in this issue of critical care , nseir and coworkers   provide interesting data from a randomized trial of antibiotic therapy for ventilator - associated tracheobronchitis ( vat ) . although ventilator - associated pneumonia ( vap ) has been the major focus of critical care providers , perhaps our focus should also include vat , which may be a precursor to vap or overlap with early vap [ 1 - 5 ] . understanding vat may have important implications for the early diagnosis , therapy , and prevention of vap . in comparison with vap , vat is plagued by little clinical data and several questions : how do we define it ? what level of bacteria in endotracheal aspirates is diagnostic ? when is antibiotic therapy indicated and for how long ? most bacteria enter the lower respiratory tract by leakage of bacteria and oropharyngeal secretions around the endotracheal tube cuff , resulting in colonization , vat , or vap . furthermore , the primary exit route for bacteria out of the lower respiratory tract is impeded by the endotracheal tube , patient sedation , and a reliance on mechanical suctioning rather than spontaneous coughing . the lower respiratory tract in the ventilated patient is a continuous ' battleground ' between the numbers , types , and virulence of the incoming bacteria versus the lung 's incredible mechanical , cellular , and humoral defenses . the outcome for each patient is either lower airway colonization or shades of grey from vat to vap . diagnoses of both vat and vap rely on clinical and systemic signs of infection ( fever , leukocytosis , reduced oxygenation ) plus purulent sputum with high concentrations of bacteria (  10colony - forming units [ cfu]/ml ) in the endotracheal aspirate . diagnoses of vap rely on distal samples of bacteria obtained from bronchoscopic and non - bronchoalveolar lavage (  10cfu / ml )   or protected specimen brush ( psb ) (  10cfu / ml ) . definitions of vat and vap have been based on different sampling techniques and microbiologic thresholds , which may make discrimination between vat and vap difficult . although vap requires evidence of a new and persistent infiltrate on a chest x - ray , the sensitivity and specificity of x - rays are variable and , though improved with computerized tomographic scans , still have limitations , especially in patients with severe congestive heart failure or adult respiratory distress syndrome . for vap , and probably vat , nseir and coworkers   reported an observational cohort of medical and surgical intensive care unit ( icu ) patients who had a 10.6% incidence of vat . vat was associated with an increased length of stay ( los ) in the icu and more mechanical ventilator days , but those receiving antimicrobial therapy had a trend toward decreased los , fewer mechanical ventilator days , and lower mortality . in a more recent case control study in ventilated patients with chronic respiratory failure , patients with vat had a significantly longer duration of mechanical ventilation ( 17 versus 8 days ; p < 0.001 ) and icu stays ( 24 versus 12 days ; p < 0.001 ) . nouria and coworkers   compared the impact of ofloxacin versus placebo in a randomized trial of mechanically ventilated patients with chronic lung disease and noted significantly better outcomes in the ofloxacin group . a'court and coworkers   studied the natural history of colonization in mechanically ventilated patients using serial non - bronchoscopic bronchial lavage with quantitative cultures collected every 48 hours . these investigators reported a significant increase in lower respiratory tract colony counts which started 2 days before the clinical onset of vap , which may have represented either vat or early vap not detected by chest x - ray . in this issue , nseir and coworkers   present interesting data from a small randomized , controlled , multicenter trial of patients with vat who were randomly assigned to antibiotic therapy versus no therapy . vat was defined as a first episode of fever of greater than 38c , purulent sputum production , endotracheal aspirate having greater than or equal to 10cfu / ml of a new pathogen , but no radiographic signs of vap on a chest x - ray . pseudomonas aeruginosa , acinetobacter baumannii , and methicilllin - resistant staphylococcus aureus ( mrsa ) were the most common pathogens isolated . results were presented as intention - to - treat ( itt ) and a modified itt ( mitt ) analysis which excluded patients with potential confounders . in both analyses , the antibiotic - treated group had a significant decrease in vap ( p < 0.01 ) , more mechanical ventilation - free days ( p < 0.001 ) , and a lower icu mortality ( p < 0.05 ) . these data of nseir and coworkers   are interesting and provocative and suggest that vat caused by these pathogens may be a marker for patients at high risk for developing vap and that early appropriate antibiotic therapy for vat or preemptive therapy for early vap may significantly improve patient outcomes . study limitations of note include the following : lack of blinding ; low numbers of patients ; the study was stopped before randomization blocks were attained ; an independent blinded committee did not evaluate the endpoints ; and , finally , computer - assisted tomography was not performed systematically to exclude vap . the data of nseir and coworkers   need confirmation but suggest a new paradigm to assess tracheal colonization , whether treating vat or early vap . also , treatment of vat may reduce lung inflammation , which may translate into earlier extubation and reduced risk for vap . finally , the presence of high concentrations of a bacterial pathogen in the endotracheal aspirate may be an important clinical clue that antibiotic therapy is needed to aid failing host defenses and reduce patient mortality , morbidity , and health care costs . the limitations of the study by nseir and coworkers   underscore the need for larger collaborative national and international networks to develop well - designed trials , with independent data analysis and data safety monitoring boards , that would greatly increase our understanding of disease pathogenesis , prevention , and treatment . such a network could provide a foundation on which to build vitally needed ' gold standards ' to improve patient care , outcomes , and prevention of vap and other health care - associated infections . progress usually is based on a series of small steps , but bigger and better steps are not only possible , but vitally needed . cfu = colony - forming units ; icu = intensive care unit ; itt = intention - to - treat ; los = length of stay ; psb = protected specimen brush ; vap = ventilator - associated pneumonia ; vat = ventilator - associated tracheobronchitis .
nosocomial lower respiratory tract infections are a common cause of morbidity and mortality in intensive care unit ( icu ) patients . 
 although many studies have investigated the management and prevention of ventilator - associated pneumonia ( vap ) , few have focused on ventilator - associated tracheobronchitis ( vat ) . in this issue of critical care , nseir and 
 coworkers present interesting data from a randomized controlled study of antimicrobial therapy for vat . 
 patients randomly assigned to antibiotic therapy had more mechanical ventilation - free days ( p < 0.001 ) , fewer episodes of vap ( 13% versus 47% ; p < 0.001 ) , and a lower icu mortality rate ( 18% versus 47% ; p = 0.05 ) than those without antibiotic therapy . 
 although this study has limitations , the data suggest that vat may be an important risk factor for vap or overlap with early vap . 
 more importantly , targeted antibiotic therapy for vat may improve patient outcomes and become a new paradigm for prevention or early therapy for vap .