GASTRIC TONOMETRY - IN-VIVO COMPARISON OF SALINE AND AIR TONOMETRY INPATIENTS WITH CARDIOGENIC-SHOCK

Measurement of gastric intramucosal pH (pHi) has been advocated to ass ess gastric perfusion. Regional Pco(2) (rPco(2)) values are measured u sing saline tonometry (rsPco(2))and more recently using air tonometry (raPco(2)). We compared 237 measurements of saline and air tonometry i n 19 consecutive, severely ill patients (mean age 59 (range 31-76) yr, 19 males, APACHE 11 22+/-7) with cardiogenic shock. Equilibration per iod was set to 90 min. Nineteen independent paired samples of mean raP co(2) and mean rsPco(2) of each patient showed good correlation (r=0.9 3, P < 0.001). Mean raPco(2) was 6.5 (1.8) kPa and mean rsPco(2) 6.8 ( 2.4) kPa. Pco(2) measured by saline was significantly higher than that measured by air (P < 0.05). Bland and Altman analysis showed a bias ( mean rsPco(2)-mean raPco(2)) of 0.3 kPa and a precision of 1.2 kPa. Ag reement between the two methods decreased with increasing rPco(2) conc entrations. Although air tonometry of rPco(2) is a promising technique , a systematic disagreement with saline tonometry at high rPco(2) valu es requires further investigation and cautious interpretation of these values.