Intensive Care Medicine

, Volume 25, Issue 3, pp 269–273 | Cite as

Influence of alveolar ventilation changes on calculated gastric intramucosal pH and gastric-arterial PCO2 difference

  • G. Bernardin
  • P. Lucas
  • H. Hyvernat
  • P. Deloffre
  • M. Mattéi

Abstract

Objective: To evaluate the influence of changes in alveolar ventilation on the following tonometry-derived variables: gastric intramucosal CO2 tension (PtCO2), gastric arterial CO2 tension difference (PgapCO2), gastric intramucosal pH (pHi) and arterial pH-pHi difference (pHgap). Design: Clinical prospective study. Setting: A medical intensive care unit in a university hospital. Patients: Ten critically ill, mechanically ventilated patients requiring hemodynamic monitoring with pulmonary artery catheter. Interventions: Gastric tonometer placement. A progressive increase in tidal volume (VT) from 7 to 10 ml/kg followed by an abrupt return to baseline VT level. Measurements and main results: Tonometer saline PtCO2 and hemodynamic data were collected hourly at various VT levels: H0 and H0' (baseline VT = 7 ml/kg), H1 (VT = 8 ml/kg), H2 (VT = 9 ml/kg), H3 (VT = 10 ml/kg), H4 (baseline VT). During the “hyperventilation phase” (H0-H3), pHi (p < 0.01) and pHgap (p < 0.05) increased but PgapCO2 remained unchanged. Cardiac output (CO) was not affected by ventilatory change. During the “hypoventilation phase” (H3-H4), pHi fell from 7.27 ± 0.11 to 7.23 ± 0.09 (p < 0.01) and PgapCO2 decreased from 16 ± 5 mmHg to 13 ± 4 mmHg (p < 0.05). VT reduction was associated with a significant cardiac output elevation (p < 0.05). Conclusions: PaCO2 and PtCO2 are similarly influenced by the changes in alveolar ventilation. Unlike pHi, the PgapCO2 is not affected by ventilation variations unless CO changes are associated.

Key words Gastric intramucosal pH Tonometry Alveolar ventilation Gut perfusion 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • G. Bernardin
    • 1
  • P. Lucas
    • 1
  • H. Hyvernat
    • 1
  • P. Deloffre
    • 1
  • M. Mattéi
    • 1
  1. 1.Service de Réanimation Médicale, Hôpital de l'Archet, BP 3079, F-06 202 Nice Cedex 3, France e-mail: gbernard@unice.fr Tel. + 3 34 92 03 55 10 Fax + 3 34 92 03 56 07FR

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