title: Tracheal gas insufflation during late exhalation efficiently reduces PaCO(2) in experimental acute lung injury.
abstract: OBJECTIVE
  Tracheal gas insufflation (TGI) reduces PaCO(2) by flushing the tracheal and mechanical deadspace, and may have its maximum benefit when TGI gas is unopposed by significant expiratory gas flow. Thus, limiting TGI to the late expiratory period may diminish tracheal exposure to TGI gas while preserving the efficacy of TGI. This study examined the gas exchange consequences of such late-expiratory TGI.
  
  
  METHODS
  Randomized controlled trial, animal study.
  
  
  METHODS
  Eleven pigs.
  
  
  METHODS
  After stable lung injury was established using oleic acid 11 pigs were ventilated using a standardized lung protective strategy. Phasic expiratory TGI was applied for 30 min stages during the last 20%, 40%, 60%, and 100% of expiration in random sequence. PaCO(2) was continuously measured via an indwelling blood gas analysis system.
  
  
  RESULTS
  PaCO(2) at baseline was 86.1+/-4.7 mmHg, and decreased progressively with increasing TGI duration of 20%, 40%, and 60%, but not 100%, of expiration (PaCO(2)=75.7+/-5.2, 68.8+/-3.6, 65.1+/-5.3 and 65.2+/-5.2 mmHg, respectively). For all stages the reduction in PaCO(2) relative to baseline was significant. Trends of increasing PaO(2) and airway pressure with increasing TGI duration were noted and most likely associated with a TGI-induced increase in lung volume.
  
  
  CONCLUSIONS
  Under these conditions confining TGI to the final 60% of expiration achieved effective PaCO(2) reduction, not significantly different from panexpiratory TGI, while limiting exposure of the trachea to TGI gas, and reducing the potential for TGI-induced hyperinflation. These findings suggest that TGI is most effectively applied in a phasic manner in late expiration, with its duration titrated to effect.
authors.affiliation: Regions Hospital, Pulmonary Research, 640 Jackson Street, St. Paul, MN 55101, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Carter
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Adams
authors.forename: Mary
authors.initials: M
authors.lastname: Stone
authors.forename: Peter
authors.initials: P
authors.lastname: Bliss
authors.forename: John R
authors.initials: JR
authors.lastname: Hotchkiss
authors.forename: John J
authors.initials: JJ
authors.lastname: Marini
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000097:blood*; D004195:Disease Models, Animal; D007327:Insufflation / Q000009:adverse effects / Q000379:methods*; D008168:Lung; D010313:Partial Pressure; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000097:blood / Q000628:therapy*; D013552:Swine; D014132:Trachea
chemical_list: D002245:Carbon Dioxide