Increased gastric PCO2 during exercise is indicative of gastric ischaemia: a tonometric study

Abstract

Background: Diagnosis of gastric ischaemia is difficult and angiography is an invasive procedure. Angiographic findings may not correlate with clinical importance.

Aims: To investigate whether tonometric measurement of intragastric PCO2 during exercise can be used to detect clinically important gastric ischaemia.

Methods: Fourteen patients with unexplained abdominal pain or weight loss were studied. Splanchnic angiography served as the gold standard. Three patients were studied again after a revascularisation procedure. Gastric PCO2 was measured from a nasogastric tonometer, with 10 minute dwell times, and after acid suppression. Gastric and capillary PCO2 were measured before, during, and after submaximal exercise of 10 minutes duration.

Results: Seven patients had normal angiograms; seven had more than 50% stenosis in the coeliac (n=7) or superior mesenteric artery (n=4). Normal subjects showed no changes in tonometry. In patients with stenoses, the median intragastric PCO2 (PiCO2) at rest was 5.2 kPa (range 4.8-11.2) and rose to 6.4 kPa (range 5.7-15.7) at peak exercise; the median intragastric blood PCO2 gradient increased from 0.0 kPa (range -0.8 to 5.9) to 1.7 kPa (range 0.9 to 10.3; p<0.01). Only two subjects had abnormal tonometry at rest; all had supernormal values at peak exercise. The PCO2 gradient correlated with clinical and gastroscopic severity; in patients reexamined after revascularisation (n=3), exercise tonometry returned to normal.

Conclusion: Gastric tonometry during exercise is a promising non-invasive tool for diagnosing and grading gastrointestinal ischaemia and evaluating the results of revascularisation surgery for symptomatic gastric ischaemia.

Figure 1

The intragastric-blood PCO₂ gradient, before, during, and after exercise in (A) patients with splanchnic stenosis on angiography (n=7) and (B) patients with normal angiograms (n=7). The dotted line represents the upper level of normal, established in healthy volunteers (Kolkman et al²⁰). Baseline (resting) values at t=−10 minutes; exercise test by stepping stairs from t=0 to 10 minutes (grey square); recovery phase at t=20, t=30, and t=50 minutes.

Figure 2

Correlation between tonometry and severity of ischaemia in patients with splanchnic stenosis. (A) Peak PCO₂ gradient versus symptom score (n=10; seven patients, three reexamined after surgery). (B) Peak PCO₂ gradient versus gastroscopic score (n=9; seven patients, two reexamined after surgery).