title: Effect of mechanical ventilation on microvascular perfusion in critical care patients.
abstract: OBJECTIVE
  Microvascular perfusion, pivotal for adequate tissue oxygenation is potentially linked to outcome in critical care therapy. Mechanical ventilation (MV) and positive end-expiratory pressure (PEEP) as standard concepts of respiratory management are known to have deleterious effects on regional organ perfusion especially in the splanchnic area. As these effects have been attributed to different physiologic mechanisms, the purpose of this study was to investigate the effect of positive pressure ventilation on extra-abdominal tissue perfusion in non-surgical intensive care patients.
  
  
  METHODS
  Sublingual microcirculation was evaluated in 46 severely ill patients (group 1: n=26 requiring MV and PEEP; group 2: n=20 spontaneous breathing) admitted to the intensive care unit using sidestream darkfield intravitalmicroscopy. According to current guidelines, sublingual vessels were categorized by means of size and flow in semi-quantitative categories determining microvascular flow index (MFI). Total microvascular flow index (TMFI) was calculated for each patient as mean value of flow in all vessel categories.
  
  
  RESULTS
  No significant difference was observed between both groups in microvascular flow index in each vessel category and in total microvascular flow index. Patients requiring mechanical ventilation presented with more comorbidities and higher acuity of illness scores resulting in a higher ICU mortality, which however was not accompanied by microcirculatory differences at the time of measurement.
  
  
  CONCLUSIONS
  Mechanical ventilation and PEEP have no general deleterious effects on microvascular perfusion of the sublingual mucosa. However, further clinical studies are required to investigate potential effects of higher levels of ventilation pressure or PEEP on microvascular perfusion.
authors.affiliation: Department of Internal Medicine I (Cardiology, Angiology, Pneumology), Friedrich-Schiller University, Jena, Germany. alexander.lauten@med.uni-jena.de
authors.forename: Alexander
authors.initials: A
authors.lastname: Lauten
authors.forename: Markus
authors.initials: M
authors.lastname: Ferrari
authors.forename: Ruediger
authors.initials: R
authors.lastname: Pfeifer
authors.forename: Bjoern
authors.initials: B
authors.lastname: Goebel
authors.forename: Wilma
authors.initials: W
authors.lastname: Rademacher
authors.forename: Florian
authors.initials: F
authors.lastname: Krizanic
authors.forename: Christoph
authors.initials: C
authors.lastname: Roediger
authors.forename: Hans R
authors.initials: HR
authors.lastname: Figulla
authors.forename: Christian
authors.initials: C
authors.lastname: Jung
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003422:Critical Care; D005260:Female; D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D009060:Mouth Floor / Q000098:blood supply*; D012039:Regional Blood Flow; D012121:Respiration, Artificial