human
***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: These experiments tested the hypothesis that a relatively short duration of controlled mechanical ventilation ( MV ) will impair diaphragmatic maximal specific force generation ( specific P(o ) ) and that this force deficit will be exacerbated with increased time on the ventilator . To test this postulate , adult Sprague-Dawley rats were r and omly divided into one of six experimental groups : 1 ) control  ( n = 12 ) ; 2 ) 12 h of MV ( n = 4 ) ; 3 ) 18 h of MV ( n = 4 ) ; 4 ) 18 h of anesthesia and spontaneous breathing ( n = 4 ) ; 5 ) 24 h of MV ( n = 7 ) ; and 6 ) 24 h of anesthesia and spontaneous breathing ( n = 4 ) . MV animals were anesthetized , tracheostomized , and ventilated with room air . Animals in the control group were acutely anesthetized but were not exposed to MV . Animals in two spontaneous breathing groups were anesthetized and breathed spontaneously for either 18 or 24 h. No differences ( P > 0.05 ) existed in diaphragmatic specific P(o ) between control and the two spontaneous breathing groups . In contrast , compared with control , all duration s of MV result ed in a reduction ( P < 0.05 ) in diaphragmatic specific tension at stimulation frequencies ranging from 15 to 160 Hz . Furthermore , the MV-induced decrease in diaphragmatic specific P(o ) was time dependent , with specific P(o ) being approximately 18 and approximately 46 % lower ( P < 0.05 ) in animals mechanically ventilated for 12 and 24 h , respectively . These data support the hypothesis that relatively short-term MV impairs diaphragmatic contractile function and that the magnitude of MV-induced force deficit increases with time on the ventilator AIM To compare T-tube and pressure support ventilation ( PSV ) as two methods of weaning patients from mechanical ventilation . METHODS A r and omized prospect i ve study included 260 patients who received mechanical ventilation for more than 48 h , and who were admitted to the intensive care unit ( ICU ) at Dr. Josip Bencevic General Hospital in Slavonski Brod , between August 1999 and October 2000 . After fulfilling the clinical criteria for weaning , the patients were r and omly assigned to a 2-h trial of spontaneous breathing either with a T-tube system ( n=110 ) or PSV of 8 cm H2O ( n=150 ) . The patients who fulfilled weaning criteria at the end of the 2-h trial were extubated . If any signs of poor procedure tolerance were observed during the 2-h trial , the mechanical ventilation was reinstituted . In such patients , the same weaning procedure was repeated after 24 h , or when the patient 's clinical condition permitted . Two methods of weaning were compared according to the patient 's clinical characteristics , objective parameters , and procedure outcome . RESULTS Eighty ( 73 % ) patients in the T-tube group and 120 ( 80 % ) patients in PSV group successfully completed the 2-h trial and were extubated . Thirty patients in the T-tube group and 30 in the PSV group had weaning difficulties . Total length of additional mechanical ventilation and total length of stay at ICU were significantly shorter in patients undergoing PSV weaning ( p<0.001 for all , Man-Whitney test ) . For the patients with weaning difficulties and Acute Physiology and Chronic Health Evaluation ( APACHE ) II score > 20 on admission , PSV was the superior method of weaning according to rate of successful extubation , time of weaning from mechanical ventilation , total time of mechanical ventilation , and length of ICU stay ( p<0.001 for all , Man-Whitney test ) . CONCLUSION In patients with weaning difficulties , PSV with 8 cm H(2)O was more successful weaning method than T-tube A 2-h T-tube trial of spontaneous breathing was used in selecting patients ready for extubation and discontinuation of mechanical ventilation . However , some doubt remains as to whether it is the most appropriate method of performing a spontaneous breathing trial . We carried out a prospect i ve , r and omized , multicenter study involving patients who had received mechanical ventilation for more than 48 h and who were considered by their physicians to be ready for weaning according to clinical criteria and st and ard weaning parameters . Patients were r and omly assigned to undergo a 2-h trial of spontaneous breathing in one of two ways : with a T-tube system or with pressure support ventilation of 7 cm H2O . If a patient had signs of poor tolerance at any time during the trial , mechanical ventilation was reinstituted . Patients without these features at the end of the trial were extubated . Of the 246 patients assigned to the T-tube group , 192 successfully completed the trial and were extubated ; 36 of them required reintubation . Of the 238 patients in the group receiving pressure support ventilation  , 205 were extubated and 38 of them required reintubation . The percentage of patients who remained extubated after 48 h was not different between the two groups ( 63 % T-tube , 70 % pressure support ventilation , p = 0.14 ) . The percentage of patients falling the trial was significantly higher when the T-tube was used ( 22 versus 14 % , p = 0.03 ) . Clinical evolution during the trial was not different in patients reintubated and successfully extubated . ICU mortality among reintubated patients was significantly higher than in successfully extubated patients ( 27 versus 2.6 % , p < 0.001 ) . Spontaneous breathing trials with pressure support or T-tube are suitable methods for successful discontinuation of ventilator support in patients without problems to resume spontaneous breathing OBJECTIVE : To evaluate the clinical relevance of the weaning from mechanical ventilation classification system derived from the 2005 international consensus conference , in patients who receive mechanical ventilation for more than 48 hours , and evaluate its correlation with prognosis . METHODS : We conducted a retrospective cohort study in a 12-bed intensive care unit ( ICU ) in a teaching hospital . We included patients who required > 48 hours of mechanical ventilation and who passed a spontaneous breathing trial ( SBT ) .  Weaning and sedation  were monitored according to st and ardized protocol -directed procedures . We collected data on physiological characteristics , mechanical ventilation duration , ICU and hospital stay , and mortality from the medical records data base . We assessed one-year mortality with a prospect i ve , st and ardized method . Multivariate logistic regression was performed to evaluate the association between weaning categories and outcome . RESULTS : We included 329 ventilation episodes , in which 115 patients passed at least one SBT . Thirty-four patients ( 30 % ) succeeded in their first SBT ( simple weaning group ) , 47 patients ( 40 % ) succeeded in their 2nd or 3rd SBT or in less than 7 days of weaning ( the difficult weaning group ) , and 34 patients ( 30 % ) required more than 3 SBTs or more than 7 days of weaning ( the prolonged weaning group ) . There were significant differences in ICU and hospital mortality between the simple , difficult , and prolonged-weaning groups . Prolonged weaning was an independent risk factor for longer ICU stay ( odds ratio 15.11 , 95 % CI 1.61–141.91 , P = .01 ) and hospital mortality ( odds ratio 3.66 , 95 % CI 0.99–13.51 ) . However , the weaning process did not impact one-year mortality ( odds ratio 2.61 , 95 % CI 0.82–8.35 ) . CONCLUSIONS : The new weaning classification system is clinical ly relevant and correlates to ICU and hospital mortality , but not to one-year mortality Because the clinics in a multiclinic r and omized clinical trial represent neither fixed stratification effects nor r and om classificatory effects , the appropriate analysis of data from such a trial has been the subject of controversy and debate . The following are some of the elements of controversy that are discussed and for which some bases for resolution are proposed . Is it ever valid to ignore the effects of clinics in the analysis ? Is it ever valid to drop clinics from the analysis ? Is a multiclinic clinical trial similar in structure or not to a single-clinic clinical trial in which patients have been stratified on a classificatory factor ? Assuming that clinics will be taken account of in the analysis , should it be the weighted or the unweighted average of within-clinic treatment differences that is to be taken as the best estimate of the overall difference between the treatments ? How should the data be analyzed if there is evidence of treatment-by-clinic interaction Weaning from mechanical ventilation was categorised as simple , difficult or prolonged by an international task force of the American Thoracic Society/European Respiratory Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine/Sociéte de Réanimation de Langue Française in 2007 . This new classification has not been tested in clinical practice . The objective of the present study was to determine the incidence and outcome of weaning according to the new categories . We included medical and surgical patients who required mechanical ventilation in a prospect i ve , multicentre , 6-month cohort study . From an initial cohort of 510 patients , 257 intubated patients started weaning .  Of these patients , the cumulative incidences of simple , difficult , and prolonged weaning were 152 ( 59 % ) , 68 ( 26 % ) and 37 ( 14 % ) , respectively . Hospital mortality was increased in patients with prolonged ( 32 % ) but not difficult ( 9 % ) weaning in comparison with those with simple weaning ( 13 % ) , overall p = 0.0205 . In a multivariate logistic regression model , prolonged but not difficult weaning was associated with an increased risk of death . Ventilator-free days and intensive care unit (ICU)-free days were decreased in both difficult and prolonged weaning . In conclusion , the new weaning category prolonged weaning is associated with increased mortality and morbidity in the ICU . The new category difficult to wean was associated with increased morbidity , but not mortality INTRODUCTION : Echocardiographic , electrocardiographic and other cardiorespiratory variables can change during weaning from mechanical ventilation . OBJECTIVES : To analyze changes in cardiac function , using Doppler echocardiogram , in critical patients during weaning from mechanical ventilation  , using two different weaning methods : pressure support ventilation and T‐tube ; and comparing patient subgroups : success vs. failure in weaning . METHODS : R and omized crossover clinical trial including patients under mechanical ventilation for more than 48 h and considered ready for weaning . Cardiorespiratory variables , oxygenation , electrocardiogram and Doppler echocardiogram findings were analyzed at baseline and after 30 min in pressure support ventilation and T‐tube . Pressure support ventilation vs. T‐tube and weaning success vs. failure were compared using ANOVA and Student 's t‐test . The level of significance was p<0.05 . RESULTS : Twenty‐four adult patients were evaluated . Seven patients failed at the first weaning attempt . No echocardiographic or electrocardiographic differences were observed between pressure support ventilation and T‐tube . Weaning failure patients presented increases in left atrium , intraventricular septum thickness , posterior wall thickness and diameter of left ventricle and shorter isovolumetric relaxation time . Successfully weaned patients had higher levels of oxygenation . CONCLUSION : No differences were observed between Doppler echocardiographic variables and electrocardiographic and other cardiorespiratory variables  during pressure support ventilation and T‐tube .  However cardiac structures were smaller , isovolumetric relaxation time was larger , and oxygenation level was greater in successfully weaned patients PURPOSE The purpose of this article was to investigate the effect of an additional 1-hour T-piece trial at the level of minimum pressure support ( PSmin ) on weaning outcome . MATERIAL S AND METHODS Open , r and omized , prospect i ve study of 44 patients who had received mechanical ventilation for more than 3 days . Thirty-six patients satisfied the protocol . There were 42 weaning trials . The patients were r and omized into an intervention group ( additional 1-hour period of T-piece trial ) and a control group ( extubation directly ) at PSmin . Blood gas analysis and estimation of respiratory and hemodynamic variables  were performed at the 15 cm H2O level of pressure support . Measurements were repeated at PSmin and during weaning process ( in intervention group ) . RESULTS Mean PSmin level was 7.6 ( + /- 1.9 ) cm H2O . There were no differences in total ventilation time ( TVT ) , acute physiology and chronic health evaluation ( APACHE ) II score , nutritional indices , and respiratory mechanics on PSmin between the two groups . The weaning success rate and the reintubation rate were similar for the intervention group ( 55 % and 18 % , respectively ) and control group ( 70 % and 20 % , respectively ) . Work of breathing , pressure time product , and tidal volume significantly worsened after a 1-hour T-piece trial when compared with those values measured at PSmin in the intervention group ( P < .05 ) . For the combined patient sample , TVT and tidal volume at PSmin were significantly different between the patients with weaning success ( 246 + /- 195 hours , 0.43 + /- 0.11 L ) and those with weaning failure ( 407 + 
    Output:
    
agent
***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: These experiments tested the hypothesis that a relatively short duration of controlled mechanical ventilation ( MV ) will impair diaphragmatic maximal specific force generation ( specific P(o ) ) and that this force deficit will be exacerbated with increased time on the ventilator . To test this postulate , adult Sprague-Dawley rats were r and omly divided into one of six experimental groups : 1 ) control  ( n = 12 ) ; 2 ) 12 h of MV ( n = 4 ) ; 3 ) 18 h of MV ( n = 4 ) ; 4 ) 18 h of anesthesia and spontaneous breathing ( n = 4 ) ; 5 ) 24 h of MV ( n = 7 ) ; and 6 ) 24 h of anesthesia and spontaneous breathing ( n = 4 ) . MV animals were anesthetized , tracheostomized , and ventilated with room air . Animals in the control group were acutely anesthetized but were not exposed to MV . Animals in two spontaneous breathing groups were anesthetized and breathed spontaneously for either 18 or 24 h. No differences ( P > 0.05 ) existed in diaphragmatic specific P(o ) between control and the two spontaneous breathing groups . In contrast , compared with control , all duration s of MV result ed in a reduction ( P < 0.05 ) in diaphragmatic specific tension at stimulation frequencies ranging from 15 to 160 Hz . Furthermore , the MV-induced decrease in diaphragmatic specific P(o ) was time dependent , with specific P(o ) being approximately 18 and approximately 46 % lower ( P < 0.05 ) in animals mechanically ventilated for 12 and 24 h , respectively . These data support the hypothesis that relatively short-term MV impairs diaphragmatic contractile function and that the magnitude of MV-induced force deficit increases with time on the ventilator AIM To compare T-tube and pressure support ventilation ( PSV ) as two methods of weaning patients from mechanical ventilation . METHODS A r and omized prospect i ve study included 260 patients who received mechanical ventilation for more than 48 h , and who were admitted to the intensive care unit ( ICU ) at Dr. Josip Bencevic General Hospital in Slavonski Brod , between August 1999 and October 2000 . After fulfilling the clinical criteria for weaning , the patients were r and omly assigned to a 2-h trial of spontaneous breathing either with a T-tube system ( n=110 ) or PSV of 8 cm H2O ( n=150 ) . The patients who fulfilled weaning criteria at the end of the 2-h trial were extubated . If any signs of poor procedure tolerance were observed during the 2-h trial , the mechanical ventilation was reinstituted . In such patients , the same weaning procedure was repeated after 24 h , or when the patient 's clinical condition permitted . Two methods of weaning were compared according to the patient 's clinical characteristics , objective parameters , and procedure outcome . RESULTS Eighty ( 73 % ) patients in the T-tube group and 120 ( 80 % ) patients in PSV group successfully completed the 2-h trial and were extubated . Thirty patients in the T-tube group and 30 in the PSV group had weaning difficulties . Total length of additional mechanical ventilation and total length of stay at ICU were significantly shorter in patients undergoing PSV weaning ( p<0.001 for all , Man-Whitney test ) . For the patients with weaning difficulties and Acute Physiology and Chronic Health Evaluation ( APACHE ) II score > 20 on admission , PSV was the superior method of weaning according to rate of successful extubation , time of weaning from mechanical ventilation , total time of mechanical ventilation , and length of ICU stay ( p<0.001 for all , Man-Whitney test ) . CONCLUSION In patients with weaning difficulties , PSV with 8 cm H(2)O was more successful weaning method than T-tube A 2-h T-tube trial of spontaneous breathing was used in selecting patients ready for extubation and discontinuation of mechanical ventilation . However , some doubt remains as to whether it is the most appropriate method of performing a spontaneous breathing trial . We carried out a prospect i ve , r and omized , multicenter study involving patients who had received mechanical ventilation for more than 48 h and who were considered by their physicians to be ready for weaning according to clinical criteria and st and ard weaning parameters . Patients were r and omly assigned to undergo a 2-h trial of spontaneous breathing in one of two ways : with a T-tube system or with pressure support ventilation of 7 cm H2O . If a patient had signs of poor tolerance at any time during the trial , mechanical ventilation was reinstituted . Patients without these features at the end of the trial were extubated . Of the 246 patients assigned to the T-tube group , 192 successfully completed the trial and were extubated ; 36 of them required reintubation . Of the 238 patients in the group receiving pressure support ventilation  , 205 were extubated and 38 of them required reintubation . The percentage of patients who remained extubated after 48 h was not different between the two groups ( 63 % T-tube , 70 % pressure support ventilation , p = 0.14 ) . The percentage of patients falling the trial was significantly higher when the T-tube was used ( 22 versus 14 % , p = 0.03 ) . Clinical evolution during the trial was not different in patients reintubated and successfully extubated . ICU mortality among reintubated patients was significantly higher than in successfully extubated patients ( 27 versus 2.6 % , p < 0.001 ) . Spontaneous breathing trials with pressure support or T-tube are suitable methods for successful discontinuation of ventilator support in patients without problems to resume spontaneous breathing OBJECTIVE : To evaluate the clinical relevance of the weaning from mechanical ventilation classification system derived from the 2005 international consensus conference , in patients who receive mechanical ventilation for more than 48 hours , and evaluate its correlation with prognosis . METHODS : We conducted a retrospective cohort study in a 12-bed intensive care unit ( ICU ) in a teaching hospital . We included patients who required > 48 hours of mechanical ventilation and who passed a spontaneous breathing trial ( SBT ) .  Weaning and sedation  were monitored according to st and ardized protocol -directed procedures . We collected data on physiological characteristics , mechanical ventilation duration , ICU and hospital stay , and mortality from the medical records data base . We assessed one-year mortality with a prospect i ve , st and ardized method . Multivariate logistic regression was performed to evaluate the association between weaning categories and outcome . RESULTS : We included 329 ventilation episodes , in which 115 patients passed at least one SBT . Thirty-four patients ( 30 % ) succeeded in their first SBT ( simple weaning group ) , 47 patients ( 40 % ) succeeded in their 2nd or 3rd SBT or in less than 7 days of weaning ( the difficult weaning group ) , and 34 patients ( 30 % ) required more than 3 SBTs or more than 7 days of weaning ( the prolonged weaning group ) . There were significant differences in ICU and hospital mortality between the simple , difficult , and prolonged-weaning groups . Prolonged weaning was an independent risk factor for longer ICU stay ( odds ratio 15.11 , 95 % CI 1.61–141.91 , P = .01 ) and hospital mortality ( odds ratio 3.66 , 95 % CI 0.99–13.51 ) . However , the weaning process did not impact one-year mortality ( odds ratio 2.61 , 95 % CI 0.82–8.35 ) . CONCLUSIONS : The new weaning classification system is clinical ly relevant and correlates to ICU and hospital mortality , but not to one-year mortality Because the clinics in a multiclinic r and omized clinical trial represent neither fixed stratification effects nor r and om classificatory effects , the appropriate analysis of data from such a trial has been the subject of controversy and debate . The following are some of the elements of controversy that are discussed and for which some bases for resolution are proposed . Is it ever valid to ignore the effects of clinics in the analysis ? Is it ever valid to drop clinics from the analysis ? Is a multiclinic clinical trial similar in structure or not to a single-clinic clinical trial in which patients have been stratified on a classificatory factor ? Assuming that clinics will be taken account of in the analysis , should it be the weighted or the unweighted average of within-clinic treatment differences that is to be taken as the best estimate of the overall difference between the treatments ? How should the data be analyzed if there is evidence of treatment-by-clinic interaction Weaning from mechanical ventilation was categorised as simple , difficult or prolonged by an international task force of the American Thoracic Society/European Respiratory Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine/Sociéte de Réanimation de Langue Française in 2007 . This new classification has not been tested in clinical practice . The objective of the present study was to determine the incidence and outcome of weaning according to the new categories . We included medical and surgical patients who required mechanical ventilation in a prospect i ve , multicentre , 6-month cohort study . From an initial cohort of 510 patients , 257 intubated patients started weaning .  Of these patients , the cumulative incidences of simple , difficult , and prolonged weaning were 152 ( 59 % ) , 68 ( 26 % ) and 37 ( 14 % ) , respectively . Hospital mortality was increased in patients with prolonged ( 32 % ) but not difficult ( 9 % ) weaning in comparison with those with simple weaning ( 13 % ) , overall p = 0.0205 . In a multivariate logistic regression model , prolonged but not difficult weaning was associated with an increased risk of death . Ventilator-free days and intensive care unit (ICU)-free days were decreased in both difficult and prolonged weaning . In conclusion , the new weaning category prolonged weaning is associated with increased mortality and morbidity in the ICU . The new category difficult to wean was associated with increased morbidity , but not mortality INTRODUCTION : Echocardiographic , electrocardiographic and other cardiorespiratory variables can change during weaning from mechanical ventilation . OBJECTIVES : To analyze changes in cardiac function , using Doppler echocardiogram , in critical patients during weaning from mechanical ventilation  , using two different weaning methods : pressure support ventilation and T‐tube ; and comparing patient subgroups : success vs. failure in weaning . METHODS : R and omized crossover clinical trial including patients under mechanical ventilation for more than 48 h and considered ready for weaning . Cardiorespiratory variables , oxygenation , electrocardiogram and Doppler echocardiogram findings were analyzed at baseline and after 30 min in pressure support ventilation and T‐tube . Pressure support ventilation vs. T‐tube and weaning success vs. failure were compared using ANOVA and Student 's t‐test . The level of significance was p<0.05 . RESULTS : Twenty‐four adult patients were evaluated . Seven patients failed at the first weaning attempt . No echocardiographic or electrocardiographic differences were observed between pressure support ventilation and T‐tube . Weaning failure patients presented increases in left atrium , intraventricular septum thickness , posterior wall thickness and diameter of left ventricle and shorter isovolumetric relaxation time . Successfully weaned patients had higher levels of oxygenation . CONCLUSION : No differences were observed between Doppler echocardiographic variables and electrocardiographic and other cardiorespiratory variables  during pressure support ventilation and T‐tube .  However cardiac structures were smaller , isovolumetric relaxation time was larger , and oxygenation level was greater in successfully weaned patients PURPOSE The purpose of this article was to investigate the effect of an additional 1-hour T-piece trial at the level of minimum pressure support ( PSmin ) on weaning outcome . MATERIAL S AND METHODS Open , r and omized , prospect i ve study of 44 patients who had received mechanical ventilation for more than 3 days . Thirty-six patients satisfied the protocol . There were 42 weaning trials . The patients were r and omized into an intervention group ( additional 1-hour period of T-piece trial ) and a control group ( extubation directly ) at PSmin . Blood gas analysis and estimation of respiratory and hemodynamic variables  were performed at the 15 cm H2O level of pressure support . Measurements were repeated at PSmin and during weaning process ( in intervention group ) . RESULTS Mean PSmin level was 7.6 ( + /- 1.9 ) cm H2O . There were no differences in total ventilation time ( TVT ) , acute physiology and chronic health evaluation ( APACHE ) II score , nutritional indices , and respiratory mechanics on PSmin between the two groups . The weaning success rate and the reintubation rate were similar for the intervention group ( 55 % and 18 % , respectively ) and control group ( 70 % and 20 % , respectively ) . Work of breathing , pressure time product , and tidal volume significantly worsened after a 1-hour T-piece trial when compared with those values measured at PSmin in the intervention group ( P < .05 ) . For the combined patient sample , TVT and tidal volume at PSmin were significantly different between the patients with weaning success ( 246 + /- 195 hours , 0.43 + /- 0.11 L ) and those with weaning failure ( 407 + 
    Output:
    