title: Influence of prone position on gastric mucosal-arterial PCO2 gradients.
abstract: OBJECTIVE
  To evaluate the effects of mechanical ventilation in the prone position on gastric mucosal-arterial PCO2 gradients.
  
  
  METHODS
  Prospective clinical study.
  
  
  METHODS
  Intensive care unit in a university clinic.
  
  
  METHODS
  Twenty-five patients requiring mechanical ventilation. The physician in charge indicated the turning manoeuver for the individual patient.
  
  
  RESULTS
  In addition to routine measurements of global hemodynamics and gas exchange we determined: 1) intragastric pressure; and 2) gastric mucosal-arterial PCO2 difference. After a baseline measurement in the supine position patients were turned to the prone position. After 60', 120', a median of 6.5 h (2-10 h) in the prone position, and again after 60' in the supine position, all measurements were repeated. Global hemodynamics remained unaltered throughout the study. While gastric mucosal-arterial PCO2 gradients did not change significantly during the first 60 min in the prone position, they significantly increased during the following 60 min [median/percentile: baseline: 6 (1 to -3); 60': 7 (15-5); 120': 13 (20-8) mmHg]. The median intragastric pressure was not significantly affected [baseline: 10 (13-5); 60': 12 (16-8); 120': 11 (13-7) mmHg], but 9 of the 11 patients in whom intragastric pressure increased during the first 60 min in the prone position also showed significantly increased PCO2 gradients (P < 0.01).
  
  
  CONCLUSIONS
  Mechanical ventilation in the prone position may be affiliated with increased tonometric gastric mucosal-arterial PCO2 gradients depending on the effect on intraabdominal pressure. Measuring intraabdominal pressure and/or gastric mucosal PCO2 via a nasogastric tube therefore may help to detect adverse effects of this ventilatory strategy.
authors.affiliation: Universität Ulm, Universitätsklinik für Anästhesiologie, Donau, Germany. Peter.Kiefer@medizin.uni-ulm.de
authors.forename: P
authors.initials: P
authors.lastname: Kiefer
authors.forename: A
authors.initials: A
authors.lastname: Morin
authors.forename: C
authors.initials: C
authors.lastname: Putzke
authors.forename: H
authors.initials: H
authors.lastname: Wiedeck
authors.forename: M
authors.initials: M
authors.lastname: Georgieff
authors.forename: P
authors.initials: P
authors.lastname: Radermacher
mesh_terms: D000704:Analysis of Variance; D002245:Carbon Dioxide / Q000097:blood*; D005753:Gastric Mucosa / Q000098:blood supply* / Q000378:metabolism*; D006439:Hemodynamics; D006801:Humans; D010313:Partial Pressure; D016684:Prone Position; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000379:methods*; D013152:Splanchnic Circulation; D018709:Statistics, Nonparametric
chemical_list: D002245:Carbon Dioxide