title: Pulmonary gas exchange response to weaning with pressure-support ventilation in exacerbated chronic obstructive pulmonary disease patients.
abstract: OBJECTIVE
  To assess if pressure-support ventilation (PSV) can improve ventilation-perfusion (V(A)/Q) imbalance observed during the transition from positive-pressure ventilation to spontaneous breathing in intubated chronic obstructive pulmonary disease (COPD) patients during weaning.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Respiratory intensive care unit of a tertiary university hospital.
  
  
  METHODS
  Seven mechanically ventilated COPD male patients (age 68+/-6 (SD) years; FEV(1) 26+/-6% predicted) during weaning.
  
  
  METHODS
  Patients were studied during three ventilatory modalities: (1) assist-control ventilation (ACV), tidal volume (V(T)), 8-10 ml. kg(-1); (2) PSV aimed to match V(T)in ACV, 15+/-1 cmH(2)O and (3) spontaneous breathing.
  
  
  RESULTS
  Arterial and mixed venous respiratory blood gases, V(A)/Q distributions, hemodynamics and breathing pattern were measured. Compared with both ACV and PSV, during spontaneous breathing patients exhibited decreases in V(T) (of 43%, p<0.001) and increases in respiratory rate (of 79%, p<0.001), PaCO(2) (of 8.5 mmHg, p=0.001), cardiac output (of 27%, p<0.001) and mixed venous oxygen tension (of 3.4 mmHg, p=0.003), while PaO(2) remained unchanged throughout the study. Except for a shift of the pulmonary blood flow distribution to areas with lower V(A)/Q ratios (p=0.044) and an increase of dead space (of 25%, p=0.004) during spontaneous breathing, no other changes in V(A)/Q distributions occurred. No differences were shown between ACV and PSV modalities.
  
  
  CONCLUSIONS
  In COPD patients during weaning, PSV avoided V(A)/Q worsening during the transition from positive-pressure ventilation to spontaneous breathing. Hemodynamics, blood gases or V(A)/Q mismatch were no different between ACV and PSV when both modalities provided similar levels of ventilatory assistance.
authors.affiliation: Servei de Pneumologia i Al.lérgia Respiratòria, Institut Clínic de Pneumologia i Cirurgia Toràcica, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic, Universitat de Barcelona, 08036, Barcelona, Spain. miferrer@clinic.ub.es
authors.forename: Miquel
authors.initials: M
authors.lastname: Ferrer
authors.forename: Raquel
authors.initials: R
authors.lastname: Iglesia
authors.forename: Josep
authors.initials: J
authors.lastname: Roca
authors.forename: Felip
authors.initials: F
authors.lastname: Burgos
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
authors.forename: Robert
authors.initials: R
authors.lastname: Rodriguez-Roisin
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D006439:Hemodynamics; D006801:Humans; D007362:Intensive Care Units; D007442:Intubation, Intratracheal; D008297:Male; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D012121:Respiration, Artificial / Q000379:methods*; D018709:Statistics, Nonparametric; D015300:Ventilator Weaning