title: Physiological comparison of three spontaneous breathing trials in difficult-to-wean patients.
abstract: OBJECTIVE
  To compare cardiovascular and respiratory responses to different spontaneous breathing trials (SBT) in difficult-to-wean patients using T-piece and pressure support ventilation (PSV) with or without positive end-expiratory pressure (PEEP).
  
  
  METHODS
  Prospective physiological study. Fourteen patients who were monitored with a Swan-Ganz catheter and had failed a previous T-piece trial were studied. Three SBTs were performed in random order in all patients: PSV with PEEP (PSV-PEEP), PSV without PEEP (PSV-ZEEP), and T-piece. PSV level was 7 cmH(2)O, and PEEP was 5 cmH(2)O. Inspiratory muscle effort was calculated, and hemodynamic parameters were measured using standard methods. RESULTS [MEDIAN (AND INTERQUARTILE RANGE)]: Most patients succeeded in the PSV-PEEP (11/14) and PSV-ZEEP (8/14) trials, but all failed the T-piece trial. Patient effort was significantly higher during T-piece than during PSV with or without PEEP [esophageal pressure-time product was 292 (238-512), 128 (58-299), and 148 (100-465) cmH(2)O x s/min, respectively, p < 0.05]. Left ventricular heart failure was observed in 11 of the 14 patients during the T-piece trial. Pulmonary artery occlusion pressure and respiratory rate were significantly higher during T-piece than with PSV-PEEP [21 (18-24) mmHg versus 17 (14-22) mmHg, p < 0.05 and 27 (21-35) breaths/min versus 19 (16-29) breaths/min, p < 0.05 respectively]. Tidal volume was significantly lower during the T-piece trial.
  
  
  CONCLUSIONS
  In this selected population of difficult-to-wean patients, PSV and PSV plus PEEP markedly modified the breathing pattern, inspiratory muscle effort, and cardiovascular response as compared to the T-piece. Caregivers should be aware of these differences in SBT as they may play an important role in weaning decision-making.
authors.affiliation: Servei de Medicina Intensiva, Hospital Santa Creu i Sant Pau, C. Sant Quintí 89, 08041, Barcelona, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Cabello
authors.forename: Arnaud W
authors.initials: AW
authors.lastname: Thille
authors.forename: Ferran
authors.initials: F
authors.lastname: Roche-Campo
authors.forename: Laurent
authors.initials: L
authors.lastname: Brochard
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Gómez
authors.forename: Jordi
authors.initials: J
authors.lastname: Mancebo
mesh_terms: D000368:Aged; D002302:Cardiac Output / Q000502:physiology*; D002407:Catheterization, Swan-Ganz; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods; D011175:Positive-Pressure Respiration / Q000295:instrumentation / Q000379:methods*; D011446:Prospective Studies; D015656:Respiratory Mechanics / Q000502:physiology; D016019:Survival Analysis; D016896:Treatment Outcome; D015300:Ventilator Weaning / Q000295:instrumentation / Q000379:methods*