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Comparison of gastric air tonometry with standard saline tonometry



To compare partial pressure of carbon dioxide (PCO2) measurements obtained by sampling gastric intraluminal air with those obtained by standard saline tonometry.


Prospective, unblinded study.


Intensive care unit in a tertiary cardiac surgical center.


20 patients undergoing cardiac surgery.


Gastric tonometric catheters were inserted, gastric fluid was aspirated, and 100 cc of air was injected into the stomach.


After an equilibration period of 30 min, samples of gastric air and saline were anaerobically aspirated and analyzed on a standard blood gas machine. The reproducibility of PCO2 measurements in a given patient was assessed by analyzing consecutive samples of gastric air and calculating the coefficient of variation (CV).


PCO2 values measured in samples of gastric air (PCO2air) were highly correlated with those derived by saline tonometry (PCO2ss)(r 2=0.95,p=0.0001); PCO2air was significantly greater than PCO2ss (50±17 vs 48±17 mmHg,p=0.0001). Intramucosal pH (pHi) calculated from PCO2 air was significantly lower than that calculated from PCO2ss (7.26±0.23 vs 7.28±0.24,p=0.0001). Analysis of intermethod differences showed significant bias for both PCO2 (2.4±7.6 mmHg, mean±2SD, bias±precision) and pHi (−0.023±0.074, mean±2SD, bias±precision). The within-subject variability of replicate PCO2 measurements in gastric air was low (CV=2.6±0.8).


We conclude that intraluminal PCO2 can be accurately determined in postoperative cardiac surgery patients by instilling air into the stomach and analyzing samples of gastric air on a standard blood gas machine. In comparison with saline tonometry, air tonometry consistently yields lower pHi values.

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  1. 1.

    Fiddian-Green RG (1994) Management of gastric intramucosal acidosis. In: Vincent JL (ed) Yearbook of intensive care and emergency medicine. Springer, Berlin pp 217–224

  2. 2.

    Doglio GR, Pusajo JF, Egurrola MA, Bonfigli GC, Parra C, Vetere L, Hernandez MS, Fernandez S, Palizas F, Gutierrez G (1991) Gastric mucosal pH as a prognostic index of mortality in critically ill patients. Crit Care Med 19: 1037–1040

  3. 3.

    Gutierrez G, Paliza F, Doglio G, Wainsztein N, Gallesio A, Pacin J, Dubin A, Schiavi E, Jorge M, Pusajo J, Klein F, San Roman E, Dorfman B, Shottlender J, Giniger R (1992) Gastric intramucosal pH as therapeutic index of tissue oxygenation in critically ill patients. Lancet 339: 195–199

  4. 4.

    Fiddian-Green RG, Baker S (1987) Predictive value of the stomach wall pH for complications after cardiac operations: comparison with other monitoring. Crit. Care Med 15: 153–156

  5. 5.

    Bland JM, Altman DG (1986) Statistical methods for assessing agreement between two methods of clinical measurement. Lancet I 307–310

  6. 6.

    Riddington D, Venkatesh B, Cluton-Brock T, Bion J (1992) Potential hazards in estimation of gastric intramucosal pH. Lancet 340: 547

  7. 7.

    Riddington D, Venkatesh KB, Cluton-Brock T, Bion J (1994) Measuring carbon dioxide tension in saline and alternative solutions: quantification of bias and precision in two blood gas analyzers. Crit Care Med 22: 96–100

  8. 8.

    Takala J, Parviainen I, Siloaho M, Ruokonen E, Hamalainen E (1994) Saline PCO2 is an important source of error in the assessment of gastric intramucosal pH. Crit Care Med 22: 1877–1879

  9. 9.

    Knichwitz G, Mertes N, Kuhmann M (1995) Improved PCO2 measurement in six standard blood gas analysers using a phosphate-buffered solution for gastric tonometry. Anesthesia 50: 532–534

  10. 10.

    Eichelbronner O, Feist H, Radermcaher P (1995) Reliability of tonometric intramucosal PCO2 measurement with a phosphate-buffer solution. Intensive care Med 21: 387–388

  11. 11.

    Knichwitz G, Kuhmann M, Brodner G, Brussel T (1995) Gastric tonometry: precision and reliability are improved by a phosphate buffered solution (abstract). Anesthesiology 83: A239

  12. 12.

    Salzman AL, Strong KE, Wang H, Wollert PS, Vandermeer TJ, Fink MP (1994) Intraluminal “balloonless” air tonometry: a new method for determination of gastrointestinal mucosal carbon dioxide tension. Crit Care Med 22: 126–134

  13. 13.

    Tang W, Weil MH, Sun S, Marko N, Gazmuri RJ, Bisera J (1994) Gastric intramural PCO2 as monitor of perfusion failure during hemorrhagic and anaphylactic shock. J Appl Physiol 76: 572–577

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Correspondence to G. Tzelepis.

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Tzelepis, G., Kadas, V., Michalopoulos, A. et al. Comparison of gastric air tonometry with standard saline tonometry. Intensive Care Med 22, 1239–1243 (1996).

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Key words

  • Tonometry
  • Intramucosal pH
  • Gastric air
  • Carbondioxide