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A new method for continuous tonometric pCO2 measurement - in vitro studies.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
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1999 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 20, no 2, 129-136 p.Article in journal (Refereed) Published
Abstract [en]

The available methods for tonometric pCO2 measurement only provide the possibility of performing intermittent registrations. A new method allowing continuous tonometric pCO2 measurement has been developed and tested in an in vitro model. A standard tonometer for intestinal pCO2 measurement was modified to allow continuous perfusion of the balloon with physiological saline solution in a closed system. The pCO2 in the system was determined in a specially constructed measurement chamber with a TCM20 percutaneous pCO2 monitor. In this in vitro model the tonometer balloon was placed in a saline bath with a constant pCO2 concentration and the measurements from the closed circulating system were compared with those obtained from a standard tonometer placed in the same bath. In 8 and 24 h experiments the circulating system measured the pCO2 value as accurately and reliably as traditional tonometry. This study indicates that the new method makes continuous monitoring of pCO2 possible.

Place, publisher, year, edition, pages
1999. Vol. 20, no 2, 129-136 p.
Keyword [en]
tonometry, continuous, pCO2 measurement
URN: urn:nbn:se:umu:diva-4409DOI: 10.1088/0967-3334/20/2/002PubMedID: 10390015OAI: diva2:143502
Available from: 2005-02-24 Created: 2005-02-24 Last updated: 2012-03-27Bibliographically approved
In thesis
1. Exploring Intestinal Ischemia: An experimental study
Open this publication in new window or tab >>Exploring Intestinal Ischemia: An experimental study
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background and aims: Unrecognized intestinal mucosal ischemia in severely ill patients may trigger development of multiple organ failure. Such ischemia can be evaluated by intraluminal tonometry reflecting mucosal PCO2 and intramucosal pH (pHi). The aims were to develop an apparatus for continuous saline tonometry (CST), to analyse circulatory control mechanisms during intestinal hypoperfusion and to evaluate the effect of dopexamine on intestinal circulation.

Methods: A modified standard tonometry catheter was integrated in a closed system with circulating saline. By measuring saline PCO2 in a measurement unit pHi could be calculated. This novel system was tested in vitro and in vivo. In a porcine study, CST was evaluated against standard saline tonometry, tissue oxygenation (PO2 TISSUE), jejunal mucosal perfusion (laser doppler flowmetry; LDF) and mesenteric net lactate flux during graded reductions of superior mesenteric arterial pressure (PSMA). Local control mechanisms for maintenance of intestinal oxygenation were analysed. Effects of dopexamine on the intestinal vascular bed were explored. Mucosal lactate production was assessed by microdialysis.

Results: CST measured accurate PCO2 values and changes in pHi during restricted intestinal circulation and at reperfusion. Local control mechanisms were insufficient at a PSMA of 30 mmHg, pHi was reduced to 7.10 and intestinal net lactate production was demonstrated. Absence of anaerobic intestinal metabolism was verified at PSMA ≥ 50 mmHg, pHi ≥ 7.22 and a PCO2 gap ≤ 15.8 mmHg. Dopexamine induced negative regional metabolic effects at the lowest PSMA, as expressed by decreased PO2 TISSUE and pHi, increased PCO2 gap and intestinal net lactate production.

Conclusions: CST reflected changes in pHi, induced by intestinal hypoperfusion and at reperfusion. Levels of PSMA, pHi and PCO2 gap as indicators of aerobic conditions were defined. Dopexamine induced a decrease of PO2 TISSUE and pHi as well as an increase in lactate flux at the lowest PSMA level.

Place, publisher, year, edition, pages
Umeå: Kirurgisk och perioperativ vetenskap, 2005. 59 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 938
Surgery, gastrointestinal tonometry, continuous, pig, pHi, intestinal ischemia, intestinal vascular bed, lactate, tissue oxygen tension, microdialysis, dopexamine, Kirurgi
National Category
Research subject
urn:nbn:se:umu:diva-461 (URN)91-7305-788-6 (ISBN)
Public defence
2005-03-19, B, Tandläkarhögskolan, 9tr, Norrlands Universitetssjukhus, Umeå, 10:00 (English)
Available from: 2005-02-24 Created: 2005-02-24 Last updated: 2009-11-13Bibliographically approved

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