title: Proportional assist versus pressure support ventilation: effects on breathing pattern and respiratory work of patients with chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  To investigate the breathing pattern and the inspiratory work of breathing (WOB(I)) in patients with chronic obstructive pulmonary disease (COPD) assisted with proportional assist ventilation (PAV) and conventional pressure support ventilation (PSV).
  
  
  METHODS
  Prospective controlled study.
  
  
  METHODS
  Intensive care unit of a university hospital.
  
  
  METHODS
  Thirteen COPD patients being weaned from mechanical ventilation.
  
  
  METHODS
  All patients were breathing PSV and two different levels of PAV.
  
  
  RESULTS
  During PAV (EVITA 2 prototype, Dräger, Germany), the resistance of the endotracheal tube (R(et)) was completely compensated while the patients' resistive and elastic loads were compensated for by approximately 80 % and 50 % (PAV(80) and PAV(50)), respectively. PSV was adjusted to match the same mean inspiratory pressure (Pinsp(mean)) as during PAV(80). Airway pressure, esophageal pressure and gas flow were measured over a period of 5 min during each mode. Neuromuscular drive (P(0.1)) was determined by inspiratory occlusions. Mean tidal volume (V(T)) was not significantly different between the modes. However, the coefficient of variation of V(T) was 10 +/- 4.%, 20 +/- 13 % and 15 +/- 8 % during PSV, PAV(80) and PAV(50), respectively. Respiratory rate (RR) and minute ventilation (V(E)) were significantly lower during PAV(80) as compared with both other modes, but the differences did not exceed 10 %. PAV(80) and PSV had comparable effects on WOB(I) and P(0.1), whereas WOB(I) and P(0.1) increased during PAV(50) compared with both other modes.
  
  
  CONCLUSIONS
  Mean values of breathing pattern did not differ by a large amount between the investigated modes. However, the higher variability of V(T) during PAV indicates an increased ability of the patients to control V(T) in response to alterations in respiratory demand. A reduction in assist during PAV(50) resulted in an increase in WOB and indices of patient effort.
authors.affiliation: Klinik und Poliklinik für Anaesthesiologie und Spezielle Intensivmedizin, Rheinische Friedrich-Wilhelms-Universität Bonn, Sigmund-Freud-Strasse 25, D-53 105 Bonn, Germany. hwrigge@uni-bonn.de
authors.forename: H
authors.initials: H
authors.lastname: Wrigge
authors.forename: W
authors.initials: W
authors.lastname: Golisch
authors.forename: J
authors.initials: J
authors.lastname: Zinserling
authors.forename: M
authors.initials: M
authors.lastname: Sydow
authors.forename: G
authors.initials: G
authors.lastname: Almeling
authors.forename: H
authors.initials: H
authors.lastname: Burchardi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012119:Respiration; D012121:Respiration, Artificial / Q000379:methods