the causative organism for pneumonia . the routine use of prolonged courses of antibiotics , not supported by the results of microbiological cultures , should be discouraged , to minimize the risk of subsequent antibiotic - resistant infections . elimination of unnecessary antibiotic administration for a prolonged period can reverse the trend of increasing antibiotic resistance among hospital - acquired infections . the use of aerosolized antibiotics has also been discouraged because of the inefficacy and propensity for the emergence of antibiotic - resistant infections . the routine use of selective digestive tract decontamination ( sdd ) has also not gained acceptance because of its lack of demonstrated effect on the mortality , emergence of antibiotic resistance infections , and additional toxicity . moreover , some clinicians had a particular concern about the risk of infection with clostridium difficile , as a result of sdd . as the mortality rate for patients with vap on inadequate antibiotics treatment is also high ( 69.2 versus 46.0% if they are on the right antibiotics ) , individual icus should develop empirical antibiotic policies targeting the pathogenic bacteria prevalent in their patient population . antibiotic discontinuation policies ( based on noninfectious causes for chest radiograph infiltrates and signs and symptoms suggesting that vap has resolved ) have been shown to reduce the antibiotic treatment duration without a significant deleterious effect on hospital mortality or recurrence of vap . a further curtailment of the multi - resistant bacteria may be possible with the rotation of antibiotics , particularly for gram - negative bacilli . over a seven - year period , antibiotic rotation for empirical and therapeutic use was associated with a reduction in the vap rate ( 23% before versus 16.3% following antibiotic rotation introduction ) and an increase in the susceptibility of gram - negative organisms to the antibiotics commonly used . fowler et al . treated 156 patients with suspected vap and showed that patients who received empiric therapy with anti - pseudomonal penicillins plus beta - lactamase inhibitors had lower in - hospital mortality than those who did not receive these antibiotics . retrospectively examined the microbiological sensitivities of 140 patients with vap and determined that sulbactam and cefoperazone were the most appropriate antibiotics . if staphylococcal pneumonia was suspected , a glycopeptide ( vancomycin or teicoplanin ) or combined trimethoprim - sulfamethoxazole was recommended , until the sensitivity results were obtained . therefore , a targeted approach with an appropriate dose of the right antibiotic guided by evidence , as has been suggested in the tarragona strategy , is one of the logical approaches for vap [ table 3 ] . several measures to prevent vap have proven to be effective and are generally recommended . the euro - nis study ( moro and jepsen ) has described different practices that may reduce exogenous infections due to better surveillance and better staff education.2)hand - washing and disinfection : these are the most important measures to prevent patient to patient spread of pathogens , as well as to protect healthcare workers from potential infections.3)change of the ventilator circuit not more than once per week : daily change of ventilator circuits was shown to be a risk factor for vap . although the optimal exchange interval has not been determined , a policy of circuit change once a week as compared to a 48-hour interval has been shown to be safe.4)orotracheal instead of nasotracheal intubation : nasotracheal intubation increases the risk for sinusitis and vap . therefore , orotracheal intubation should be the preferred technique.5)keeping the endotracheal tube cuff pressure optimized : the pressure of the endotracheal tube cuff should be optimized in order to prevent the leakage of colonized subglottic secretions into the lower airways.6)semi - recumbent body position : a reduction of aspiration into the lower airways , in a semi - recumbent versus a supine body position , has been shown by scinitgraphic means . moreover , the effect of a semi - recumbent position on the reduction of vap has been demonstrated.7)avoidance of paralytic medication : deeply sedated and relaxed patients clearly are at a higher risk of aspiration and vap . therefore , relaxation should be avoided whenever possible.8)avoidance of reintubation : reintubation was clearly demonstrated to represent a risk factor for vap . furthermore , it seems obvious that non - invasive ventilation instead of intubation should reduce the incidence of vap , particularly in patients who are immunocompromised.9)a meta - analysis examining 33 randomized sdd ( selective digestive decontamination ) trials involving 5,727 patients , demonstrated a significant reduction in the overall mortality ( 20% ) and in the incidence of respiratory tract infections ( 65% ) . a second systematic review in critically ill surgical patients showed an even greater benefit of sdd : mortality was reduced by 30% and the rates of pneumonia by 80% . sdd may be used in subsets of populations , such as , patients with trauma , pancreatitis , major burn injury , and those undergoing major elective surgery and transplantation . precautions of pathogen transmission from patient to patient , including isolation . the euro - nis study ( moro and jepsen ) has described different practices that may reduce exogenous infections due to better surveillance and better staff education . hand - washing and disinfection : these are the most important measures to prevent patient to patient spread of pathogens , as well as to protect healthcare workers from potential infections . change of the ventilator circuit not more than once per week : daily change of ventilator circuits was shown to be a risk factor for vap . although the optimal exchange interval has not been determined , a policy of circuit change once a week as compared to a 48-hour interval has been shown to be safe . orotracheal instead of nasotracheal intubation : nasotracheal intubation increases the risk for sinusitis and vap . therefore , orotracheal intubation should be the preferred technique . keeping the endotracheal tube cuff pressure optimized : the pressure of the endotracheal tube cuff should be optimized in order to prevent the leakage of colonized subglottic secretions into the lower airways . semi - recumbent body position : a reduction of aspiration into the lower airways , in a semi - recumbent versus a supine body position , has been shown by scinitgraphic means . moreover , the effect of a semi - recumbent position on the reduction of vap has been demonstrated . avoidance of paralytic medication : deeply sedated and relaxed patients clearly are at a higher risk of aspiration and vap . avoidance of reintubation : reintubation was clearly demonstrated to represent a risk factor for vap . furthermore , it seems obvious that non - invasive ventilation instead of intubation should reduce the incidence of vap , particularly in patients who are immunocompromised . a meta - analysis examining 33 randomized sdd ( selective digestive decontamination ) trials involving 5,727 patients , demonstrated a significant reduction in the overall mortality ( 20% ) and in the incidence of respiratory tract infections ( 65% ) . a second systematic review in critically ill surgical patients showed an even greater benefit of sdd : mortality was reduced by 30% and the rates of pneumonia by 80% . sdd may be used in subsets of populations , such as , patients with trauma , pancreatitis , major burn injury , and those undergoing major elective surgery and transplantation . the department of health in the uk published the following  high impact interventions for ventilated patients in june 2007 . a)elevation of the head of bed to 35 - 40 degreesb)sedation holdingc)deep vein thrombosis prophylaxisd)gastric ulcer prophylaxise)appropriate humidification of inspired gasf)appropriate tubing managementg)suctioning of respiratory secretions ( including use of gloves and decontaminating hands before and after the procedure)h)routine oral hygiene as per local policy 
  elevation of the head of bed to 35 - 40 degrees deep vein thrombosis prophylaxis gastric ulcer prophylaxis appropriate humidification of inspired gas appropriate tubing management suctioning of respiratory secretions ( including use of gloves and decontaminating hands before and after the procedure ) routine oral hygiene as per local policy of all these interventions , elevation of the head , gastric ulcer prophylaxis , continuous suctioning of the subglottic secretions , chlorhexidine mouthwash , enteral feeding with a post - pyloric feeding tube , and daily sedation interruption are of particular importance to prevent vap . the nascent randomized trial explored the possibility of using a silver - coated endotracheal tube and found a statistically significant reduction in the incidence of vap and delayed time to vap when compared to a similar uncoated tube . although cost - effectiveness was a presumed hindrance , a more recent study has found that the silver - coated endotracheal tubes yielded persistent savings per case of vap prevented . many controversies still remain with regard to the epidemiology , diagnosis , prognosis , and therapy of ventilator - associated pneumonia . in particular , the proportion of ventilator - associated pneumonia that can be prevented by improving the quality of care is yet to be fully understood . to address these issues , a thorough understanding of the precise natural history of ventilator - associated pneumonia at a cellular level , and establishing the sequence of events between colonization and infection , is needed . till such time , vap will continue to present as a major therapeutic challenge to clinicians , particularly when patient management is complicated by the presence of underlying conditions . according to the previous definitions , vap was diagnosed on the presence of new and / or progressive pulmonary infiltrates on a chest radiograph , plus two or more of the following criteria : fever (  38.5c ) or hypothermia ( < 36c ) , leucocytosis (  12  109 / l ) , purulent tracheobronchial secretions or a reduction of partial pressure of arterial oxygen ( pao2 ) / fraction of inspired oxygen ( fio2 ) of 15% or greater , in the past 48 hours . as per the same guidelines , tracheobronchitis was defined as the presence of purulent tracheobronchial secretions plus two or more of the following criteria : fever (  38.5c ) or hypothermia ( < 36c ) , leucocytosis (  12  109 / l ) or significant bacteriological counts in the respiratory secretions of patients without pulmonary infiltrates suggesting pneumonia on chest radiograph . cases with either vap or tracheobronchitis had to be microbiologically confirmed . however , according to a more recent criteria , vap is defined as pneumonia occurring in a patient within 48 hours or more after intubation , with an endotracheal tube or tracheostomy tube , which was not present before . early onset of vap occurs within 48 hours and late onset of vap after 48 hours of tracheal intubation and mechanical ventilation . there are several factors that potentially contribute to the high rates of vap in icu patients . first , icus contain clusters of highly vulnerable patients , many of whom have predisposing lung conditions that compromise with the defense mechanisms in their airways . although the respiratory tract is designed to prevent the entry of pathogenic organisms into the lungs and to eradicate such pathogens if they bypass the upper airway host defenses , these defense mechanisms can be overwhelmed at times , for example , a large aspirated inoculum or an inherently virulent organism . aspiration is promoted by supine position and by upper airway and nasogastric tube placement . in mechanically ventilated patients , aspiration occurs around the outside of the endotracheal tube rather than through the lumen . given that as many as 45% of the healthy individuals aspirate during sleep , it is understandable that aspiration is even more common among patients with abnormal swallowing , impaired gag reflexes , compromised consciousness due to medication or anesthesia , delayed gastric emptying , or decreased gastric motility . third , the dominant organisms in nosocomial pneumonia are aerobic gram - negative bacilli . these bacteria presumably reach the lower airway via aspiration of gastric contents or of upper airway secretions . oropharyngeal colonization with gram - negative bacilli is unusual in otherwise healthy , non - hospitalized individuals . in moderately ill patients , however , the carriage rate is around 16% , rising to almost 75% in severely ill patients . thus , the propensity for colonization of the upper airway directly correlates with the severity of illness . in addition to the severity of illness , several other factors have been identified as being associated with gram - negative colonization , as shown in table 1 . risk factors for vap following gram - negative sepsis in critically ill patients other means by which pneumonia can be acquired include aspiration from the stomach or nose and paranasal sinuses . aspiration of the gastric contents can be minimized by maintaining the patient in a semi - recumbent position , but this is not an effective measure for minimizing oropharyngeal aspiration . this is often difficult because many conditions common to icu patients like sepsis , acute respiratory distress syndrome ( ards ) or pulmonary atelectasis may present with a similar clinical picture . it has been seen in some studies that more than 50% of the diagnosed patients do not have vap and up to one - third of the patients may remain undiagnosed . the diagnosis of vap is usually based on three components : systemic signs of infection , new or worsening infiltrates seen on the chest x - ray , and bacteriological evidence of pulmonary parenchymal infection . the systemic signs of infection , such as , fever , tachycardia , and leukocytosis , are nonspecific findings and can be caused by any condition that releases cytokines . although the plain ( usually portable ) chest x - ray remains an important component in the evaluation of hospitalized patients with suspected pneumonia , it is most helpful when it is normal and rules out pneumonia . in a review of 24 patients with autopsy - proven pneumonia , who were receiving mechanical ventilation ( mv ) , the presence of air bronchograms was the only sign that corresponded well with pneumonia , accurately predicting a majority of the diagnosed cases of pneumonia . found that the clinical predictions of the presence or absence of definite and probable vap were accurate in 62 and 84% of vap patients , respectively . in another study assessing the clinical criteria for vap in surgical patients , numerous clinical parameters distinguished patients with suspected vap from others however , the subsequent validation of this diagnosis by serial examination of clinical , microbiological , and radiographic data could not identify the predictors of patients truly having vap . the controversy about the clinical diagnosis of vap chiefly included the role of the clinical criteria in the assessment of suspected vap . although some authors have advocated an approach relying strictly on the results of invasive bronchoscopic diagnostic testing , others have insisted on an approach that keeps the clinical and microbiological criteria in balance , not withholding antimicrobial treatment in the presence of cultures below the thresholds , but clinically suspected vap . although the limited diagnostic accuracy does not undermine the importance of clinical assessment , according to a large body of evidence derived from several validation studies , using strictly independent references , invasive and noninvasive microbiological testing ie also associated with 30 - 40% false - negative and false - positive results . a recommended approach to the clinical diagnosis of vap is the clinical pulmonary infection score ( cpis ) , which was developed by pugin et al . this score includes the following six weighted clinical and microbiological variables : temperature , white blood cell count , character and volume of the tracheobronchial aspirate , gram stain and culture of the tracheobronchial aspirate , gas exchange ratio , and chest radiograph infiltrates [ table 2 ] . this score proved to achieve 72% sensitivity and 85% specificity at a threshold of six in a postmortem study . clinical pulmonary infection score ( cpis ) calculation for vap a meta - analysis , including 23 studies of quantitative bronchoalveolar lavage ( bal ) , and a review of 18 studies evaluating quantitative protective specimen brush ( psb ) confirmed the excellent diagnostic utility of these methods . to minimize the false negative rate ( 10 - 40% ) , sampling should be performed prior to any antibiotic change in the preceding 24 to 72 hours .   patients with negative quantitative bal cultures collected prior to the antibiotic changes can have empiric antibiotics safely discontinued after 72 hours . several guidelines integrate the clinical and microbiological criteria in a diagnostic algorithm to institute prompt empiric therapy in patients with a high suspicion for hospital - acquired pneumonia ( hap ) and tailor therapy based on the reassessment of the clinical response and quantitative culture results . there has been lot of speculation about the possible usefulness of the biological markers in vap . c - reactive protein ( crp ) and cytokine measurements in the serum or bal of vap patients have been tried , without any success . the role of serum procalcitonin as a prognostic marker was evaluated in an observational study with 63 vap patients . those who failed treatment had higher procalcitonin levels from days one to seven . a prospective study involving 96 icu patients revealed the serum procalcitonin to be 100% specific for vap , but not very sensitive ( 41% ) . a prospective cohort study of 75 patients with clinical suspicion of vap showed similar results . non - survivors had significantly higher serum procalcitonin levels on days zero and four , and the decrease in levels by day four was predictive of survival ( or 4.43 , p0.04 ) . triggering receptor expressed on myeloid cells-1 ( trem-1 ) is a promising biomarker of pneumonia as well as vap - related sepsis . trem-1 belongs to the immunoglobin superfamily and is expressed on the surface of neutrophils , monocytes , and macrophages , during acute inflammatory responses . it increases during infectious processes , but not in inflammatory conditions ( e.g. , psoriasis , ulcerative colitis , vasculitis ) . trem-1 exists in both a membranous and a soluble form ( soluble triggering receptor expressed on myeloid cells-1 ; strem-1 ) . elevated levels of strem-1 have been detected in the plasma of septic patients ; in the bal of patients with pneumonia , and in the exhaled breath condensate in vap patients . in a recent study of vap - related sepsis , the serum strem-1 levels remained elevated from days one to seven in non - survivors compared to serum cytokines . another finding was that decreased ratios of strem-1 / tnfa seemed to identify the progression from sepsis to septic shock . studies strongly support the potential role of alveolar strem-1 as a diagnostic biomarker for vap and an indicator of the clinical outcomes . a commercially available assay is unavailable and a high alveolar strem-1 does not preclude airway sampling and microbiological cultures to isolate the causative organism for pneumonia . the routine use of prolonged courses of antibiotics , not supported by the results of microbiological cultures , should be discouraged , to minimize the risk of subsequent antibiotic - resistant infections . elimination of unnecessary antibiotic administration for a prolonged period can reverse the trend of increasing antibiotic resistance among hospital - acquired infections . the use of aerosolized antibiotics has also been discouraged because of the inefficacy and propensity for the emergence of antibiotic - resistant infections . the routine use of selective digestive tract decontamination ( sdd ) has also not gained acceptance because of its lack of demonstrated effect on the mortality , emergence of antibiotic resistance infections , and additional toxicity . moreover , some clinicians had a particular concern about the risk of infection with clostridium difficile , as a result of sdd . as the mortality rate for patients with vap on inadequate antibiotics treatment is also high ( 69.2 versus 46.0% if they are on the right antibiotics ) , individual icus should develop empirical antibiotic policies targeting the pathogenic bacteria prevalent in their patient population . antibiotic discontinuation policies ( based on noninfectious causes for chest radiograph infiltrates and signs and symptoms suggesting that vap has resolved ) have been shown to reduce the antibiotic treatment duration without a significant deleterious effect on hospital mortality or recurrence of vap . a further curtailment of the multi - resistant bacteria may be possible with the rotation of antibiotics , particularly for gram - negative bacilli . over a seven - year period , antibiotic rotation for empirical and therapeutic use was associated with a reduction in the vap rate ( 23% before versus 16.3% following antibiotic rotation introduction ) and an increase in the susceptibility of gram - negative organisms to the antibiotics commonly used . fowler et al . treated 156 patients with suspected vap and showed that patients who received empiric therapy with anti - pseudomonal penicillins plus beta - lactamase inhibitors had lower in - hospital mortality than those who did not receive these antibiotics . retrospectively examined the microbiological sensitivities of 140 patients with vap and determined that sulbactam and cefoperazone were the most appropriate antibiotics . if staphylococcal pneumonia was suspected , a glycopeptide ( vancomycin or teicoplanin ) or combined trimethoprim - sulfamethoxazole was recommended , until the sensitivity results were obtained . therefore , a targeted approach with an appropriate dose of the right antibiotic guided by evidence , as has been suggested in the tarragona strategy , is one of the logical approaches for vap [ table 3 ] . several measures to prevent vap have proven to be effective and are generally recommended . the euro - nis study ( moro and jepsen ) has described different practices that may reduce exogenous infections due to better surveillance and better staff education.2)hand - washing and disinfection : these are the most important measures to prevent patient to patient spread of pathogens , as well as to protect healthcare workers from potential infections.3)change of the ventilator circuit not more than once per week : daily change of ventilator circuits was shown to be a risk factor for vap . although the optimal exchange interval has not been determined , a policy of circuit change once a week as compared to a 48-hour interval has been shown to be safe.4)orotracheal instead of nasotracheal intubation : nasotracheal intubation increases the risk for sinusitis and vap . therefore , orotracheal intubation should be the preferred technique.5)keeping the endotracheal tube cuff pressure optimized : the pressure of the endotracheal tube cuff should be optimized in order to prevent the leakage of colonized subglottic secretions into the lower airways.6)semi - recumbent body position : a reduction of aspiration into the lower airways , in a semi - recumbent versus a supine body position , has been shown by scinitgraphic means . moreover , the effect of a semi - recumbent position on the reduction of vap has been demonstrated.7)avoidance of paralytic medication : deeply sedated and relaxed patients clearly are at a higher risk of aspiration and vap . therefore , relaxation should be avoided whenever possible.8)avoidance of reintubation : reintubation was clearly demonstrated to represent a risk factor for vap . furthermore , it seems obvious that non - invasive ventilation instead of intubation should reduce the incidence of vap , particularly in patients who are immunocompromised.9)a meta - analysis examining 33 randomized sdd ( selective digestive decontamination ) trials involving 5,727 patients , demonstrated a significant reduction in the overall mortality ( 20% ) and in the incidence of respiratory tract infections ( 65% ) . a second systematic review in critically ill surgical patients showed an even greater benefit of sdd : mortality was reduced by 30% and the rates of pneumonia by 80% . sdd may be used in subsets of populations , such as , patients with trauma , pancreatitis , major burn injury , and those undergoing major elective surgery and transplantation . the euro - nis study ( moro and jepsen ) has described different practices that may reduce exogenous infections due to better surveillance and better staff education . hand - washing and disinfection : these are the most important measures to prevent patient to patient spread of pathogens , as well as to protect healthcare workers from potential infections . change of the ventilator circuit not more than once per week : daily change of ventilator circuits was shown to be a risk factor for vap . although the optimal exchange interval has not been determined , a policy of circuit change once a week as compared to a 48-hour interval has been shown to be safe . orotracheal instead of nasotracheal intubation : nasotracheal intubation increases the risk for sinusitis and vap . therefore , orotracheal intubation should be the preferred technique . keeping the endotracheal tube cuff pressure optimized : the pressure of the endotracheal tube cuff should be optimized in order to prevent the leakage of colonized subglottic secretions into the lower airways . semi - recumbent body position : a reduction of aspiration into the lower airways , in a semi - recumbent versus a supine body position , has been shown by scinitgraphic means . moreover , the effect of a semi - recumbent position on the reduction of vap has been demonstrated . avoidance of paralytic medication : deeply sedated and relaxed patients clearly are at a higher risk of aspiration and vap . avoidance of reintubation : reintubation was clearly demonstrated to represent a risk factor for vap . furthermore , it seems obvious that non - invasive ventilation instead of intubation should reduce the incidence of vap , particularly in patients who are immunocompromised . a meta - analysis examining 33 randomized sdd ( selective digestive decontamination ) trials involving 5,727 patients , demonstrated a significant reduction in the overall mortality ( 20% ) and in the incidence of respiratory tract infections ( 65% ) . a second systematic review in critically ill surgical patients showed an even greater benefit of sdd : mortality was reduced by 30% and the rates of pneumonia by 80% . sdd may be used in subsets of populations , such as , patients with trauma , pancreatitis , major burn injury , and those undergoing major elective surgery and transplantation . the department of health in the uk published the following  high impact interventions for ventilated patients in june 2007 . a)elevation of the head of bed to 35 - 40 degreesb)sedation holdingc)deep vein thrombosis prophylaxisd)gastric ulcer prophylaxise)appropriate humidification of inspired gasf)appropriate tubing managementg)suctioning of respiratory secretions ( including use of gloves and decontaminating hands before and after the procedure)h)routine oral hygiene as per local policy 
  elevation of the head of bed to 35 - 40 degrees deep vein thrombosis prophylaxis gastric ulcer prophylaxis appropriate humidification of inspired gas appropriate tubing management suctioning of respiratory secretions ( including use of gloves and decontaminating hands before and after the procedure ) routine oral hygiene as per local policy of all these interventions , elevation of the head , gastric ulcer prophylaxis , continuous suctioning of the subglottic secretions , chlorhexidine mouthwash , enteral feeding with a post - pyloric feeding tube , and daily sedation interruption are of particular importance to prevent vap . the nascent randomized trial explored the possibility of using a silver - coated endotracheal tube and found a statistically significant reduction in the incidence of vap and delayed time to vap when compared to a similar uncoated tube . although cost - effectiveness was a presumed hindrance , a more recent study has found that the silver - coated endotracheal tubes yielded persistent savings per case of vap prevented . many controversies still remain with regard to the epidemiology , diagnosis , prognosis , and therapy of ventilator - associated pneumonia . in particular , the proportion of ventilator - associated pneumonia that can be prevented by improving the quality of care is yet to be fully understood . to address these issues , a thorough understanding of the precise natural history of ventilator - associated pneumonia at a cellular level , and establishing the sequence of events between colonization and infection , is needed . till such time , vap will continue to present as a major therapeutic challenge to clinicians , particularly when patient management is complicated by the presence of underlying conditions .
ventilator - associated pneumonia ( vap ) is the most common infection in mechanically ventilated patients , and carries the highest mortality . 
 an early diagnosis and definitive management not only reduces the overall mortality , but also brings down the burden of health care to the patient by reducing the cost , length of intensive care unit ( icu ) stay , duration of mechanical ventilation , and so on . out of the various scoring systems , the clinical pulmonary infection score ( cpis ) calculation for vap has a good sensitivity ( 72% ) and specificity ( 85% ) and the targeted antibiotic therapy in the appropriate dosage is found to be more beneficial than empirical treatment . 
 although controversies persist on several issues , preventive strategies like head elevation by 30 degrees , cuff pressure monitoring , avoidance of sedatives and muscle relaxants , and so on , have been found to reduce the occurrence of vap .