Comparison of two methods of measuring gastric pH

To assess the agreement between two methods of measuring gastric pH in critically ill patients (multiple band litmus paper-tested aspirations versus a meter-read probe located in the tip of a nasogastric tube) and to compare nurse satisfaction with both methods of measuring pH.

Prospective, correlational, nonprobability sample.

Mid-Atlantic, semirural Veterans Affairs Medical Center.

39 male, surgical, critical care patients, who were nasogastrically intubated in the operating room and received nothing by mouth. NURSES: Twenty-seven registered nurses on the medical-surgical intensive care staff.

Differences in pH units as determined by two methods of measurement and nurse satisfaction scores.

Litmus paper-tested aspirations versus a meter-read probe located in the tip of the nasogastric tube, measured every 2 hours for 48 hours. A nurse satisfaction assessment form for both measurement methods at entry, 6 months, and 12 months.

All measures of association, Pearson's r (0.79), the concordance coefficient (0.74), and eta (0.88), were high. The concordance coefficient measures indicated sufficient agreement between the two methods at the initial and 24 hour measurement times (Cb) = 0.97, 0.97, and 0.94), but not at 48 hours. The meter method indicated prophylaxis was needed when the paper did not, more often than did the paper method (9.3% vs 5.2%). A significant difference between methods was found only at the last reading at 48 hours (z = -2.24, p < .0249). MANOVA revealed that nurses' preference for the meter method was significant (F = 139.48, df = 1.18) and increased over time (F = 4.77, df = 2,36).

The gastric probe method of measuring pH is an accurate substitution up to 48 hours for the litmus-paper aspiration method in the postoperative patient who is receiving nothing by mouth. Nurses prefer the gastric probe method of measuring pH over the litmus-paper method because they judge it to be safer, faster, and more accurate.