***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Patients with severe burns are at increased risk of developing methicillin-resistant Staphylococcus aureus ( MRSA ) ventilator-associated pneumonia . This study was design ed to determine whether MRSA pneumonia can be prevented by prophylactic administration of trimethoprim-sulfamethoxazole ( TMP-SMX ) . METHODS We conducted a prospect i ve , r and omized , placebo-controlled study in patients with severe burns ( > or = 20 % ) , who required ventilator support . Prophylaxis was done with oral TMP-SMX ( 80 mg/400 mg ) three times daily for 10 days from 4 to 6 days after burn injury . The incidence of MRSA pneumonia and the side effects were evaluated during the administration period . RESULTS Twenty-one patients were assigned to receive TMP-SMX , and 19 patients to receive placebo .  The incidence of MRSA pneumonia was 4.8 % in the TMP-SMX group and 36.8 % in the placebo group , showing a significant difference ( p = 0.017 ) . No major side effects of therapy were seen in the TMP-SMX group . CONCLUSION Prophylactic treatment with TMP-SMX can prevent MRSA pneumonia in severely burned patients Objective : To determine whether use of a single heat and moisture exchanger ( HME ) for ≤120 hrs affects efficiency , resistance , level of bacterial colonization , frequency rate of nosocomial pneumonia , and cost compared with changing the HME every 24 hrs . Design : Prospect i ve , controlled , r and omized , unblinded study . Setting : Surgical intensive care unit at a university teaching hospital . Patients : A total of 220 consecutive patients requiring mechanical ventilation for > 48 hrs . Interventions : Patients were r and omized to one of three groups : a ) hygroscopic HME ( Aqua+ ) changed every 24 hrs ( HHME‐24 ) ; b ) hydrophobic HME ( Duration HME ) changed every 120 hrs ( HME‐120 ) ; and c ) hygroscopic HME ( Aqua+ ) changed every 120 hrs ( HHME‐120 ) . Devices in all groups could be changed at the discretion of the staff when signs of occlusion or increased resistance were identified . Measurements and Main Results : Daily measurements of inspired gas temperature , inspired relative humidity , and device resistance were made . Additionally , daily cultures of the patient side of the device were accomplished . The frequency rate of nosocomial pneumonia was made by using clinical criteria . Ventilatory support variables , airway care , device costs , and clinical indicators of humidification efficiency ( sputum volume , sputum efficiency ) were also recorded . Prolonged use of both hygroscopic and hydrophobic devices did not diminish efficiency or increase resistance . There was no difference in the number of colony‐forming units from device cultures over the 5‐day period and no difference between colony‐forming units in devices changed every 24 hrs compared with devices changed after 120 hrs . The average duration of use was 23 ± 4 hrs in the HHME‐24 group , 73 ± 13 hrs in the HME‐120 group , and 74 ± 9 hrs in the HHME‐120 group . Mean absolute humidity was greater for the hygroscopic devices ( 30.4 ± 1.1 mg of H2O/L ) compared with the hydrophobic devices ( 27.8 ± 1.3 mg of H2O/L ) . The frequency rate of nosocomial pneumonia was 8 % ( 8:100 ) in the HHME‐24 group , 8.3 % ( 5:60 ) in the HME‐120 group , and 6.6 % ( 4:60 ) in the HHME‐120 group . Pneumonia rates per 1000 ventilatory support days were 20:1000 in the HHME‐24 group , 20.8:1000 in the HME‐120 group , and 16.6:1000 in the HHME‐120 group . Costs per day were $ 3.24 for the HHME‐24 group , $ 2.98 for the HME‐120 group , and $ 1.65 for the HHME‐120 group . Conclusions : Changing the hydrophobic or hygroscopic HME after 3 days does not diminish efficiency , increase resistance , or alter bacterial colonization . The frequency rate of nosocomial pneumonia was also unchanged . Use of HMEs for > 24 hrs , up to 72 hrs , is safe and cost effective Nosocomial pneumonia is the leading cause of death among all hospital-acquired infections [ 1 ] . The estimated incidence of nosocomial pneumonia in intensive care units ranges from 10 % to 65 % ; most studies [ 2 - 6 ] show case fatality rates of more than 20 % . Ventilator-associated pneumonia specifically refers to nosocomial pneumonia that develops in a mechanically ventilated patient and that was not present at the time of airway intubation [ 7 ] . Various clinical risk factors have been associated with an increased incidence of ventilator-associated pneumonia , either because they predispose the patient to bacterial colonization of the oropharynx and stomach ( for example , the administration of antacids or histamine-2-receptor antagonists ) or because they facilitate aspiration of contaminated contents from these sites ( for example , supine positioning ) [ 1 , 2 , 8 , 9 ] . Craven and colleagues [ 10 ] first showed that the frequency of ventilator circuit changes also influences the incidence of ventilator-associated pneumonia . They found that changing circuits every 24 rather than every 48 hours was independently associated with the occurrence of nosocomial pneumonia [ 10 ] . This association has been attributed to increased manipulation of the patient , the endotracheal tube , and the ventilator circuit , which results in increased aspiration of contaminated tubing condensate or upper airway secretions [ 10 , 11 ] . More recently , several groups of investigators have found that ventilator circuits can be used safely for more than 48 hours without increasing the incidence of nosocomial pneumonia [ 12 - 16 ] . However , because of limitations in the design of these studies and the small number of patients prospect ively examined , the Centers for Disease Control and Prevention has given no clear recommendation for the maximum length of time that ventilator circuits can safely be left in place during prolonged mechanical ventilation [ 17 ] . This has result ed in the development of ambiguous guidelines about the frequency with which ventilator circuits should be changed [ 18 , 19 ] and in a call for well- design ed investigations to resolve this issue [ 20 ] . We did a r and omized , controlled trial to compare the effect and cost-efficacy of routine and no routine ventilator circuit changes in patients having prolonged mechanical ventilation . Our main goals were to determine 1 ) the incidence and outcome of ventilator-associated pneumonia in patients receiving scheduled ventilator circuit changes and 2 ) whether this incidence was increased in patients whose ventilator circuits remained unchanged . Methods Study Location and Patients The study was conducted at two university-affiliated teaching hospitals : Barnes Hospital ( 900 beds ) and Jewish Hospital ( 450 beds ) . During a 7-month period ( June 1994 to December 1994 ) , all patients receiving mechanical ventilation in the intensive care units of these hospitals ( surgical , trauma , medical , cardiothoracic , and neurosurgical units at Barnes Hospital ; surgical , medical , and cardiothoracic units at Jewish Hospital ) were potentially eligible for this investigation . Patients were entered into the trial if they were older than 18 years and had received mechanical ventilation for more than 5 days .  Mechanical ventilation for more than 5 days was predetermined , on the basis of our previous experience at these institutions [ 2 , 21 ] , to be necessary so that a more homogeneous cohort of patients requiring prolonged mechanical ventilation could be accrued . Patients were excluded if they were likely to be extubated within 24 hours of r and omization , if they had transferred from other hospitals and had already received mechanical ventilation for more than 24 hours , if they had had lung transplantation , or if they had active hemoptysis . Barnes Hospital and Jewish Hospital share the same respiratory therapy and infection control departments . The study was approved by the Washington University School of Medicine Human Studies Committee and the Institutional Review Board of Jewish Hospital . Both waived the requirement for informed consent because this study was a quality assessment of two low-risk practice s already in clinical use . Study Design Patients were r and omly assigned to receive no routine ventilator circuit changes or circuit changes every 7 days within 24 hours of meeting eligibility criteria . A schedule of changing ventilator circuits every 7 days was selected on the basis of available clinical data [ 12 - 16 ] and our survey of 16 regional medical centers ( DM Baker . Unpublished communication ) . Stratification according to hospital site was done before r and omization to control for differences in patient population s and health care personnel . R and omization within each hospital was done using opaque , sealed envelopes , which were opened at the time each patient was enrolled in the study . For the purpose s of this investigation , ventilator circuits were defined to include gas delivery tubing , humidifier water reservoirs , water traps , and medication delivery devices ( such as metered-dose inhaler chambers or adapters ) . Ventilator circuits could be changed at any time , at the discretion of individual care providers ( physicians , nurses , and respiratory therapists ) , secondary to a mechanical failure of the ventilator circuit ( such as an air leak ) or visible soil ( such as that result ing from hemoptysis or aspirated emesis ) . Scheduled ventilator circuit changes were done during the evening or night shifts to minimize the identification of individual patient group assignments to blinded investigators . All nonscheduled circuit changes were done when an appropriate indication for the circuit change ( that is , a mechanical defect or soil ) was identified . Patients transferred to the operating room for a surgical procedure ( such as tracheotomy ) or to diagnostic radiology received the same mechanical ventilator and circuit when they returned to the intensive care unit . The ventilators used for this study included Siemens Servo 900C ( Siemens-Elema Ventilator Systems , Schaumburg , Illinois ) , Puritan-Bennett 700 Series ( Puritan-Bennett Corporation , Carlsbad , California ) , and Bird 8400 Series ventilators ( Bird Products Corporation , Palm Springs , California ) . All ventilators were equipped with wick-type humidifiers ( Concha Therm III Plus , Hudson Respiratory Care , Inc. , Temecula , California ) filled with sterile irrigation water . All ventilator circuits were disposable ( Hudson Respiratory Care , Inc. , model 1613 ) and equipped with Y connectors . Each ventilator circuit had an attached trap for the collection of tubing condensate ( Marquest Medical Products , Inc. , Englewood , Colorado ) . As per our st and ard procedure , all ventilator circuits were monitored at least every 2 hours and water traps were emptied when full . Data Collection For all study patients , the following characteristics were prospect ively recorded by one of the investigators : age , sex , diagnosis at hospital admission , indication for mechanical ventilation , Premorbid Lifestyle score , the ratio of arterial blood oxygen tension to the concentration of inspired oxygen ( Pao 2 : Fio 2 ) , severity of illness based on APACHE II ( Acute Physiology and Chronic Health Evaluation [ 22 ] ) scores , the Organ System Failure Index , and the occurrence of a witnessed aspiration event . Specific processes of medical care examined to assess risk factors for ventilator-associated pneumonia were the administration of antacids or histamine-2-receptor antagonists , pharmacologic aerosol treatments during mechanical ventilation ( such as bronchodilators , antibiotics , and mucolytics ) , fiberoptic bronchoscopy , surgical tracheostomy  , and the number of ventilator circuit changes  done and the indications for those changes ( scheduled according to the study protocol , soil , or mechanical defect ) . Two of the investigators made daily rounds in the intensive care units of each hospital to identify eligible patients . Patients entered into the study were prospect ively followed for the occurrence of ventilator-associated pneumonia until they were successfully weaned from mechanical ventilation , were discharged from the hospital , or died . All patients suspected by these investigators of having ventilator-associated pneumonia were prospect ively and independently review ed by another investigator who was blinded to the patient 's treatment group assignment . The diagnosis of ventilator-associated pneumonia was strictly based on the predetermined criteria described below . Patients could not be entered into the study more than once during the same hospitalization , and only the first episode of ventilator-associated pneumonia was evaluated . In addition to the occurrence of ventilator-associated pneumonia , secondary outcomes assessed included the length of hospitalization , the duration of mechanical ventilation , hospital mortality , and mortality directly attributed to ventilator-associated pneumonia . All study variables were recorded in data collection books maintained at each of the participating hospitals . Definitions All definitions were selected prospect ively as part of the original study design . The Premorbid Lifestyle score was used as previously defined [ 23 ] : Zero indicated that the patient was employed without restriction ; 1 indicated that the patient was independent , fully ambulatory , not employed , or employed with restriction ; 2 indicated that the patient had restricted activities , could live alone and get out of the house to do basic necessities , or had severely limited exercise ability ; 3 indicated that the patient was housebound , could not get out of the house unassisted , could not live alone , or could not do heavy chores ; and 4 indicated that 
    Output:
    
Such criteria result in good sensitivity but poor specificity .
Semi-Recumbent Patient Positioning Background and Practice Description Positioning of critically ill patients may affect the incidence of ventilator-associated pneumonia .
Supine patient positioning has been shown to be independently associated with the development of ventilator-associated pneumonia , possibly because of an increased risk for gastroesophageal reflux and aspiration ( 13 ) .
Semi-recumbent positioning ( defined as elevation of the head of the bed to 45 degrees ) may decrease the risk for ventilator-associated pneumonia .
Medications that alter the gastric pH , such as H2-antagonists and antacids , may increase organism counts and increase the risk for ventilator-associated pneumonia ( 18 ) .
Sucralfate , an alternative prophylactic agent that does not affect gastric pH , may not increase this risk .
Conclusions and Recommendations Stress ulcer prophylaxis with any agent may increase the risk for ventilator-associated pneumonia ( 18 ) .
Therefore , sucralfate may decrease risk when compared with H2-antagonists but not when compared with placebo .
The data comparing stress ulcer prophylaxis with sucralfate and H2-antagonists suggest a decreased