Reliability of intrabladder pressure measurement in intensive care

The reliability of intrabladder pressure measurements obtained in nonsupine patients is unknown. To investigate the reliability of measurements of intrabladder pressure obtained with 30 degrees head-of-bed elevation. With patients supine, 30 degrees head-of-bed elevation, and instillation of 0 and 25 mL physiological saline, intrabladder pressure was measured in 10 patients: twice by one nurse to assess intraobserver reliability and once by a different nurse to assess interobserver reliability. Data were analyzed by using paired t tests, Pearson correlation, and Bland-Altman analysis. For intraobserver reliability, measurements obtained with no instillation (mean difference, -1.8; 95% confidence interval [CI], -4.9 to 1.3; P = .22) and with instillation of 25 mL (mean difference, -0.6; 95% CI, -1.8 to 0.6; P = .28) did not differ significantly. Pearson r values were 0.74 and 0.81, respectively. Estimated Bland-Altman bias and limits of agreements were -1.8 and -10.3 to 6.7 mm Hg and -0.6 and -3.82 to 2.62 mm Hg, respectively. For interobserver reliability, measurements obtained with no instillation (mean difference, 1.0; 95% CI, -2.2 to 4.2; P = .49) and with instillation of 25 mL (mean difference, -0.7; 95% CI, -2.45 to 1.05; P = .39) did not differ significantly. Pearson r values were 0.78 and 0.82, respectively. Estimated Bland-Altman bias and limits of agreement were 1.0 and -7.76 to 9.76 mm Hg and -0.7 and -5.5 to 4.0 mm Hg, respectively. Reliability of intrabladder pressure measurements obtained with 30 degrees head-of-bed elevation is strong.